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

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 x 20 Gy to the surface) or high-dose-rate applicator (3 x 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.