Adjuvant Melatonin for Uveal Melanoma (AMUM): Protocol for a Randomized Open-label Phase III Study

Abstract

Background

Uveal melanoma is the most common primary intraocular tumor in adults. In Sweden, 60 to 100 patients are diagnosed with the disease each year. Almost half of the patients develop metastases, with a median survival time of 1 year once metastases are detected. The primary ocular tumor is typically treated with either enucleation or brachytherapy, and no adjuvant treatment is added. Melatonin is an indolamine hormone that has improved survival in previous trials with patients diagnosed with various cancers, including advanced cutaneous melanoma. Side effects have been mild. We aim to investigate if adjuvant treatment with melatonin for 5 years following diagnosis of non-metastasized uveal melanoma can decrease the occurrence of metastases.

Methods

An open-label, prospective, 5-year randomized clinical trial (RCT) will be conducted at St. Erik Eye Hospital. Patients (n = 100) diagnosed with non-metastatic uveal melanoma will be included in this trial and randomized to either treatment with adjuvant melatonin 20 mg (4 tablets of 5 mg) at 10 pm for five years, or to standard follow-up (control group). The primary outcome measurement is the number of patients that have developed metastases 5 years after randomization. The secondary outcomes are overall survival, risk of developing other cancers, overall survival after detection of metastases, and differences in the occurrence of adverse events (AE) and serious adverse events (SAE) between the groups.

Discussion

Melatonin has been found to positively impact our immune system, inhibit angiogenesis, stimulate apoptosis in malignant cells, and act as a potent antioxidant. Previous clinical trials have used similar doses of melatonin with positive results, particularly in advanced stages of cancer. Previous animal and human studies have found the toxicity of the hormone to be low. Considering the potential benefits and limited risks of melatonin, as well as its global availability, it may be a suitable candidate for an adjuvant treatment in patients with uveal melanoma.

Trial registration

Our trial protocol has been approved and registered by the Swedish Medical Products Agency on June 22, 2022 (EudraCT 2022-500307-49-00). Our trial registration number is NCT05502900 and the date of registration is August 16, 2022.

Administrative Information

In this trial, 100 subjects with non-metastatic uveal melanoma will be randomized to either treatment with melatonin 20 mg at 10 pm for 5 years or to a control group. The main objective is to investigate whether treatment with melatonin can reduce the risk of developing metastases after 3 and 5 years. Only subjects at high risk for metastasis development will be included in the trial. As uveal melanoma has a relatively low incidence rate compared to other cancers, the recruitment period is estimated to take 3 to 4 years. 

Introduction

Background And Rationale

About 50% of patients diagnosed with uveal melanoma develop metastases, primarily in the liver.¹ This risk is consistent regardless of which method is chosen to treat the primary tumor.² The most common forms of treatment include enucleation (surgical removal of the tumor containing eye), proton beam irradiation, and plaque brachytherapy – a form of local radiation treatment. Due to very early seeding of micrometastases, the treatment choice typically does not affect the risk of dying from metastatic disease. Micrometastases are clusters of cancerous cells too small to be detected in standard radiological examinations, which migrate from the primary tumor to other organs, such as the liver, where they can remain latent for many years before growing into radiologically detectable tumors, or macrometastases.³ By the time these metastases are detected, the median survival time is one to two years.^4,5 This project’s objective is to investigate if adjuvant treatment with melatonin tablets, following diagnosis of the primary tumor, decreases the risk of developing macrometastases of uveal melanoma.

Previous randomized, placebo-controlled studies investigating various types of solid cancers including cutaneous melanoma have found that melatonin can improve 1-year survival significantly.⁶ A similar impact has been seen in a smaller study, where partial responses or stable disease progression was found in 12 of 40 patients (30%) with advanced cutaneous malignant melanoma taking melatonin after an average follow up of 5 weeks.⁷ In a third study, adjuvant treatment with melatonin following surgical resection of lymph node metastasized cutaneous malignant melanoma resulted in significantly fewer patients with progression after an average of 31 months compared to the placebo group.⁸ No melatonin-related toxicity was detected in the treatment groups. In a recently published study on patients with non-small cell lung cancer, a significantly improved progression-free survival was seen in a subgroup of patients with advanced stage disease, however, in another, similar study no such impact was seen after a year of treatment with melatonin.^9,10 The overarching factor responsible for melatonin's impact on cancer is believed to be related to its oncostatic properties, including inhibition of tumor cell proliferation, remodeling of the cytoskeleton, antioxidative effects, and stimulation of the immune system.^11–13

We have recently described the rationale for adjuvant treatment with melatonin for uveal melanoma in a review of the literature.¹⁴ Studies from 1997 and 1998 showed that melatonin can inhibit the growth of uveal melanoma cells with 41 to 50 in a concentration of 0.1 to 10 nM, compared to non-treated cells.^15,16 Melatonin’s precursors tryptophan and serotonin have not shown a similar effect.¹⁶ Moreover, uveal melanoma appear to express transmembrane receptors for melatonin. In a study performed by Roberts et al., melatonin and its membrane receptor agonists (MT1 and MT2) were found to inhibit the growth of uveal melanoma cells at low concentrations without impacting non-cancerous melanocytes.¹⁷

In animal studies, the effects of melatonin on uveal melanoma have varied. In a study performed on mice, the cell-line B16-F10 was injected in the tail vein of melatonin knockout mice which were then treated with melatonin 20 mg/kg. After 15 days, there were no significant differences in the number and size of lung metastases compared to controls.¹⁸ Another study performed on a human melanoma xenograft mouse model which were injected with DX3 melanoma cells while receiving injections of melatonin or melatonin analogues UCM 1033 and UCM 1037. When measuring tumor size both four weeks after treatment and after euthanization, the injections of UCM 1033 and UCM 1037 were found to inhibit tumor growth by 40 and 90 respectively, while melatonin provided no significant tumor growth suppression.¹⁹ Another study found that mice which received 5µg/g melatonin in their drinking water daily at the time of melanoma inoculation, had a lower size and weight of their melanoma compared to control groups 40 days after administration.²⁰ In a similar study, athymic mice were injected with melanoma cells and received either 5 µg/g body weight of melatonin in their drinking water together with 0.5% ethanol, 0.5% ethanol alone, or neither melatonin nor ethanol. After 40 days, the mice treated with melatonin had tumors lower in both size and weight.²⁰

A meta-analysis published in 2005 suggested that melatonin may have similar therapeutic effects in humans as well. Results found that melatonin treatment in patients with solid tumors was associated with a 44% reduction in the risk of death at one year.⁶ A clinical trial published in 1991 investigated the effects of melatonin treatment in 40 patients with advanced malignant melanoma, of which, 10 had uveal melanoma.⁷ Participants were given oral melatonin in doses ranging from 5 to 700 mg/m² four times a day. After a median follow-up time of 5 weeks, twelve patients showed a response or stable progression of disease. The response appeared to depend, however, on the dose, type of melanoma and metastasis location with a dose of 75 mg/m² having best effect with minimal side effects, primarily fatigue.⁷ Another clinical trial including five patients with metastatic melanoma studied the effect of adjuvant treatment with 50 mg melatonin taken orally. While four of the five patients had no response to the therapy, one patient continued taking melatonin for over 8 months and had almost total cancer regression.²¹ To date, there have been no earlier studies of the long-term effects of melatonin on human patients with uveal melanoma.

Methods

Trial Design

The study is an open randomized intervention study without a placebo control. 100 patients will be randomized to either treatment with melatonin 20 mg at 10 pm, or before bedtime, (melatonin group) or to standard follow-up (control group) for a period of 5 years. Aside from treatment with melatonin in the melatonin group, all participants will follow the same schedule for controls and follow-ups as other patients with uveal melanoma. Follow-up examinations are planned 1, 3, 6 and 12 months after primary tumor treatment with either surgery or brachytherapy, followed by annual or semi-annular examinations for life. Radiological examinations, usually with contrast-enhanced ultrasound or computed tomography, are performed every 6 months during the first five years. The population treated with melatonin will later be compared to the control group regarding the primary and secondary outcomes.

There are three reasons why we are not using a placebo in this study:

First, our most important outcomes are determined by the results of the radiological examinations (i.e., whether or not metastases are detected), which leaves little room for the placebo effect. Second, the standard clinical routine for uveal melanoma patients is not to use adjuvant treatments after the primary tumor treatment, but instead monitor patients with regular radiological follow-ups. This routine is followed internationally, with little variation between countries. Third, the risk of metastases and survival in the control group are already well known since it has remained consistent over the past several decades with little variation between different populations and time periods.^1,22−35 It is therefore relatively straightforward to compare our control group to previous cohorts that have not received placebo. Therefore, we will be able to confirm that our control group is representative of bigger populations. This comparison would be more difficult if the control group were to receive a placebo.

Study Objectives And Hypothesis

The primary objective for this trial is to investigate whether adjuvant treatment of non-metastatic uveal melanoma with melatonin 20 mg each night reduces the occurrence of metastasis 5 years after randomization. The outcome will be measured once the last person in the trial has taken their last melatonin tablet. The secondary objectives for the trial are to examine if adjuvant treatment with melatonin 20 mg each night for 5 years after randomization can:

1. Improve overall survival in 5 years?
2. Reduce the risk of developing another type of cancer in 5 years?
3. Improve overall survival after metastasis detection?
4. Examine if the occurrence of AE and SAE differs between the melatonin and control groups.

When the last recruited patient has been treated with melatonin for 3 years, interim analyses will be performed. At this point in time, we will compare the occurrence of metastases as well as the overall survival in the melatonin and the control group.

Our hypothesis, based on previous research, is that the group treated with melatonin will have a lower relative risk (RR) for metastasis 5 years after randomization.

Study Setting And Recruitment

Participants will be recruited to the trial from St. Erik Eye Hospital in Stockholm. The national management of uveal melanoma patients is centralized to this institution only. Similarly, the St. Erik Ophthalmic Pathology Laboratory receives most of the eyes with uveal melanoma that have been enucleated throughout the country, meaning that patients will be eligible for the trial regardless of where in Sweden they reside. If the patient is found to meet inclusion and exclusion criteria, they will be contacted via telephone and given information regarding the trial. If the potential participant is interested in taking part in the trial, they will be sent a written consent form and be contacted by a research team member via a service that allows for both video and audio contact, where the potential participant will be able to confirm their identity, ask any questions they may have regarding the trial, and receive additional information. If they wish to participate, they will be asked to sign the consent form (two copies) during the video-call and send one of the signed copies in a prepaid envelope to the research team. Once the signed consent form is received by the research team, the participant will be randomized to either the melatonin or the standard treatment group (control group).

Eligibility criteria

Inclusion criteria:

1. Participants must be 18 years or older
2. Participants must give written consent for participation in the trial
3. Participants must be clinically or histopathologically diagnosed with malignant melanoma originating from the choroid and/or the ciliary body
4. If the patient has already received treatment with melatonin for another reason, they have had a wash-out period where no melatonin was taken for a least two weeks prior to randomization 

 In addition to meeting these three criteria, at least one of the following criteria (5-11) must be met as well:

1. Participant’s tumor is categorized as a size of T3d or higher, corresponding to stage IIIB or higher (according to AJCC TNM version 8)³⁶
2. Participant’s tumor is of a size category “large” according to modified COMS-criteria (largest diameter >16 mm or largest height >8 mm)²²
3. Participant’s tumor is of a size category of T2a or higher prior to brachytherapy and has since regressed after brachytherapy³⁶
4. Participant’s tumor is composed of an epithelial cell type (>5 epithelial cells/hpf and >90 % epithelial cells in total)
5. Participant’s tumor has a low immunohistochemical expression of the protein BAP-1^37–41
6. Participant’s tumor has 9 or more mitoses per 40 hpf
7. Participant has via another published and validated prognostic test been found to have a risk of 60 % or higher for developing metastases after 5 years, for example, “Class 2 Gene Expression” or measurements of protein levels in the serum^3,42,43

Exclusion criteria: 

1. Participant is oversensitive to melatonin or any of the tablets’ contents. 
2. Participant has metastases detectable with radiological examinations or other methods at the time of recruitment (note that the development of metastases later on during the course of the trial does not disqualify a participant)
3. Participant is unable to provide consent
4. Participant has compromised liver function, for example due to liver cirrhosis or hepatitis
5. Participant is pregnant or wishes to become pregnant before the planned completion of melatonin treatment (women of child-bearing potential, WOCBP). Women admitted to the trial who become pregnant during the course of the trial before the trial’s completion will be withdrawn from the study
6. Participant is breastfeeding or wishes to breastfeed before the planned completion of melatonin treatment. Women admitted to the trial who begin breastfeeding during the course of the trial before the studies completion will be withdrawn from the study
7. Participant has epilepsy
8. Participant is treated, for more than 4 weeks, with CYP1A2-inhibitors Fluvoxamine, Quinolones, or Verapamil, Cimetidine, with combined hormonal contraception (containing ethinyl estradiol and progestogen), with hormonal substitution therapy, with 5-methoxypsoralen or 8-methoxypsoralen, or with cimetidine. If the participant, after being included in the trial, starts a lasting treatment (more than 4 weeks) with one of the previously mentioned substances, the participant does not need to cease participation in the trial but instead can refrain from taking melatonin during their treatment with these substances and then resume their melatonin treatment with the ordinary, daily dose of 20 mg at 10 pm. 
9. Participant was diagnosed with uveal melanoma more than 12 months prior to recruitment 

 Who will take informed consent?

A research member will obtain informed consent from the trial participants. In Sweden, informed consent must be collected by a licensed physician. The informed consent form will be sent to the participant via post which the participant will sign if they wish to participate in the trial and send it back to the research team who will also sign it and send a copy back to the participant. The participant will then be randomized to either melatonin group or to melatonin group. 

Interventions

Randomization And Allocation

The randomization takes place when the participant has sent their signed informed consent form to the research team, agreeing to be a part of this clinical trial. 50 sheets of paper labeled “melatonin” and 50 sheets of paper labeled “control” will be preserved in a total of 100 sealed, identical envelopes, mixed in one box. When the written informed consent is received from a participant, we will randomly choose one of these envelopes and open it. The content will then determine the randomization of the patient i.e., melatonin or control. When the process of randomization is complete, the participant will be informed of the outcome. If they have been randomized to the melatonin group, they will receive a prescription for melatonin and an order will be placed for 15 containers of melatonin tablets (corresponding to 1 year of consumption) each year during the 5-year period. The participating research staff as well as the participants will therefore be aware of their randomization outcome, either to treatment with melatonin or to composing the control group.

Blinding

This trial is not blinded.

 Intervention

Participants will be equally randomized into two groups: the melatonin group (treated with 20 mg melatonin each night for five years) or the control group (no intervention). When a patient is recruited and randomized to the melatonin group, blood samples will be ordered by a licensed physician regarding creatinine, electrolytes (Sodium, Potassium) and alanine transaminase (ALAT). This process will be repeated after 2 and 4 years. 

 Table 1. Study Design.

*= Primary treatment of uveal melanoma in the eye is either enucleation (surgical removal of the eye) or brachytherapy (local radiation therapy of the eye).

**=Evaluation of the proportion of subjects with metastases is performed through data collection via registries, chart documentation, and statistical work. It therefore does not require subjects’ active participation. 

A= Follow-ups at St. Erik Eye Hospital or at the participants local eye clinic. Examination of the eye, for subjects treated with radiation, or of the prosthesis and/or orbita, for subjects treated with enucleation. Follow-up interval +/- 4 weeks during the first year and +/-8 weeks after the first year.

B = Radiological examination of the liver with ultrasound or computer tomography every six months for the first five years after diagnosis; can be performed at the participant’s local healthcare clinic. Follow-up interval +/- 4 weeks during the first year and +/-8 weeks after the first year.

Table 2. Flow chart 

Data collection

A case report form (CRF) will be established in paper form and used for data collection, where subjects will be identified through a trial-specific number only. The examiner is responsible for assuring that registered information is correct and complete, and that the reporting is performed according to the predetermined timeline. The principal investigator will sign the completed CRF and a copy will be archived where the trial takes place.

Follow-up

The subjects will take their medication (tablets) at home and confirm that they have received each package of melatonin sent to them. They will, one month following recruitment, be contacted via telephone and asked about their compliance to the treatment. The participants will then continue to be contacted via telephone every six months throughout the trial period and asked questions about compliance, adverse events (AE) and serious adverse events (SAE). After the termination of the trial, the subjects will continue their yearly control visits at St. Erik Eye Hospital, or at their local ophthalmology clinic, for the remainder of their lives, as all uveal melanoma patients do.

In the event of detection of metastases

If a suspected metastasis is detected in radiological examinations and then verified with a biopsy, the patient will be referred by their physician to an oncology clinic in their home region. This is a standard clinical routine and will not be impacted by this trial. The oncology clinic will make a decision regarding next steps to investigate, examine and treat the metastases. Patients with metastases typically receive systemic chemotherapy, immunotherapy with so-called checkpoint inhibitors, and/or regional perfusion treatment of the liver where high doses of chemotherapy are injected into the liver's circulatory system. These treatments are demanding for patients and can result in side effects such as fatigue, susceptibility to infection, dry mucous membranes, and pain. The average survival following metastasis detection is about one year. Metastasis detection does not alter the melatonin doses or treatment instructions in this trial. Melatonin given at a dose of 20 mg at 10 pm has shown particularly positive effects in advanced stages of cancer in earlier studies.¹⁰

 It has also been reported that systemic chemotherapy is more easily tolerated in patients who are simultaneously treated with melatonin, particularly in regards to neurotoxicity, thrombocytopenia, weight loss, and asthenia.⁴⁴ Furthermore, there are fewer cases of alopecia (hair loss) and infection in patients taking 20 mg of melatonin at 10 pm while undergoing radiotherapy.⁴⁵ If participants in this trial take melatonin from the time that their metastases are detected, the metastases will be included in both the intention-to-treat as well as the per protocol analysis. Survival in the melatonin group following metastasis detection will therefore be counted in the patients still taking melatonin. 

Withdrawal

Subjects may voluntarily withdraw from the trial at any time without impacting further standard treatment. The principal investigator reserves the final right to terminate the trial for a specific subject due to unacceptable side effects or poor compliance. If a subject terminates their participation in this trial, their trial-specific ID will not be re-used. They will not be able to re-join the trial. No further data will be collected, however, data that has already been collected will be used for the final analysis of the trial. Participants who withdraw within 6 months following randomization will be replaced by newly recruited and randomized patients with a ratio of 1:1 i.e., if two participants withdraw from the trial within 6 months, they will be replaced by two new participants. Patients who withdraw from the trial after 6 months following randomization will not be replaced.

Sample Size

Our power calculations will be based on the following:

1. A previously calculated metastasis incidence of 60% five years following diagnosis for individuals not taking melatonin (participants in the control group). This is a relevant calculation considering the high-risk population recruited based on our inclusion criteria.^46–49

2. An earlier study which included study participants with surgically removed lymph node metastases of malignant melanoma which showed that 31% (5 of 16 participants) of those treated with 20 mg of evening melatonin developed distant metastases compared to 71% (10 of 14 participants) of those not treated with melatonin.⁸

Based on this previous research, the following assumptions are made:

1. The number of participants in the melatonin group which will have developed distant metastases after 5 years: 30%

2. The number of participants in the control group which will have developed distant metastases after 5 years: 60%.

3. Alpha: 0,05

4. Beta: 0,2

5. Power: 80%

6. Results: 42 participants must be included in each group, i.e., both the melatonin and the control group, in order to achieve statistical significance (Table 3). To obtain a safety margin in case some participants withdraw from the trial, we will strive after a group population of 50 participants per group.

Outcomes

The primary outcome is the number of patients which develop metastasis in the melatonin group vs. the control group. This will be evaluated as a relative risk (RR), measured as relative risk with a 95% confidence interval. The secondary outcomes include the following:

1. Number of patients developing metastasis in the melatonin group vs. the control group in 5 years, evaluated as Cox regression hazard ratio (HR), measured as hazard ratio with relevant covariants, with a 95% confidence interval.

2. The overall 5-year survival from randomization in the melatonin group vs. control group, evaluated with the Log-Rank test through Kaplan-Meier curve.

3. The overall 5-year survival from the detection of metastasis in the melatonin group vs. control group, evaluated with the Log-Rank test through Kaplan-Meier curve.

4. Number of patients which develop other types of cancer in the melatonin group vs. control group, evaluated as relative risk (RR), measured as relative risk with 95% confidence interval.

5. Number of patients developing other cancers in the melatonin group vs. control group, evaluated as Cox regression hazard ratio (HR), measured as hazard ration with relevant covariants, with 95% confidence interval.

6. Number of patients with AE and SAE in the melatonin group vs. control group, assessed by CTCAE and evaluated as relative risk (RR) with a 95% confidence interval.

Other outcome measures:

1. Interim analysis: number of patients developing metastasis within 3 years in the melatonin group vs. control group, evaluated as relative risk (RR), measured as relative risk with 95% confidence interval.

2. Interim analysis: overall survival in 3 years in the melatonin group vs. control group, evaluated with the Log-rank test.

End Of Study Definition

The trial will be terminated when the last participant in this trial has had their five-year control (Last Subject Last Visit - LSLV). No further treatment or contact with the participants will be made after this point of time.

Interim Analyses

Interim analysis will take place after two and three years during the trial.

Monitoring

In order to assure that the trial is performed according to the protocol - that the data is collected, documented and reported according to ICH-GCP as well as regarding ethical and regulatory requirements - the trial will be monitored by an independent monitor before the start of the trial, during the course of the trial, and after the trial ends, through Karolinska Trial Alliance. This will take place according to the monitoring plan for the trial and aims to ensure the rights, safety and well-being of participants as well as to oversee that data in the CRF forms is filled in correctly.

Safety And Adverse Events

Discussion

Melatonin is a hormone which positively impacts our immune system, inhibits angiogenesis, and stimulates apoptosis in malignant cells. This hormone may be a suitable candidate for an adjuvant treatment in uveal melanoma, particularly for patients with high risk for metastasis development but do not yet have detectable metastases at diagnosis.¹⁴

A dose of 20 mg per day or higher has been used in at least 14 earlier randomized clinical studies for patients that have been diagnosed with various forms of cancer.^{8–10,13,44,49,51−53 16–18, 21,30, 45–52, 54} In eight of these studies, the treatment has been used for at least a year in a total of 651 patients (30 + 356 + 49 + 14 + 12 + 55 + 35 + 100) in the melatonin group.^{8–10,13,44,49,51−53} In these clinical trials when the median patient had been treated with 20 mg melatonin per day for a year or longer, no blood samples or other tests were taken regarding subclinical AE, i.e. leucopenia, thrombocytopenia, hyperglycemia, hypokalemia, hyponatremia, hyperbilirubinemia, and proteinuria.^{8–10, 13,44,51} One exception is the clinical trial performed by Lissoni et al. where 100 patients with metastasized lung cancer were randomized to either systemic chemotherapy or systemic chemotherapy with melatonin. In this study, thrombocytopenia was evaluated, which was significantly lower in the melatonin group.⁴⁴ In another study, blood samples were taken to measure white blood cells and eosinophils during each cycle of IL-2 in patients with advanced gastrointestinal cancer treated with 50 mg of melatonin at 10 pm during one week per month as an adjuvant treatment.⁵²

Regarding toxicity and adverse events, these studies have in general reported few side effects of melatonin, such as mild anxiety, though subjects in another study experience decreased anxiety.^8,51 In most studies, no differences in side effect outcomes between melatonin and placebo groups were found regarding melatonin-related toxicity including nausea or other gastrointestinal issues.⁸ One study found no significant differences in Quality OF Life (QOL) QLQ-C30 or in side effect subcategories including physical, emotional, cognitive, social, fatigue, nausea, pain, insomnia, lack of appetite, obstipation or diarrea.⁹ No cardiovascular, pulmonal, renal, or hematological complications were observed when using melatonin as an adjuvant treatment to IL-2 in patients with advanced gastrointestinal cancer.⁵² To the contrary, some studies reported a better cytotoxic chemotherapy response regarding neurotoxicity, thrombocytopenia and asthenia in groups receiving melatonin as well as significantly fewer complications involving infections related to radiation therapy and/or steroid treatments.^44,51 Other studies found an improvement in the Karnofsky Performance Scale in the melatonin group.^52,53

The toxicity of melatonin has been low in earlier animal and human studies. In animals, an LD50 (lethal dose in 50% of experimental animals) could not be established since no doses, to date, have been proven to be lethal. The highest used daily dose known for the sponsor is 800 mg/kg body weight in mice (corresponding to 60 g for a 75 kg body weight). A higher dose could not be attained since higher doses were not water soluble.⁵⁴ In one study, 5 patients with hyperpigmented skin who received 1 g melatonin /day for 25–30 days were observed to have slightly lower levels of growth hormone, luteinizing hormone, follicle stimulating hormone and cortisol during treatment. However, there were no changes in their hematological status (white blood cells, hemoglobin, hematocrit, thrombocytes, reticulocytes and differential white blood cells count), plasma creatinine, uric acid, calcium, phosphate, transaminases, LDH, bilirubin, total protein, albumin, thyroxin or of retinal appearance.⁵⁵ In a study performed on 11 patients with Parkinson’s disease that received 50–100 mg melatonin daily, no changes in serotonin levels in urine was observed. At least one other previous study has had participants take 20 mg of melatonin every evening for five years.⁵⁶ In this study, patients with metastasized non-small cell lung cancer were randomized to treatment with either cisplatin and etoposide or to cisplatin, etoposide and melatonin. The patients who received melatonin were found to have both significantly better overall survival and significantly fewer reported side effects.⁵⁶

Animal studies indicate that melatonin can downregulate the pituitary-gonadal axis, which may result in hypogonadism or delayed puberty.​​^55,57 Treatment with low doses (2 mg) of melatonin in men did not, however, change blood levels of testosterone or luteinizing hormone.⁵⁸ Treatment with melatonin in women has been shown to lower the secretion of gonadotropin in a rapport from a clinical phase II-study where 1400 women were treated with 75 mg melatonin each evening for four years, though no other side effects were observed.⁵⁹ Considering these findings, prepubescent children and women of reproductive age will be excluded from this trial.

Even if melatonin has shown potential as an adjuvant treatment of cancer including uveal melanoma, the timing of melatonin consumption is relevant as it is a hormone which is naturally secreted at 10 pm in the absence of light.⁶⁰ Melatonin given at the wrong time point in the circadian rhythm might have the opposite effect.¹⁴ Melatonin injections given in the morning have been shown to stimulate the growth of fibrosarcoma and Erlich tumors, while injections at 10 pm inhibit tumor growth.⁶¹ Furthermore, melatonin distribution several at multiple occasions during both day and night was found to exacerbate depressive symptoms.⁶² In a study performed on rats, treatment with peritoneal injections of 100 µg melatonin/day (corresponding to 30 mg/day given to an adult) were found to have more photoreceptor damage in the retina after illumination with high intensity fluorescence light of 1600 lux for 24 hours, compared to animals treated with placebo.⁶³ Therefore, as melatonin is a hormone important to our natural circadian rhythm, it is important to consider the timing of melatonin consumption, ideally at 10 pm.

If melatonin is found to prevent the development of metastases, there would be benefits for both the trial participants who took melatonin during the trial and for patients diagnosed with uveal melanoma in the future. By sharing our results in research articles or by other means, this benefit could become available to patients beyond Sweden’s borders as well. Melatonin is relatively accessible worldwide and could potentially reduce mortality for a large proportion of the 7000 patients diagnosed with the disease annually around the globe. We therefore believe that the benefits of this trial outweigh the limited potential risks.

Since data regarding the effects of melatonin as an adjuvant treatment in uveal melanoma is limited, this future clinical trial will be performed to investigate if adjuvant treatment with melatonin following diagnosis of the primary tumor, decreases the risk of developing macrometastases of uveal melanoma.

Abbreviations

AE: Adverse event

CRF: Case report form

CTIS: Clinical trial information system

CTR: Clinical trial regulation

GCP: Good clinical practice

ICH:  International Council for Harmonization

ITT:  Intention-to-treat

PP:  Per protocol analysis

SAE:  Serious adverse event /Serious adverse reaction

SUSAR:  Suspected unexpected serious adverse reaction 

Declarations

Acknowledgements

We would like to acknowledge Heléne Sjöö, a clinical trial official and educator at Karolinska Trial Alliance, for her guidance and support in formatting our study protocol and case report form. 

 Authors’ contributions

GS is the principal investigator; he conceived the study, drafted the proposal and led the development of the study protocol. RKO and AH are members of the research team and contributed to the development of the case report form and study protocol. All authors have read and approved the final manuscript.

 Funding

The authors of this paper have received funding from the following sources:

St. Erik Eye Hospital

The Swedish Society of Medicine (SLS-971390)

The Royal Swedish Academy of Sciences (ME2019-0036)

The Swedish Cancer Society (20 0798 Fk)

Region Stockholm (RS-2019-1138)

The Swedish Eye Foundation (2022-05-02) 

Karolinska Institutet (FS-2021-0010)

 Availability of data and material

All investigators as well as the monitoring organization will have access to the final trial dataset. There are no contractual agreements that limit such access for investigators. The collection of personal information including but not limited to names, addresses, social security numbers, and other contact details about the trial's participants, and disclosure of such information to any party, is regulated by the The Swedish Medical Products Agency and subject to approval from the Swedish Ethical Review Authority.

 Ethics approval and consent to participate

The trial is going to be performed according to the trial protocol, CTR regarding human medicine (536/2014), Helsinki declaration, ICH-GCP, and the current national regulation relevant to this clinical trial. EU-trial number: 2022-500307-49-00. The trial is approved by The Swedish Medical Products Agency and The Swedish Ethical Review Authority. 

 Signed informed consent forms will be obtained from all trial participants (see methods section for more information).

 Consent for publication

Not applicable.

 Competing interests

The authors declare that they have no competing interests.

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