Women with high-risk endometrial cancer (EC) are at an increased risk of metastasis and death. The randomized, intergroup PORTEC-3 study assessed the benefit of adjuvant chemotherapy during and after radiotherapy (RT) versus pelvic RT alone in this patient population. The researchers presented the study at the ASCO Annual Meeting.

A total of 660 women with high-risk EC (defined as Federation of Gynecology and Obstetrics stage I, grade 3 with deep myometrial invasion and/or lymphovascular space invasion; stage II or III; or serous/clear cell histology) were randomized 1:1 based on participating center, lymphadenectomy, stage, and histologic type to receive RT alone (48.6 Gy in 1.8 Gy fractions; n = 330) or chemotherapy plus RT (two cycles of cisplatin 50 mg/m² in week 1 and four cycles of RT, followed by four cycles of carboplatin area under the curve = 5 and paclitaxel 175 mg/m² at three-week intervals; n = 330). Patients were enrolled between 2006 and 2013, for a median follow-up of 60.2 months (range = 47.1–72.9).

Three-year overall survival ([OS], a co-primary endpoint) was 84.4% for those treated with chemotherapy and RT compared to 83.9% for those treated with RT alone, whereas five-year OS was 81.8% and 76.7%, respectively (overall hazard ratio [HR] = 0.79; 95% CI, 0.57–1.12; p = 0.183).

Three-year failure-free survival ([FFS], a co-primary endpoint) was 79.7% for those treated with chemotherapy and RT compared to 71.8% for those treated with RT alone, whereas five-year FFS was 75.5% and 68.9%, respectively (overall HR = 0.77; 95% CI = 0.58–1.03; p = 0.078).

Patients with stage III EC had lower five-year FFS (63.9% versus 78.9%; p < 0.001) and OS (74.3% versus 83.1%; p = 0.003) compared to those with stage I or II. Patients with stage III disease also had the greatest benefit of chemotherapy plus RT: five-year FFS was 69.3% compared to 58.0% for RT alone (95% CI = 0.45–0.97, p = 0.032), and five-year OS for 78.7% versus 69.8%, respectively (p = 0.114).

“Adjuvant chemotherapy given during and after pelvic RT for treatment of high-risk EC did not significantly improve five-year FFS and OS compared with RT alone,” the authors concluded. “For women with stage III EC, FFS was, however, significantly improved with chemotherapy plus RT by 11% at five years.”

The researchers are continuing long-term follow-up of this study.