Clinical characteristics and prognosis of 40 patients with periorbital metastasis of neuroblastoma

Background This study was performed to summarize the clinical characteristics of patients with periorbital metastasis of neuroblastoma (NB) and analyze the short-term prognosis. Methods This study included 40 patients with periorbital metastasis of NB from March 2007 to March 2018. The patients’ clinical characteristics and short-term prognosis were retrospectively analyzed.

Background Neuroblastoma (NB) is one of the most common pediatric extracranial solid tumors [1] and has a high rate of malignancy. Most patients have distant metastases at the time of the initial diagnosis. These metastases are most frequently observed in the bone and bone marrow [2,3] , and periorbital soft tissue involvement is more common than in other nonperiorbital tumors. Harreld [4] reported that 30% of pediatric patients with NB developed periorbital metastasis over an 18-month period. In the present study, we collected the

Patients
The medical records of patients who were diagnosed with high-risk NB and periorbital metastasis were reviewed. The data collected included sex, age, clinical manifestations, laboratory examination findings (including the concentrations of lactate dehydrogenase [LDH], neuron-specific enolase [NSE], and vanillylmandelic acid [VMA]), N-myc, and chromosome status. Periorbital metastasis was defined as involvement of one or more of the following structures: periorbital bone (ethmoid bone, frontal bone, lacrimal bone, palatal bone, maxilla, sphenoid bone, or zygomatic bone), soft tissue around the orbit, or eyeballs and their auxiliary structures (lacrimal glands, vessels, nerves, intraorbital soft tissue, and eyelid). Each patient with NB was staged according to the International Neuroblastoma Staging System and assigned a risk group according to the International Neuroblastoma Risk Group and the Children's Oncology Group [5,6] .

Treatment
The BCH-HR-NB-2007 protocol was used in all patients and included the following four main components, which lasted about 18 months: (1) induction chemotherapy, (2) local control, (3) consolidation, and (4) maintenance therapy with isotretinoin (13-cis-retinoic acid). Local control treatment included surgical resection, generally after four to six cycles of induction chemotherapy, and external beam radiation to the primary site and other sites of active residual disease. Consolidation therapy included myeloablative chemotherapy, autologous stem cell rescue, and radiation therapy.

Tumor response criteria
The treatment response was evaluated using the International Response Criteria for NB.
Briefly, a complete response was defined as no identifiable tumor with a normal catecholamine level. A very good partial response was defined as a reduction of the primary tumor by 90 to 99% with a normal catecholamine level with or without residual 99Tc bone changes. A partial response was defined as a reduction of the primary and metastatic tumors by > 50%. A mixed response was defined as a reduction of any measurable lesion by > 50% with a reduction of any other lesion by < 50%. Stable disease was defined as no new lesion and an increase in any existing lesion by < 25%. Progressive disease was defined as any new lesion or an increase of any measurable lesion by > 25%.

Statistical methods
Event-free survival (EFS) was calculated from the date of diagnosis until the date of relapse, progression, secondary malignancy, or death, whichever occurred first. Overall survival (OS) was calculated from the date of diagnosis until death of any cause. Survival rates and standard errors were estimated using the Kaplan-Meier method. Differences in survival rates between the two groups were compared using the log-rank test. P-values of < 0.05 were considered statistically significant.

General information
A total of 47 patients who were diagnosed with high-risk NB met the study inclusion criteria, but 7 patients discontinued treatment or were transferred to other hospitals. Therefore, 40 patients were involved in the final study and followed up. Their median age at onset was 30.5 months (range, 8-132 months), and their median disease course was 1.5 months (range, 6 days to 8 months). The clinical data of these 40 patients are shown in Table 1. intraorbital soft tissue metastasis was present in 30, one or more metastases to the eyeballs with involvement of one or more eyeball auxiliary structures were present in 14 patients, and involvement of one or more sinus cavities near the orbit was present in 14 patients (Table 2).

MYCN gene and chromosome
At the initial diagnosis, 38 patients underwent MYCN gene detection and 17 (44.7%) had MYCN amplification. Fourteen patients underwent chromosome G banding detection; among these patients, 4 had a normal karyotype and 10 had chromosomal abnormalities.
The structural chromosomal abnormalities mainly involved 1p, 3p, and 1q, and the chromosome number abnormalities mainly involved deletion of chromosomes 11, 21, and 10 and gain of chromosomes 6 and 2. Table 3 lists the patients' characteristics. At the initial diagnosis, the median LDH concentration was 1095 U/L (range, 366-7799 U/L), and the LDH concentration was > 1500 U/L in 35% of the patients. No significant difference was found between the patients with an LDH concentration of > 1500 or < 1500 U/L according to 5-

Discussion
NB is an embryonal tumor that originates from neural crest cells and accounts for 7-8% of all pediatric tumors and 15% of deaths caused by pediatric malignancies [7] . The peak age of NB is 2 to 4 years, and > 80% of children are diagnosed at > 5 years of age [8] . The median age of the 40 patients in our study was 30.5 months, and only 1 patient was older than 10 years; this is similar to previous studies.
As reported by Kieuhoa [9] , the primary tumor site was in the posterior mediastinum in about 15% of patients with NB, and this site was associated with a better prognosis. In our study, the primary tumor site was in the posterior mediastinum in only 5% of patients, Approximately 60% of NB can reportedly metastasize to the bone, bone marrow, lymph nodes, and liver. Among these sites, bone marrow and bone metastases are most frequently observed (about 70.5% and 55.7% of cases, respectively), and all sites are strongly associated with a poor prognosis [10] . In the present study, all patients had three or more sites of metastasis. Periorbital metastasis is one component of multiple metastases throughout the body. All patients in this study had bone and bone marrow metastasis. Based on the above findings, infiltration of local soft tissue through bone marrow and bone metastasis is believed to be a route of tumor cell metastasis to the head and facial soft tissue. Harreld [4] reported that 30% of children with NB older than 18 months with distant metastasis had periorbital bone and soft tissue metastasis; among them, children with manifestations of soft tissue metastasis such as periorbital bruising had a worse prognosis. Children with central nervous system and intracranial metastases of NB also had a poor prognosis, showing a high mortality rate. Single-center data from another study showed that among patients with NB, about 1.9% had central nervous system metastasis and 14.0% had intracranial metastasis [11] . In the present study, about 22.5% of patients had central nervous system metastasis (including brain parenchymal and spinal metastasis), and the rate of intracranial metastasis was as high as 60%.
Therefore, the high rate of intracranial metastasis was another factor related to the poor prognosis in this study.
In recent years, research has showed that the MYCN gene is an indicator of NB with aggressive progression and a poor prognosis [12,13] . Wang [14] reported that 12% of children with NB had MYCN amplification. The MYCN amplification rate of the patients treated in our center during the same period was 16.0% [15] , while the rate in our study cohort was 44.7%. Therefore, the children in our study showed an extremely poor prognosis. We found no significant difference in the survival rate between the children with and without MYCN amplification in this study, which was probably due to the concurrence of multiple poor prognostic factors including the high rate of bone and marrow metastasis, high rate of intracranial metastasis, and high serum levels of tumor factors, resulting an overall poor prognosis. Many tumor suppressor genes are present in chromosome 1p, and changes in the regulatory sequence or coding of the gene or complete deletion of the gene will lead to loss of the cell's anti-cancer effect, which will also lead to the progression of tumor cells [16] . Some investigations have suggested that chromosomal structural abnormalities in the 1p and 17q regions are closely related to the MYCN gene status [17] .
LDH is an enzyme that plays an important role in glycolysis and can be used as an indicator of the systemic tumor burden. NSE is also an enzyme takes part in the glycolysis process; it exists in neurons and nerve-derived cells and is a highly specific and sensitive indicator of NB [18] . An LDH concentration of > 1000 U/L and NSE concentration of > 100 ng/ml are poor prognostic factors [19] . In the present study, 35% of children had an LDH concentration of > 1500 U/L, while 57.5% of children had an NSE concentration of > 370 ng/ml (detection maximum), indicating a poor prognosis. NB originates from neural crest or primitive nerve cells that synthesize and secrete catecholamines. The catecholamine metabolite VMA in urine is a specific tumor index that can be used as an important diagnostic clue [20] . In the initial stage, all children in the present study exhibited an increased level of urine VMA. Thus, the children with orbital metastasis of NB had a large tumor load and adverse factors resulting in a poor prognosis.
In this study, 40 children were treated, evaluated, and followed up based on the BCH-NB-2007-HR protocol. Other single-center analyses showed that the 5-year EFS of NB was 64.3% [21] and the 5-year EFS of NB with bone marrow metastasis was 36.1% [22] ; in the present study, however, the 5-year EFS of NB with periorbital metastasis was only 6% and the 5-year OS was only 16%. Therefore, NB with periorbital metastasis is characterized by aggressive progression, early death after progression, a low retreatment response rate, Availability of data and materials: On an aggregated level, the BCH hematology-oncology center may share aggregated data upon reasonable request. The manual for the intervention is free to use for any other research team after information and education from the BCH hematology-oncology center research team.
Competing interests: The authors declare that they have no competing interests.