THE VITAMIN E LEVELS DURING PROSTATE CANCER RADIOTHERAPY

Introduction: World Cancer Research Fund International points out prostate cancer as the second most frequent cancer in men worldwide. Radiotherapy is an important curative treatment modality in the management of prostate cancer. However, its use has many undesirable side effects associated with cellular oxidative processes. These side effects related to radiotherapy treatment appear because of the reactive oxygen species in the intracellular environment, which stimulates the formation of pro-apoptotic signal molecules. These molecules, in its turn, activate the p53 pathway, triggering a mitochondrial apoptotic cascade, leading to intracellular oxidative stress. A mechanism of cellular protection is the use of antioxidant agents to ensure their survival, reducing the amount and intensity of normal cell damage. Vitamin E is an important antioxidant, with a great potential to protect the organism against damages caused by radiotherapy treatment. Knowledge of serum antioxidant levels during radiotherapy, such as vitamin E, can offer benefits such as reducing the amount and intensity of adverse effects and reducing as well the toxicity of the method. Objective To evaluate vitamin E serum levels in patients undergoing radiotherapy for prostate cancer treatment. Methods: Longitudinal retrospective study of patients with prostate cancer submitted to external beam radiotherapy. The blood levels of vitamin E were checked before starting radiotherapy, and within 20 to 40 days after the end of treatment. Risk groups are in line with the NCCN classification. Results: Thirty-five patients with an average age of 67.6 years (55-79 / CI95% 65,9-69,3 / SD ± 4,9) were evaluated. According to risk group classification, 4 patients were low risk (11,4%), 23 patients were at intermediate risk (65,8%), and 8 were high-risk patients (22,8%). Patients received an external radiation dose of 70 Gy divided into 28 fractions (moderate hypofractionation). The pre-radiotherapy serum vitamin E average was 1,17 mg/dL (0,5-5,0 / CI95% 0,8-1,5 / SD ± 0,6) and the average after radiotherapy was 0,57 mg/dL (0,06-1,35 / CI95% 0,45-0,69 / SD ± 0,35), with statistically significant difference (p < 0,0001). Conclusion: A vitamin E deficit after radiotherapy was observed. This highlights the need to monitor serum levels throughout radiotherapy treatment to minimize some of its deleterious side effects.