gms | German Medical Science

Background: The aim of this prospective phase-III-study was to evaluate, whether sodium selenite is able to compensate a preexisting selenium deficiency and to prevent radiation induced diarrhoea in adjuvant radiotherapy (RT) for pelvic gynecologic malignancies.

Methods: 80 patients with uterine squamous cell (n=14) or adenocarcinoma (n=66) after curative surgical treatment and a selenium deficiency (whole blood) were randomized before radiation therapy. In the supplementation group patients received 500 µg sodium selenite per os on the days of radiotherapy and 300 µg sodium selenite on the days without treatment till the last day of radiotherapy. In the control group adjuvant radiotherapy was given without supplementation of selenium. During treatment levels of whole blood selenium were measured after completing 50% of RT and at the end of RT using spectrofluorometer with a normal range of 85-162 µg/l [Winnefeld et al. 1995]. Radiotherapy was delivered with a linear accelerator, total doses ranged between 45 and 50 Gy. Radiation-associated diarrhoea was recorded weekly according to the CTC-criteria. Statistical analysis was performed using t- and u-test, overall survival were analysed as time-event curves by Kaplan-Meier method including log-rank test. The study was approved by the international ethical commission Freiburg, Germany.

Results: 73 patients with a median age of 65 years (range 31-80) were evaluable. Of these 73 patients 37 were in the supplementation group and 36 in the control group. Before adjuvant radiotherapy (RT), in the supplementation group the mean whole blood selenium level was 65.1 µg/l and in the control group 62.6 µg/l. At the end of RT there is a significant increase of the mean level of whole blood selenium in the supplementation group (89.3 µg/l). In the control group no change of mean selenium levels was observed (61.1 µg/l) (t-test, p=0.0001). There has been a statistically significant difference between the study groups towards a lower incidence of diarrhoea CTC 1/2 in week 5 with selenium supplementation (u-test, p=0.038). With a median follow up of 24 months (12-54) the actuarial 4 year overall survival rate of patients with supplementation of selenium was 95.5% comparing to the control group with 85.3% (p=0.3446).

Conclusion: Our data suggest, that supplementation of sodium selenite is able to significantly increase whole blood selenium levels in patients with gynecological tumours undergoing radiotherapy of the pelvic region. Concerning radiation-induced diarrhoea we investigated a significant trend for prevention in the supplementation group so far. Overall survival rates show that supplementation of selenium does not interfere with the biologic effects of ionizing radiation. The presented study continues and within the next two years 50 patients in both groups should be enrolled.