A retrospective study evaluating the pretreatment tumor volume (PTV) in non-small cell lung cancer (NSCLC) as a predictor of response to program death-1 (PD-1) inhibitors

Introduction of hypothesis Little information is available regarding the imaging characteristics that assist in differentiating responders from non-responders. We hypothesized that patients with higher pretreatment tumor volume (PTV) would have lower response rates and shorter overall survival (OS). Methods Data from patients who received at least one dose of program death-1 (PD-1) inhibitors before August 31, 2016 were captured from our institution’s pharmacy database. The primary objective was to determine the association of PTV with best response, evaluated utilizing RECIST v1.1 criteria. Secondary objectives were estimation of progression-free survival (PFS) and OS. PTV was measured using the Philips Intellispace Multi-Modality Tumor Tracking application. Results 116 non-small cell lung cancer (NSCLC) patients were evaluated. 66% patients had adenocarcinoma, 28% had squamous cell carcinoma and 5% had poorly differentiated NSCLC. Median PTV was 53.7 cm3 (95% CI: 13.3–107.9). Only one individual had no metastases and the remainder had M1 disease; 38% M1a, 10% M1b, 51% M1c. Most (79%) were previously treated. There were no complete responses; among those followed for at least 6 weeks, 26% had a partial response, 39% stable disease and 34% PD; 4% had no recorded response. There were no strong associations of PTV with any of the demographic or clinical characteristics. There was no association between PTV and OS (HR 1.2, P=0.26) or PFS (HR 1.1, P=0.47). Liver metastasis was associated with shorter survival (HR=2.8, P=0.05). Conclusion PTV in NSCLC did not prove to be a predictor of response to PD-1 inhibitors but having liver metastasis was associated with significantly shorter survival.