The influence of dose fractionation on acute and late reactions in patients with postoperative radiotherapy for carcinoma of the breast

Abstract

The clinical courses of 418 patients with breast carcinoma who received post‐radical‐mastectomy radiation therapy to the internal mammary and supraclavicular area were reviewed in order to determine the normal tissue tolerance with various time‐dose fractionation radiation regimens. Four different dose fractionation schedules were employed during the period 1958–1968 at Memorial Hospital: 4900 rads/10f/32d; 4410 rads/9f/30d; 5000 rads/13f/18d; and 4600 rads/20f/28d. There was no difference in the acute reaction or local recurrence rate of the tumor in the irradiated area among the four fractionation schemes, but the late effects were quite different. Patients who received 4900 rads in 10 fractions in 32 days had a 33% incidence of subcutaneous fibrosis. A similar dose in 13 fractions in 21/2–3 weeks resulted in about 17% subcutaneous fibrosis. No significant late effects were observed in the patients who received either 4600 rads in 20 fractions or 4410 rads in 9 fractions in 4 weeks. The significance of these clinical findings is discussed in relation to the various formulae currently being used to express time‐dose equivalence. Copyright © 1975 American Cancer Society