A phase III trial of surgery with or without adjunctive external pelvic radiation therapy in intermediate risk endometrial adenocarcinoma: a Gynecologic Oncology Group study
Addition of external beam radiation to postoperative therapy in intermediate risk endometrial cancer improves recurrence free survival
Inclusion: Derived from GOG 33
- Intermediate Group: Any myometrial invasion with any grade and negative lymph node involvement i.e ([FIGO] stage IB, IC, IIA (occult), and IIB [occult]) – 5-year recurrence rate of 20 – 25%
- Lymph node – Sampling/debulking if suspicious; Full lymphadenectomy if no enlarged or suspicious nodes
- Revised during the course of study to enroll only “high intermediate risk” group : Expected 25% recurrence risk:
GOG 99 High Intermediate risk Group. Also used in GOG 249 - Age - G2-3 tumor - LVI - Outer 1/3 myometrial invasion 1) >70 yrs old with only 1 other risk factor 2) >50 yrs old with 2 risk factors 3) any age with 3 risk factors Excluded: High risk pathologies i.e. Clear cell and Papillary Serous, laparoscopic surgery excluded.
190 patients: External beam radiation 50.4 Gy given in 28 fractions. No Vag brachytherapy
202 patients: No additional therapy after surgery
Outcomes: Experimental arm vs. Standard arm (OR and p-values)
- Primary Outcome (Recurrence Free @ 24 months) – 3% vs. 12% (OR – 0.42, p=0.007)
- Secondary Outcome (Overall Survival @ 48 months) – 92% vs. 86% (OR – 0.86, p = 0.557)
- Local Recurrences – 1.6% vs. 8.9% (p = ss)
- Significantly Different Toxicity (Grade 2 or greater):
- Hematologic: 7.4% vs 2.5% (p = ss)
- GI : 34% vs. 2.5% (p = ss)
- Radiation reduced local recurrences but did not improve overall survival
- Many deaths in the study were not endometrial cancer specific, therefore study underpowered to detect difference in overall survival even if it existed.
- HIR group (132 total patients) : Defined above
- Reduction in Hazard of isolated recurrence (RH: 0.37)
- Reduction in Distant metastatic recurrence related to RT (RH: 0.46)
- 2/3rd of recurrences and 2/3rd of cancer deaths in this group.
- HIR – 19% improvement in cumulative recurrence at 24 months compared to no adjuvant therapy group vs LIR group 4% improvement compared to no adjuvant therapy group.
This study was the basis of GOG 249 selection criteria.