Location of recurrences in high-risk stage Iendometrial cancer patients not given postoperative radiotherapy: A Danish gynecological cancer group study.

Objectives: To study recurrence rates in Danish high-risk stage I endometrial cancers not given radiotherapy in accordance with the decision of the Danish Gynecological Cancer Group.

Methods: This prospective national cohort study includes all 4707 endometrial carcinomas diagnosed from 2005 to 2012. Of these, 623 patients had grade 3 endometroid adenocarcinoma with >50% myometrial invasion or serous/clear/undifferentiated carcinoma (with any depth of invasion). In 305 patients with high-risk stage I on final pathology, 14.1% received adjuvant external beam radiotherapy and 9.6% adjuvant chemotherapy. No patients received brachytherapy. 5-year Kaplan-Meier survival estimates and actuarial recurrence rates were calculated, and adjusted Cox regression analysis used for comparison. Recurrence rates were compared with historical Danish population data (DEMCA 98-99).

Results: For non-irradiated patients, 5-year overall survival, cancer-specific survival, and progression-free survival rates in high-risk stage I patients were 65%, 78%, and 73%, respectively. For non-irradiated patients, isolated local recurrences were uncommon (vaginal 3.1%, pelvic 0.4%). Death was mainly due to a high occurrence of non-local recurrences, with 8.8% experiencing a first recurrence in the abdominal cavity (outside the field where radiation traditionally have been given) and 13.0% a distant metastasis outside the abdominal cavity. Grade 3 tumors with >50% myometrial invasion seem to be characterized by a different pattern of recurrences, with significantly more isolated vaginal recurrences (7.9% vs 2.2%) and fewer total number of abdominal recurrences (7.9% vs 15.3%) as compared with unfavorable tumor types.

Conclusion: Isolated vaginal and pelvic recurrences were rare (3-5%) in patients with a final pathologic diagnosis of high-risk stage I endometrial cancer even after the Danish Gynecological Cancer Group decided to omit all types of postoperative radiotherapy and introduce lymph node staging.