Impact of concomitant use of pazopanib and gastric acid suppressants on progression-free survival and safety in patients with sarcoma: a retrospective study.

Background: Pazopanib (PAZ) is an oral multi-kinase inhibitor used in the treatment of advanced soft tissue sarcoma. Gastric acid suppressants such as proton pump inhibitors (PPIs) and H2 receptor antagonists (H2RAs) may reduce PAZ absorption by increasing gastric pH, potentially affecting its efficacy. This study aimed to evaluate the impact of concomitant use of acid suppressants on progression-free survival (PFS) and safety in patients with soft tissue sarcoma.

Methods: This retrospective study included patients with advanced or metastatic soft tissue sarcoma who were treated with PAZ at a single institution between 2015 and 2022. Patients were divided into two groups: those who received PAZ with concomitant acid suppressants (AS combination group) and those who did not (non-AS group). The primary outcome was PFS. Kaplan-Meier curves were used to estimate survival, and group differences were compared using the log-rank test. Multivariable Cox proportional hazards regression was performed to adjust for confounding factors.

Results: A total of 99 patients were included (77 in the AS combination group, 22 in the non-AS group). The median PFS was 116 days in the AS combination group and 403 days in the non-AS group (hazard ratio [HR]: 1.42; 95% confidence interval [CI]: 0.68-2.85; P = 0.361). No statistically significant difference in PFS was observed. Adverse events of any grade occurred in 84% of patients in the AS combination group and 68% in the non-AS group. Grade ≥ 3 adverse events occurred in 33 patients (43%) in the AS combination group and 9 patients (41%) in the non-AS group.

Conclusions: In our cohort of sarcoma patients, the concomitant use of acid-suppressive agents was not associated with a statistically significant difference in PFS. However, the substantial numerical difference in median PFS observed between the groups (403 days vs. 116 days), coupled with the study's limited sample size, suggests a potentially clinically meaningful negative effect that warrants caution and further investigation in larger, prospective studies. Our findings, therefore, do not rule out a detrimental interaction and underscore the need for careful consideration when co-prescribing these agents with pazopanib in this patient population.