GOG 99

GOG 99

A phase III trial of surgery with or without adjunctive external pelvic radiation therapy in intermediate risk endometrial adenocarcinoma: a Gynecologic Oncology Group study

Pubmed

Hypothesis:
Addition of external beam radiation to postoperative therapy in intermediate risk endometrial cancer improves recurrence free survival

Site: Endometrium

Study population:
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.

Experimental arm:
190 patients: External beam radiation 50.4 Gy given in 28 fractions. No Vag brachytherapy

Standard Arm:
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)

Conclusions:

  • 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.


Author: Shitanshu Uppal

Assistant Professor Gynecologic Oncology University of Michigan, Ann Arbor

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