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

The clinical courses of 418 patients with breast carcinoma who received postradical-mastectomy radiation therapy to the internal mammary and supraclavicular are were revied in order to determine the normal tissue tolerance with various time-dose fractionation radiation regimens. Four different dose fractionation schedules wereemplyed 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 similiar dose in 13 fractions in 21/2-3 weeks resulted in about 17% subcutaneous fibrosis. No significance of these clinical findings is discussed in relation to the various formulae currently being used to express time-dose equivalence.