Late reactions after postoperative high-dose-rate intravaginal brachytherapy for endometrial cancer: a comparison of standardized and individualized target volumes

Abstract

Purpose: To compare retrospectively two treatment protocols for postoperative intravaginal brachytherapy as to frequency of late radiation reactions and vaginal recurrence of disease. Methods and Materials: Two hundred seventeen patients with Stage I–II endometrial carcinoma underwent total abdominal hysterectomy and bilateral salpingo-oophorectomy, followed by high-dose-rate (HDR) intracavitary irradiation, 5.5 Gy × 4 (22 Gy), to the upper 5 cm of the vagina. From 1988 to August 1991, the reference isodose was at 5 mm from the mucosal surface (standard treatment, 96 pts). From September 1991 to June 1996, the reference isodoses were chosen at 3 mm, 4 mm, or 5 mm depth depending on a clinical estimation of the mucosal thickness (individualized treatment, 121 pts). Maximum bladder and rectum doses were calculated from orthogonal X-ray films. Results: The patients were followed for 3 to 10 years. The rate of late vaginal reactions Grade 1 and 2 were 26% and 8%, respectively, after standard treatment, vs. 17% and 1% after individualized treatment ( p = 0.005). Bladder reaction rates were 9% Grade 1 and 1% Grade 2 after standard treatment vs. 1% Grade 1 after individualized treatment ( p = 0.005). Rectum reactions Grade 1 were seen in 5% and 1%, respectively. No Grade 3 reactions were observed. The reactions appeared after a median time interval of 9 months and 11 months, respectively. The rate of vaginal reactions was strongly correlated to the dose on the surface of the vaginal applicator, and the bladder reaction rate correlated with the calculated maximum bladder dose. Local vaginal recurrences were seen in 1 patient (1.0%) in the standard treatment group and in 3 patients (2.5%) in the individualized treatment group ( p = 0.78). Conclusions: By individualizing the depth of the reference dose in the vaginal mucosa according to its thickness and avoiding applicators with small diameters, the rate of reactions can be reduced without any significant increase in vaginal recurrences.