Prognostic significance of initial tumor shrinkage in patients with stage III non-small cell lung cancer treated with durvalumab following chemoradiotherapy.

ABSTRACT

BACKGROUND: Baseline tumor size (BTS) is one of the prognostic factors of advanced non-small cell lung cancer (NSCLC) treated with immunotherapy. However, its prognostic value in patients with locally advanced NSCLC receiving durvalumab maintenance therapy remains unclear. METHODS: The present study retrospectively reviewed 136 patients with unresectable stage III NSCLC who underwent CRT and durvalumab at two institutions in Japan. The maximum diameter of the target lesion (max BTS) before CRT was measured, the best response to CRT before durvalumab was evaluated, and the impact of the response on durvalumab was explored. Progression-free survival (PFS) and overall survival (OS) were defined as the time from the day of starting durvalumab. RESULTS: Of the total cohort, 133 (97.8%) patients had at least one measurable lesion. The best response to CRT resulting in CR, PR, and SD was seen in 0 (0%), 69 (51.9%), and 64 (48.1%) patients, respectively. PFS was significantly longer in the patients with PR than in those with SD after CRT (median not reached vs. 20.0 months; HR 0.51; P = 0.023). Moreover, the absence of a massive lesion (max BTS < 50 mm) was associated with a superior CRT response (P < 0.001). CONCLUSION: The best response to induction CRT was associated with better PFS in patients with stage III NSCLC receiving durvalumab following chemoradiotherapy. Although the absence of a massive lesion was associated with a better response to induction CRT in this cohort, this was not translated into PFS and OS benefit.