The maximum tumor growth rate predicts clinical outcomes of patients with small-cell lung cancer undergoing first-line chemotherapy plus immune-checkpoint inhibitor therapy

Abstract

Background: Currently, no biomarkers can accurately predict survival outcomes in patients with SCLC undergoing treatment. Tumor growth rate (TGR; percent size change per month [%/m]) is suggested as an imaging predictor of response to anti-cancer treatment. We aimed to evaluate the predictive role of the maximum TGR (TGRmax) for outcomes of small-cell lung cancer (SCLC) patients undergoing first-line chemotherapy plus immune-checkpoint inhibitor (ICI) treatment.

Methods: Patients with SCLC receiving first-line chemotherapy plus immunotherapy were analyzed within this retrospective study. The X-tile program was used to identify the cut-off value of TGRmax based on maximum progression-free survival (PFS) stratification. The Kaplan-Meier methods and Cox regression models were used to evaluate the effect of the presence of TGRmax on PFS and overall survival (OS).

Results: In total, 104 patients were evaluated. Median (range) TGRmax was -33.9 (-65.2 to 21.6) %/m and the optimal cut-off value of TGRmax was -34.3%/m. Multivariate Cox regression analysis revealed that patients with TGRmax > -34.3%/m was associated with shorter PFS (hazard ratio [HR], 2.81; 95% CI, 1.71-4.63; p < 0.001) and OS (HR, 3.17; 95% CI, 1.41-7.08; p = 0.005). In patients who received partial response (PR), Kaplan-Meier survival analyses showed that superior PFS and OS (p = 0.005 and p = 0.009, respectively) benefit was observed when TGRmax ≤-34.3%/m.

Conclusions: SCLC patients with TGRmax > -34.3%/m had worse PFS and OS in first-line ICI plus platin-based chemotherapy. TGRmax could independently serve as an early biomarker to predict the benefit from chemoimmunotherapy.

Keywords: SCLC; chemoimmunotherapy; first-line treatment; small cell lung cancer; survival; tumor growth rate.