The impact of radiotherapy on the incidence and time of occurrence of local recurrence in early-stage breast cancer after breast conserving therapy.

There is still little information on the delay of local recurrence after conservatively treated and irradiation breast cancer. To evaluate the impact of radiation therapy (RT) on the incidence and on the time of occurrence of ipsilateral breast tumor recurrence (IBTR), we reviewed the treatment results in 415 women with UICC Stage I or II unilateral breast cancer. All underwent breast conserving surgery (BCS) and full axillary dissection between 1983 and 1987. Out of them 309 patients were irradiated and 106 were not. The median dose of RT was 50 Gy in five weeks to the whole breast. Systemic therapy, when it was given, consisted of 6-cycles of CMF for node positive premenopausal women and 20 mg tamoxifen for three years for postmenopausal women. The median follow up time was 120 months in survivors. The 10-year actuarial IBTR rate was 36.6% for the nonirradiated and 9.1% for the irradiated women (p = 0.0000); 48.6% for patients treated with CMF and 4.2% for those treated with CMF plus RT (p = 0.0051); 29.0% for patients treated with tamoxifen and 7.9% for those treated with tamoxifen plus RT (p = 0.0318). The patient's age and the presence of an extensive intraductal component (EIC) were both highly associated with the likelihood of tumor recurrence in the treated breast. Patients under 41 years of age had an actuarial 10-year IBTR rate of 75% without RT and 17. 1% with RT (p = 0.0006). Women with an EIC positive tumor had an IBTR rate of 88.9% when RT was not given and 27.2% when RT was given (p = 0.0003). In invasive lobular cancer, irradiated patients had a IBTR rate of 2.3%, compared to 53.2% for nonirradiated patients (p = 0.0008). RT resulted in a significant delay in the appearance of IBTR (p = 0.0250) and the median time was increased by 20.0 months. We conclude that RT has the property of not only preventing but also delaying IBTR. In invasive lobular tumors the risk of IBTR is very high when RT is omitted, but BCS plus radiation therapy is effective treatment. Patients wih EIC positive tumor are at high risk of IBTR even when a median dose of 50 Gy is given to the whole breast.