Prognostic influence of TNM staging and LDH levels in small cell carcinoma of the lung (SCCL)

To better define the prognostic factors influencing the response to therapy and survival in small cell carcinoma of the lung (SCCL), an expanded "TNM" type staging system was developed and investigated in a series of 73 protocol treated patients. Because serum LDH levels at disease presentation have been correlated to disease extent, response to therapy, and treatment outcome in a number of malignancies, including SCCL, these interrelationships were also analyzed in the protocol patients. The TNM system was found to be a more descriptive and specific "shorthand" for denoting sites of involvement and for indicating the body burden of tumor than the traditional limited-extensive disease (LD-ED) system. A clear statistical advantage could not be shown over the LD-ED system for predicting chemotherapy response or survival, although there were trends suggesting the TNM system could divide patients into three prognostic subgroups. Serum LDH proved to be a useful index of disease extent and therapy outcome. LDH levels at presentation were proportionately higher with more extensive tumor, measured by either the LD-ED or TNM staging. High LDH predicted poorer responses to chemotherapy and lower survival within similar stage subgroups compared to patients with normal LDH levels. The negative effect of elevated LDH was independent of hepatic involvement and did not predict subsequent hepatic failure in any consistent way. The SCCL TNM staging system proposed needs further refinement and should be tested with larger patient numbers. LDH, along with other tumor markers recently identified, need to be integrated into the staging system to form an overall prognostic index.