Prognostic significance of histopathologic subtype and stage in small cell lung cancer

A study of 149 light microscopic tissue slides from 147 patients with recorded initial diagnoses of small cell lung cancer (SCLC) (114 cases) and undifferentiated carcinoma (35 cases) was undertaken to test the reproducibility and prognostic impact of a new histopathologic subclassification of SCLC proposed by the Pathology Panel of the International Association for the Study of Lung Cancer (IASLC). This study was further designed to test the impact of clinical stage, age, sex, and race on survival. The tissue slides were blindly reclassified as SCLC or non-SCLC by a panel of five pathologists with no knowledge of the initial diagnosis. The SCLCs were divided into the three subtypes outlined by the IASLC pathology panel: small (classic or pure), mixed (small cell/large cell), and combined (small cell/squamous carcinoma or small cell/adenocarcinoma). Small cell lung cancer was clinically staged as local, regional, or distant. Consensus diagnosis (defined as agreement by at least three of the five pathologists) was achieved in 144 (96.6%) of the 149 cases. Of these 144 cases, 124 were reclassified as SCLC (115 [92.8%] small, five [4.0%] mixed, and four [3.2%] combined) and 20 were classified as non-SCLC. The median lengths of survival for the small, mixed, and combined subtypes were 225, 1,110, and 203 days, respectively (P = .025). Adequate staging data were available in 123 of the 124 SCLC cases. Of the 123 SCLC cases, 27 (21.9%) were local, 22 (17.9%) were regional, and 74 (60.2%) were distant stage. The median lengths of survival for the local, regional, and distant stages were 428, 251, and 111 days, respectively. This association was highly significant (P = .0001). We conclude that stage is the major determinant of survival in SCLC. Mixed subtypes had significantly longer survival times than the small or combined subtypes (P = .025). Survival times were longer for women than for men, and the survival time difference between men and women was significant (P = .0028). We found no significant differences in survival according to age or race.