The Study: Uh, final manuscripts from previous ASCO abstracts, of course. If you can remember 2017, the initial abstract of GOG 258 helped nobody decide what the best approach is for high-risk endometrial cancer. Again, patients with any stage III/IVA disease or stage I/II serous or clear cell with positive peritoneal washings were enrolled. Ultimately, though, the large majority had endometrioid histology with nodal metastases. They received either  adjuvant 45 Gy radiation with concurrent cisplatin followed by carbo/taxol x 4 or  adjuvant carbo/taxol x 6. The final manuscript now reports recurrence-free survival at 5 years is still not different between arms at 58-59%. Instead, differences came in the form of toxicity and patterns of failure. Chemo alone had higher G3+ toxicity (58→ 63%) and double the rate of G4+ toxicity (14 → 30%). Chemo alone also resulted in higher rates of vaginal (2 → 7%) and pelvic/para-aortic (11 → 20%) recurrence but a lower rate of distant failure (27 → 21%). Compared to PORTEC-3, GOG 258 included more advanced nodal disease but comparable proportions of non-endometrioid histology. Meaning the “high-risk” in this trial was higher than the “high-risk” in PORTEC-3. In that context, GOG 258 shows that even though radiation reduces nodal and vaginal failures, that reduction isn’t enough to negate high rates of distant failure.
Bottom Line: The addition of pelvis radiation to chemo alone doesn’t appear to improve recurrence-free survival among women with high-risk (read: high nodal burden) endometrial cancer. | Matei, N Engl J Med 2019