The role of thoracic and cranial irradiation for small cell carcinoma of the lung

Since 1974, 120 previously untreated patients with small cell carcinoma of the lung seen in Therapeutic Radiology at The Medical College of Wisconsin have been entered into one of 4 successive studies. Study I used thoracic irradiation (TI) alone (4500-6000 rad in 3-6 weeks) with chemotherapy at progression. Study It randomized patients with limited disease to TI (3000 rad in 2 weeks) plus either cyclophosphamide, doxorubicin, vincristine (CAV) or total body irradiation (TBI); patients with extensive disease received TI + CAV. Study III employed prophylactic cranial irradiation (PCI) plus CAV and withheld TI unless there was incomplete response or recurrence. Of 93 evaluable patients from the first three studies, 55 had limited and 38 extensive disease. Study I (37 patients) showed a 62% complete response (CR) rate; 43% failed in the chest, 14% had brain metastases, and the median survival was only 22 weeks in spite of a preponderance of limited disease patients. Study II(27 patients) showed a CR of 59%; 30% had brain metastases and the median survival was 48 weeks. Study III patients (29) had a 69% rate; 72% failed in the chest, 4% with PCI developed brain metastases, and the median survival was 50 weeks. In March, 1979, Study IV was initiated; patients receive PCI (2500 rad in 2 weeks) plus high dose CAV, methotrexate and leucovorin. After 6 cycles, consolidation TI (3750 rad in 3 weeks) is given to patients with complete response. Preliminary results with 27 patients treated on this study show a 67% CR rate, a 41% chest failure rate (but only 11% for the patients who received thoracic irradiation) and no intracranial failures, but a 13% extracranial CNS failure rate. PCI, TI and spinal irradiation may be necessary to maximize the probability of long term disease free survival.