Twice daily thoracic irradiation for limited small cell lung cancer.
Thoracic failure is a significant obstacle to the cure of limited stage small-cell lung cancer (LSCLC) patients treated with combined modality therapy. In 1985 we initiated a prospective trial to evaluate the impact of twice daily thoracic irradiation without concomitant chemotherapy on control of intrathoracic tumor in LSCLC. Twenty-nine patients treated in this fashion were compared with 36 patients treated from 1979-1982 with once daily thoracic irradiation and concomitant chemotherapy. Both groups received the same induction chemotherapy; cyclophosphamide, Adriamycin, and vincristine (CAV) alternating with cisplatin and etoposide. For consolidation, the twice daily patients received thoracic irradiation, 45 Gy in 1.5 Gy fractions given twice daily, and the once daily patients received thoracic irradiation, 45 Gy in 2.5 Gy fractions given once daily with concomitant cyclophosphamide and vincristine. After completion of radiotherapy both groups received maintenance chemotherapy. The complete response (CR) rate after thoracic irradiation was higher for twice daily patients (86% (25/29) compared to the once daily patients [61% (22/36), p = 0.02]. However, this advantage was offset by the shorter duration of thoracic control among CR patients treated with twice daily thoracic irradiation compared to once daily thoracic irradiation (32% vs 67% at 2 years, p less than 0.05). In view of the enhanced initial response of LSCLC to twice daily thoracic irradiation, this basic radiotherapeutic approach seems appropriate, but new strategies using higher doses of twice daily thoracic irradiation or concomitant chemotherapy appear to be necessary to enhance long-term thoracic control.