Limited small cell lung cancer: prognostic significance of a complete response to the induction phase of chemotherapy followed by thoracic irradiation.
Limited-stage small cell lung cancer is frequently treated with induction combination chemotherapy (ICC), followed by consolidation with thoracic irradiation. It has been suggested that patients who do not have a complete response to ICC are unlikely to have control of occult distant metastasis and consequently have such a poor prognosis that thoracic irradiation is unlikely to be of benefit. To examine this hypothesis, 48 patients treated on prospective protocols who achieved a complete response to ICC or subsequently to thoracic irradiation were analyzed. Twenty-four patients had a complete response to ICC (CR-ICC), and 24 subsequently converted to complete-response status after thoracic irradiation (CR-TI). The two groups had similar prognostic factors and treatment. Comparing CR-ICC and CR-TI patients, survival was 40% versus 26% at 2 years and 35% versus 4% at 5 years, respectively (P less than .05). Freedom from distant metastasis was 41% at 5 years for the CR-ICC patients and 8% for the CR-TI patients (P less than .05). A modest number of CR-TI patients were long-term survivors, suggesting a value for thoracic irradiation as consolidation therapy.