The radiation therapy oncology group experience altered fractionation in lung cancer

Abstract

A major activity of the Radiation Therapy Oncology Group (RTOG) during the past 20 years has been clinical trial development in bronchogenic carcinoma. In RTOG 73-01, the group was able to demonstrate a dose response to external beam irradiation in unresectable lung cancer. In spite of an improved response rate and a short-term benefit in survival, no long-term benefit in survival has been demonstrated (Table 1). Patients continue to exhibit a high incidence of local failure (-70%) with longer follow-up. In order to improve these results, the RTOG has conducted a series of randomized trials evaluating biologic response modifiers, hypoxic cell sensitizers, altered fractionation and chemo-sensitization. Trials involving hypoxic sensitizers and biologics have not yielded positive results for these agents. Phase III trials involving altered fractionation and chemotherapy are ongoing. The purpose of this report is to summarize the group’s activities with altered fractionation in lung cancer. Table 2 lists group studies designed to test altered fractionation in all disease sites. We can define “standard fractionation” as 1.8 to 2.0 Gy delivered as a single fraction daily, 5 days per week, to 60 to 70 Gy. Variations on this schedule constitute altered fraction. Discussion will be limited to the schedules defined as follows: Hyper~kzctionution: The size of the dose per fraction is reduced, the number of total fractions is increased, the total dose is slightly increased and the overall time is relatively unchanged. Treatment is usually given two or more times daily. Hypofractionation: The size of the dose per fraction is increased, the number of dose fractions is decreased, the total dose is decreased and the relative time is unchanged. Treatment is usually given one to three times a week. Accelerated fractionation: The overall time of treatment is significantly reduced, the