The PORTEC trial tested the role of postoperative pelvic radiation therapy for presumed stage I endometrial cancer in 714 patients. Eligibility criteria were stage IB, grades 1 to 2, and stage IA, grades 2 to 3; patients with stage IA, grade 3, were only 10% of the study population, and lymph node biopsies and peritoneal cytology were not required. Local-regional recurrences developed in 14% of the surgery group, compared with 4% of the postoperative pelvic radiation group. Overall, the 5-year survival rate was no different between the two groups (85% vs. 81%, respectively) (135). These results were confirmed by GOG99, a prospective, randomized investigation of surgery alone (including lymphadenectomy to the level of the inferior mesentery artery in some patients) versus surgery plus adjuvant pelvic radiation in intermediate-risk endometrial cancer (stages IA to IIb occult). Of 392 patients accrued to the study, more than 80% were actually low-risk patients (90.6% stage I, 81.6% grades 1 to 2, 82% <50% myometrial invasion). Disease recurrence was reduced by 58% (p = 0.007) with the use of postoperative pelvic radiation. After 2 years, the cumulative recurrence rate was 12% in the group with no postoperative treatment compared with 3% in the group that received pelvic radiation. The pelvic failure rate was 8.9% in the surgery-alone group compared with 1.6% in the postoperative pelvic radiation group. Overall survival rates were not significantly improved in patients receiving postoperative pelvic radiation compared with those treated only with surgery (92% vs. 86%, respectively) (279). Recently, the intergroup ASTEC/EN.5 trial provided further confirmation that external-beam radiation therapy in patients at intermediate to high risk of recurrence has no significant effect on overall survival (294).
Postoperative whole-pelvis external-beam radiation usually involves the delivery of 4,500 to 5,040 cGy in 180 cGy daily fractions over 5 to 6 weeks to a field encompassing the upper one-half of the vagina inferiorly, the lower border of the L4 vertebral body superiorly, and 1 cm lateral to the margins of the bony pelvis. The dose of radiation at the surface of the vaginal apex usually is boosted to 6,000 to 7,000 cGy by a variety of techniques. The most frequently reported side effects are gastrointestinal, usually abdominal cramps and diarrhea, although more serious complications such as bleeding, proctitis, bowel obstruction, and fistula can occur and may require surgical correction. The urinary system may be affected in the form of hematuria, cystitis, or fistula. The overall complication rate ranges from 25% to 40%; and the rate of serious complications requiring surgical intervention is about 1.5% to 3%.
External-beam pelvic radiation does not appear to impact survival in patients with high-risk stage I endometrial cancer. Patients with extrauterine pelvic disease, including adnexal spread, parametrial involvement, and pelvic lymph node metastases, in the absence of extrapelvic disease, are likely to benefit from postoperative pelvic radiation.
Extended-Field Radiation Patients with histologically proven para-aortic node metastases and no other evidence of disease spread outside the pelvis should be treated with extended-field radiation. The entire pelvis, common iliac lymph nodes, and para-aortic lymph nodes are included within the radiation field. The para-aortic radiation dose is limited to 4,500 to 5,000 cGy. Extended-field radiotherapy appears to improve survival in patients with endometrial cancer who have positive paraaortic lymph nodes (132,295–298).