Effect of histological subtype and treatment modalities on T1-2 N0-1 small cell lung cancer: A population-based study

Combined small cell lung cancer (C-SCLC) is rare and its clinical features, appropriate treatment, and prognosis are poorly understood. Reports conflict over the prognosis of C-SCLCs compared to pure small cell lung cancer.

The records of patients diagnosed with primary SCLC from 1988 to 2014 were extracted from the Surveillance, Epidemiology, and End Results database. The general features of C-SCLCs were compared to those of SCLCs. T1-2 N0-1 data was extracted and the effects of the histological subtype, treatment modality, and other prognostic factors on lung cancer-specific survival (CSS) was analyzed in a 3:1 matched dataset. Analysis was performed using the 8th edition tumor node metastasis staging system and previous staging systems adjunctively.

C-SCLCs comprised 1.5% of all SCLCs (1486/98 667); 184 cases of C-SCLCs and 2681 cases of non-combined SCLCs (NC-SCLCs) were included in this study. C-SCLCs were more likely to be of a higher grade and to occur in the upper lobe than NC-SCLCs. Before matching, C-SCLCs showed better CSS (hazard ratio 0.69; P < 0.001). However, stratified Cox proportional hazards analysis in the matched dataset revealed that only treatment modality and age at diagnosis were associated with CSS; the histological subtype had no effect on survival. Of all treatment modalities, surgery with chemoradiation showed the best CSS in T1-2 N0-1 SCLC.

In early SCLC, surgery with chemoradiation shows the best CSS. C-SCLC patients might benefit more from multimodal treatments, including surgery, than SCLC patients.