The role of radiation oncology in small cell lung cancer

Abstract

Small cell lung cancer comprises a histologic subgroup of bronchogenic carcinomas distinguished particularly by a responsiveness to cytotoxic agents, and equally by a strong tendency to disseminate, both to mediastinal and distant sites. At one time considered suitable only for short-term palliation by radiation therapy, this disease is now managed by both systemic and regional approaches, typically with close integration of radiotherapy and chemotherapy. Thoracic irradiation produces modest improvements in both survival and local control in small cell lung cancer, when the clinical extent is limited to the chest. The optimal parameters of dose, treatment volume, fractionation, and temporal integration with chemotherapy are not yet defined. When the disease is more extensive radiotherapy plays a useful palliative role. New biological insights are being brought to the clinic, and have stimulated new therapeutic initiatives in the treatment of this disease. Modified radiotherapy fractionation schemes and sophisticated integration of chemotherapy and radiation therapy have resulted in further advances. In addition to improved response rates and median survivals, combined modality approaches suggest, in addition, the possibility of cured subset in cases of disease confined to the chest. The adverse effects of thoracic irradiation are manageable and the more serious can be prevented with careful attention to volume and technique. Radiotherapy offers relief of many symptoms and cost-effective palliation of metastatic lesions in most body sites. Considered as a significant problem in oncology, and apart from efforts at primary prevention, major progress in this disease is most likely to result from research focussed on the limited disease subset, which, unfortunately, consists of no more than half the incident cases. These patients have a median survival of 12-18 months, and are sufficiently numerous that it is possible to detect meaningful treatment progress in clinical trials of a reasonable size. Nevertheless, the marked advances of two decades ago, when chemotherapy first came into widespread use, are not seen today. Progress is now more likely to be seen in modest improvements in survival or tumor control rates when control and experimental regimens are compared statistically in large trials or in meta-analyses. While the evidence supports the use of thoracic radiotherapy the ideal drug combination is unknown, and there is a real need for new agents of substantially greater activity than those available today. While more rational combinations of agents may be possible, it seems likely that the limits of tolerance are being reached.(ABSTRACT TRUNCATED AT 400 WORDS)