When Standards Meet Reality: An Inverted PORTEC-3 Protocol for High-Risk Endometrial Cancer in Resource-Limited...

Background/Objectives: The combination of chemotherapy and radiotherapy represents a standard adjuvant treatment for patients with high-risk endometrial cancer. However, limited access to radiotherapy in many healthcare systems frequently results in treatment delays, potentially compromising outcomes. The aim of this study was to evaluate the oncologic outcomes and toxicity profile of an inverted treatment sequence consisting of upfront chemotherapy followed by concurrent chemoradiotherapy. Methods: We conducted a retrospective single-center study including patients with non-metastatic high-risk endometrial cancer. Eligible patients had FIGO stage I grade 3 disease with lymphovascular space invasion, stage II-III disease, or non-endometrioid histology. All patients received four cycles of paclitaxel-carboplatin followed by pelvic radiotherapy with concurrent cisplatin. Survival outcomes, including local recurrence-free survival, disease-free survival, metastasis-free survival, and overall survival, were analyzed using the Kaplan-Meier method and Cox proportional hazards models. Acute hematologic toxicity was graded according to CTCAE v5.0. Bone marrow dose-volume parameters were evaluated, and receiver operating characteristic curve analysis was performed to identify thresholds associated with grade ≥ 2 hematologic toxicity. Results: Fifty-two patients were included, with a median follow-up of 31.4 months. Five-year overall survival and disease-free survival rates were 86.1% and 77.5%, respectively. Ten patients relapsed, with distant metastases observed in all cases and synchronous local recurrence in one. Delays between surgery and radiotherapy of 20 weeks or more, as well as delays exceeding 10 weeks before initiation of chemotherapy, were associated with significantly reduced disease-free survival. Grade ≥ 2 hematologic toxicity was frequent, and neutropenia was associated with inferior overall survival. Bone marrow dose-volume thresholds predictive of hematologic toxicity included V40 Gy < 20-25% and V30 Gy < 40%. Conclusions: A chemotherapy-first adjuvant strategy provides favorable oncologic outcomes and excellent locoregional control in high-risk endometrial cancer when radiotherapy is delayed. However, increased hematologic toxicity highlights the importance of optimized bone marrow sparing.