Radiation in thyroid cancer
In 2020, new cases of thyroid cancer are estimated to be 52,890 patients with a 2.9% death rate ("SEER Cancer Stat Facts: Thyroid Cancer. National Cancer Institute," 2021). Thyroid cancer is more common in young and middle-aged women. Its one of the most common cancers in humans and papillary and follicular types are its most prevalent types (Petrich et al., 2001).
Surgery, radiation therapy, and chemotherapy are the main treatments for thyroid carcinoma (Petrich et al., 2001). Radiation with ionizing rays has negative impacts on biological tissues, and in certain doses, quantities and intensities can cause irreversible tissue damages, cancer, and even death (Mehrosadat et al., 2015). Despite its negative results, radioactive iodine has been used to treat benign and malignant thyroid cancer since 1940 (Siegel, Naishadham, & Jemal, 2012). Thyroid cancer can be surgically removed after diagnosis and since its remaining cells absorb radioactive iodine, they are eliminated by radioactive iodine after surgery. Beta particles radiating from radioactive iodine destroy the follicular cells and gradually lead to a decrease in remaining thyroid volume and control of thyrotoxicosis. As a result, iodine therapy is usually performed to destroy the remaining cancerous cells of the thyroid or probable cancer metastasis. An important feature of thyroid cancer cells that differs from other cancer cells is that they considerably absorb iodine, and as a result, the iodine is concentrated in the thyroid remaining cells, which results in cell death. It must be said that most healthy cells of the human body survive as they do not absorb iodine (Petrich et al., 2001). Radiation therapy is performed with radioactive iodine or by external radiation. After thyroidectomy, it must be ensured that no cancer cells are left. In contrast to most cancers, in which chemotherapy is used for the elimination of remaining cells, chemotherapy is not effective for thyroid metastases and thereby these patients are treated with radioactive iodine. It is obvious that iodine therapy maximizes the therapeutic effect of subsequent treatments and it also reduces the recurrence and mortality rates of thyroid carcinoma and even can prevent distant metastasis (Haugen et al., 2016). When radioactive iodine is absorbed by thyroid tissue, its therapeutic effects begin; because of high-energy beta ray emission and eventually will result in cell death within a few weeks (La Perle et al., 2013).
Iodine 131 is one of the radionuclides which accumulate in the thyroid gland. In patients who underwent thyroidectomy, as the thyroid gland has been removed, iodine 131 is distributed to other organs of the body. Iodine 131 or radioactive iodine is a radiant isotope of iodine that has a half-life of 8 days. This isotope is mainly produced artificially and it is often used in imaging procedures or the treatment of hyperthyroidism, thyroid cancer, and some other cancers. In imaging studies such as thyroid scans, the patient receives a small dose of radioactive iodine that accumulates in thyroid tissue or certain types of tumors, and sites of radioactive iodine accumulation can be detected using a scanner. It has been reported that locations, where more radioactive iodine has accumulated, are overactive sites (hot thyroid nodules) (Aschebrook-Kilfoy et al., 2013; Schneider & Chen, 2013).
Senna
Herbal Medicine has been used widely in traditional and ethnic medicine(Ardekani, Askari, & Mohagheghzadeh, 2020). In recent years most of researchers in field of herbal medicine have put an emphasis on clinical trials of such products(Amiri-Ardekani & Tehrany, 2021; Bhosale & Banerjee, 2020). One of these valuable herbs is Senna. Senna (Senna alexandrina Mill.) from Genus Senna and Leguminosae family("The Plant List," 2021) is a valuable plant due to its laxative(Vilanova-Sanchez et al., 2018; Wang et al., 2020), anti-obesity, anti diabetic(Yuniarto, Sukandar, Fidrianny, Setiawan, & Ketut, 2018), and hepatoprotective(Wang et al., 2020) activity. S.alexandrina is one of the most popular and important species of this genus, which is mentioned in the world's renowned pharmacopeias(Ahmad, Hassan, Abbasi, & Rehman, 2018). Many species of the Senna genus are sources of tannins, and thereby they have also high economic and therapetic value (Maia, Trevisan, Silva, Breuer, & Owen, 2017; Oladeji, Adelowo, & Oluyori, 2021).
sennosides are among the major ingredients of Senna. These glycosides (especially A and B sennosides and their active metabolite, rhein-anthrone) are responsible for Senna leaves and fruit laxative activity. Two mechanisms have been proposed for Senna laxative activity. The first mechanism is electrolyte and water absorption from the large intestine that results in higher volume and pressure in the large intestine and eventually increases colon motility. The second mechanism is active chloride secretion mediated by stimulation of endogenous prostaglandin E2 that results in increased water and electrolyte content of the intestine and eventually increased colon motility(Ramchander & Middha, 2017; Zhao et al., 2016).
Due to the safety and therapeutic aspects of S.alexandrina from one hand and the need to increase radiation dose excreted at discharge time in patients who underwent iodine therapy for the first time in the world in this study we evaluate the role of Senna tablets (commercially known as C-Lax®) in increasing radiation dose excreted at discharge time in patients who underwent iodine therapy.