Gynecological brachytherapy for postoperative endometrial cancer: dosimetric analysis (Ir-192 vs Co-60)

Endovaginal brachytherapy treatment dosimetry differences were studied using Ir-192 or Co-60 sources for postoperative endometrial cancer.

A prospective descriptive study was conducted. Thirty-six dosimetry plans of different patients were studied (15 by Ir-192 and 21 by Co-60). Variables studied included D2cc Rectum, D2cc Bladder, D2cc Sigmoid, dose percentage at point 0 (applicator surface on the top of the cylinder) and dose percentage at point 1 (5 mm deep on the top of the cylinder). A comparative analysis was performed of the values obtained from each variable between Ir-192 and Co-60 treatments. We compared average of each variables between Iridium and Cobalt by T Student for independent samples (SPSS 22).

There were no significant differences on using Ir-192 or Co-60 by variables, except for dose percentage at point 1 in which we detected significant differences (Table 1). Table 1 The results Variables Sources Iridium 192 Cobalt 60 D2cc Rectum (mean dose) [rank] 6.01 Gy [3.99-7.90] 5.28 Gy [3.87-6,34] D2cc Bladder (mean dose) [rank] 5.82 Gy [4.20-8.38] 5.05 Gy [2.23-6.95] D2cc Sigmoid (mean dose) [rank] 4.43 Gy [1.66-6.67] 2.33 Gy [0.60-4.28] Dose percentage at point 0^a (mean) [rank] 210.74% [120.90-234.90] 204.75% [177.10-223] Dose percentage at point 1^b (mean) [rank] 93.49% [87.30-100.60] 100.11% [96.70-102] ^aPoint 0: point to the applicator surface ^bPoint 1: point to 5 mm applicator surface DISCUSSION: Brachytherapy treatment dosimetry plans are similar using Ir-192 or Co-60, except dose percentage at point 1. In the scientific literature, some differences exist and there are some advantages in using cobalt.