Adjuvant Radiation Field Extent and Sites of Failure in Node Positive Endometrioid Endometrial Cancer.

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Pract Radiat Oncol


washington; seattle; swedish cancer


OBJECTIVES: In patients with node-positive endometrial cancer, adjuvant radiotherapy with chemotherapy decreases local-regional recurrence compared to chemotherapy alone. However, optimal radiation field borders and extent of nodal coverage have not been well studied. In a multi-institutional cohort, survival outcomes and sites of failure were analyzed for patients with FIGO IIIC endometrioid endometrial cancer treated with pelvic (PRT) versus extended-field radiotherapy (EFRT), which encompassed high para-aortic lymph nodes.

METHODS: In a multi-institutional retrospective study, 143 patients with FIGO IIIC1 or IIIC2 endometrioid endometrial cancer treated with adjuvant radiotherapy from 2000-2016 were identified. Patient subgroups were classified by substage and radiation field extent: IIIC1 receiving EFRT, IIIC1 PRT, and IIIC2 EFRT. Recurrence-free (RFS), overall survival (OS) and out-of-field recurrence were calculated by Kaplan-Meier method. Multivariate analysis was performed by Cox proportional hazard. Sites of failure were categorized as within or outside the radiation field.

RESULTS: Median follow-up was 59 months; 87% received chemotherapy. Five-year RFS and OS rates were 73% and 87%, respectively. By subgroup, 5-year RFS rates were: 79% IIIC1 EFRT, 73% IIIC1 PRT and 69% IIIC2 EFRT (p=0.4). On MVA, recurrence risk was highest for IIIC2 EFRT, although not statistically significant (adjusted hazard ratio 2.0, p=0.4). In-field vaginal and nodal recurrences were observed in 2 (1%) and 4 (3%) patients, respectively. Of 78 stage IIIC1 patients treated with PRT, 5 (6%) had isolated para-aortic nodal relapse outside the radiation field; 3 were long-term survivors more than 6 years after salvage therapy. For patients with para-aortic recurrence, most had lymphovascular invasion (86%), ≥50% myometrial invasion (71%) and/or grade 3 disease (57%).

CONCLUSIONS: Adjuvant chemoradiotherapy results in excellent survival outcomes for patients with FIGO IIIC endometrioid endometrial cancer. For patients with positive pelvic nodes, isolated para-aortic relapse outside the PRT field was uncommon and amenable to salvage therapy.

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