OS More Affected by Tumor Rupture Than Surgery Type in GIST

Overall survival (OS) in patients with gastrointestinal stromal tumors (GIST) was impacted more by the presence of tumor rupture than quality of surgery (R1/R0) or treatment with adjuvant imatinib, according to a substudy of a phase 3 clinical trial (JAMA Surg. 2020 Apr 1. Epub ahead of print).

“The association between quality of surgery and [OS] in patients affected by localized [GIST] is not completely understood,” explained Alessandro Gronchi, MD, Fondazione IRCCS Istituto Nazionale dei Tumori, Milan, Italy and co-investigators, who assessed the risk for death by microscopic margins status (R0/R1) with or without adjuvant imatinib.

The cohort substudy by Dr Gronchi et al used data from a trial that took place between December 2004 and October 2008 across 112 hospitals. Patients had to be aged >18 years, have intermediate or high risk for relapse, and have no evidence of residual disease after surgery or other severe medical conditions.

A total of 908 patients included in the analysis were randomized after surgery to receive 2 years of imatinib or no adjuvant therapy. Patients were stratified by treatment center, risk, tumor site, and quality of surgery (R0 vs R1).

The primary end point of the substudy was OS. Using Cox models adjusted for treatment and stratification factors, OS was compared between arms that underwent R0 and R1 resection.

The median follow-up was 9.1 years. Of 162 patients who had an R1 resection, 97 had tumor ruptures.

Dr Gronchi and colleagues observed a significant difference in OS depending on whether patients had R1 or R0 resections (hazard ratio [HR], 2.05; 95% CI, 1.45-2.89) and whether they received adjuvant imatinib treatment (HR, 2.65; 95% CI, 1.37-3.75) or not (HR, 1.86; 95% CI, 1.16-2.99).

Of note, the difference in OS between arms who underwent R1 versus R0 resections disappeared upon exclusion of tumor rupture (HR, 1.05; 95% CI, 0.54-2.01).

“The difference in OS by quality of surgery with or without imatinib was associated with the presence of tumor rupture. When the latter was excluded, the presence of R1 margins was not associated with worse OS,” concluded Dr Gronchi and co-investigators.—Kaitlyn Manasterski