Preliminary analysis of RTOG 9708: adjuvant postoperative radiotherapy combined with cisplatin/paclitaxel chemotherapy after surgery for patients with high-risk endometrial cancer

Abstract

Purpose Patients with completely resected high-risk endometrial cancer have a risk of disease recurrence even with the addition of adjuvant pelvic radiotherapy (RT). A Phase II study was completed by the Radiation Therapy Oncology Group to assess the safety and toxicity of chemotherapy when combined with pelvic RT for these patients. Methods and materials Eligibility requirements included a total abdominal hysterectomy and bilateral salpingo-oophorectomy with Grade 2 or 3 endometrial adenocarcinoma with >50% myometrial invasion, stromal invasion of the cervix, or pelvic-confined extrauterine disease. This study was designed to administer 4500 cGy in 25 fractions to the pelvis, along with cisplatin (50 mg/m 2) on Days 1 and 28. Vaginal brachytherapy with a low-dose-rate applicator (1 × 20 Gy to the surface) or high-dose-rate applicator (3 × 6 Gy to the surface) was performed after external beam RT. Four courses of cisplatin (50 mg/m 2) and paclitaxel (175 mg/m 2) were given at 4-week intervals after RT completion. Results Forty-six patients were entered between October 1997 and April 1999. Two patients were ineligible (one with previous bladder cancer and one who had undergone surgery >8 weeks before the start of RT). Follow-up ranged from 6.9 to 48.8 months (median, 28.7 months). The disease was Stage III, II, and I in 66%, 16%, and 18% of patients, respectively. Two patients were not assessable because of incomplete treatment data. The protocol completion rate was 98% (41 of 42 assessable patients). Acute toxicity during RT/chemotherapy was Grade 1 in 27%, Grade 2 in 43%, Grade 3 in 27%, and Grade 4 in 2%. During adjuvant chemotherapy, the toxicity was Grade 1 in 7%, Grade 2 in 7%, Grade 3 in 21%, and Grade 4 in 62%. Severe toxicity was primarily hematologic. Chronic toxicity was Grade 1 in 20%, Grade 2 in 39%, Grade 3 in 16%, and Grade 4 in 2%, including 1 patient with a Grade 4 small bowel complication. At 24 months, the pelvic recurrence, regional recurrence, distant recurrence, disease-free survival, and overall survival rate was 2%, 3%, 17%, 83%, and 90%, respectively. Conclusion This treatment protocol demonstrated an excellent treatment completion rate and expected toxicity. Longer follow-up is needed to assess the outcome. To assess the efficacy of this adjuvant treatment program, a Phase III trial (Radiation Therapy Oncology Group 9905) was designed with high-risk uterine-confined disease to be randomized between pelvic RT alone and pelvic RT with chemotherapy.