Tumor Burden Linked to Worse Survival in Rare Cancers Treated with Immunotherapy
A secondary analysis of the Southwest Oncology Group S1609 trial found that larger baseline tumor burden correlated with shorter overall survival but not progression-free survival in rare cancer patients treated with nivolumab plus ipilimumab. The study of 722 patients showed tumor burden was independently associated with survival outcomes but not predictive of tumor regression after dual immunotherapy.
Larger baseline tumor burden was associated with worse overall survival but not progression-free survival in patients with rare cancers treated with dual immune checkpoint inhibitors, according to a secondary analysis of a large phase 2 basket trial. The Southwest Oncology Group study S1609 evaluated nivolumab plus ipilimumab in 53 cohorts of patients with rare or ultrarare malignancies, with 722 patients included in this analysis.
In multivariable analysis, comparing a baseline tumor size of 12.9 cm or greater versus 1.0-4.8 cm yielded a hazard ratio of 1.64 for overall survival, with a 95% confidence interval of 1.02-1.72 and a p-value of 0.032. Higher baseline tumor burden quartiles showed only a weak negative association with any tumor regression at first scan, with a Fisher exact test p-value of 0.09. Both tumor burden and any tumor regression at the first posttreatment scan were independently associated with overall survival in multivariable analysis, though there was no evidence of an interaction between tumor burden and any tumor regression at the first scan.
The study defined baseline tumor burden as the sum of the greatest dimensions of target lesions at study registration, analyzed based on quartiles observed in the data. The number of target lesions was also considered a secondary tumor burden measure. The trial was conducted at over 1,000 sites as part of a National Cancer Institute/Southwest Oncology Group basket study evaluating the combination therapy in patients with measurable disease according to Response Evaluation Criteria in Solid Tumors version 1.1.
The findings indicate that larger baseline tumor burden was not predictive of tumor regression after dual immune checkpoint inhibitor therapy in this large cohort with rare cancer types. The research investigated whether pretreatment tumor burden correlates with overall survival, progression-free survival, and tumor regression among patients treated with dual immune checkpoint inhibitors for rare malignancies.