The clinical usefulness of neuron-specific enolase (NSE), thymidine kinase (TK), and tissue polypeptide-specific antigen (TPS) was investigated in 41 patients (53-80 years old) with recently discovered small-cell lung cancer (SCLC). Eleven patients exhibited limited disease (LD) and 30 extensive disease (ED). Serum samples for NSE, TPS (immunoradiometric assay), and TK (radioenzymatic assay) evaluations were drawn from all patients at the time of diagnosis and before each cycle of chemotherapy in the treated patients. Therapy consisted of i.v. carboplatin 300 mg/m(2) on the first day and i.v. etoposide 120 mg/m(2) from the first to the third day every 3 weeks. Nine patients refused or were not eligible for chemotherapy. Five patients received only one course and showed no response (NR); 9 patients received two courses; 18 patients received three or more courses. In the last group, complete remission (CR) was obtained in 9 cases, partial remission (PR) in 18 cases. The tumor markers studied did not show any significant difference in distinguishing LD from ED. NSE and TPS were significantly more often abnormal than TK, either at the time of diagnosis (p < 0.05) or in PR or NR patients (p < 0.05). In relation to chemotherapy response, NSE and TPS serum patterns were shown to be more reliable than TK in PR (p < 0.05) and NR patients (computed error between 10% and 15%). No significant difference was observed between serum NSE and TPS patterns. Serum NSE and TPS seem to be more useful in the diagnosis and follow-up of SCLC patients undergoing chemotherapy. Further trials are necessary to ascertain whether the associated assessment of NSE and TPS can add useful information to that provided by the assessment of NSE alone.
