Experimental and clinical studies alternating chemotherapy and radiotherapy.

Clinical and experimental results with radiotherapy and chemotherapy for the treatment of cancer emphasize the necessity of giving treatment with both modalities with the greatest intensity possible in the initial phase of induction therapy. This can best be accomplished by utilizing new approaches, such as alternating the chemotherapy with newer methods of delivery of radiotherapy, which has the potential for greater destruction of tumor within acceptable limits of host toxicity. The clinical data from Institut Gustave Roussy, Villejuif, shows that alternating chemotherapy and radiotherapy produced an excellent complete response rate of 79% and a 4 year relapse-free survival rate of 22% in 109 patients with limited small cell lung cancer. Based on 5 year survival criteria, approximately one-fourth of the patients can be considered cured in 1 more year if no further change occurs. The results of the University of Virginia experimental studies have also demonstrated the superiority of alternating cyclophosphamide and radiotherapy in three courses of induction therapy over conventional methods of delivery of the two modalities. Using the experimental solid tumor 3924A, a cure rate of 50% or greater was obtained with this protocol with acceptable toxicity to the host, as opposed to no cures from three or more courses of either modality alone. One of the major deterrents to tumor cure with concomitant chemotherapy and radiotherapy has been excessive toxicity, which can be avoided by temporal separation (+/- 7 days) of the delivery of the two modalities without a significant loss of therapeutic effectiveness. Well-defined clinical protocols to determine how to more effectively interact chemotherapy with radiotherapy offer some of the greatest potential for a more rapid improvement in treatment.