Histologic subtypes of small cell carcinoma of the lung: Response to therapy

Seventy-seven patients with extensive small cell carcinoma of the lung were initially treated with the same combination chemotherapy consisting of cyclophosphamide and doxorubicin. All cases were retrospectively subdivided according to their histological subtype as proposed by the World Health Organization Lung Cancer Classification (WHO): the classic lymphocyte-like (oat cell), type 21, and intermediate cell, type 22. Type 21 has an objective response rate of 43% and type 22 a response rate of 23%. Analysis of the data revealed that the median survival for WHO type 21 was 30.4 weeks; whereas median survival for type 22 was 17.2 weeks (P = 0.04). This difference in subtype response was also seen when response was corrected for Karnofsky initial performance status 40–70 but not for performance status 80–100. Type 21 small cell carcinoma appears to offer a higher response rate to chemotherapy and a longer survival than type 22.