Prognostic factors differ by tumor stage for small cell lung cancer: a pooled analysis of North Central Cancer Treatment Group trials.

BACKGROUND: An analysis of 14 small cell lung cancer (SCLC) trials was performed to improve the current understanding of potential prognostic factors for overall survival (OS) and progression-free survival (PFS) in groups of patients with limited-stage disease SCLC (LD-SCLC) and extensive-stage disease SCLC (ED-SCLC) separately.

METHODS: Data on 688 patients with LD-SCLC and 910 patients with ED-SCLC were included. Clinical and laboratory factors were tested for their prognostic significance using Cox regression models that were stratified by protocol. Recursive partitioning and amalgamation (RPA) analyses were used to identify prognostic subgroups.

RESULTS: Poorer performance status (PS) led to worse OS and PFS in the ED-SCLC group but not in the LD-SCLC group. The prognostic impact of PS was strong for men but weak for women in the ED-SCLC group (interaction P value <.012 for OS and PFS). Other negative prognostic factors included increased age and men for the LD-SCLC group and increased age, men, increased number of metastatic sites at baseline, and increased creatinine levels for the ED-SCLC group. In patients with the ED-SCLC, RPA analyses identified 5 subgroups with different prognosis based on baseline PS, creatinine levels, sex, and the number of metastatic sites.

CONCLUSIONS: The current pooled analysis identified baseline creatinine levels and the number of metastatic sites as important prognostic factors in patients with ED-SCLC in addition to the well established factors of sex, age, and PS. There was a significant interaction between sex and PS within the ED-SCLC group, suggesting that PS is highly prognostic in men but has no significant impact in women. Within the LD-SCLC group, only age and sex were identified as important prognostic factors. RPA analyses confirmed many of these findings.