Breast irradiation following breast-conserving surgery significantly decreases the risk of recurrence in the breast. In the NSABP B-6 trial, breast irradiation following breast-conserving surgery in women age 70 or younger decreased the local recurrence rate from 39% to approximately 10%. The Milan group confirmed the risk reduction with breast irradiation, revealing that 0.3% of women in their study developed local recurrence after radiation compared to 8.8% of women who did not receive adjuvant radiation therapy with median follow-up of 39 months. Despite the significant improvement in local recurrence rates, the omission of radiation therapy following conservative surgery does not appear to compromise survival. Among older women, there have been conflicting reports regarding the benefits of adjuvant breast irradiation. There is some evidence that the risk of recurrence in the breast decreases with age, with recurrence rates reported as less than 4% in older women after breast-conserving surgery without radiation. Other studies have shown a risk of recurrence of more than 20% in elderly patients who do not receive adjuvant radiation after lumpectomy or partial mastectomy.

The Cancer and Leukemia Group B has completed accrual to a trial designed to test the value of radiation in older women, but there are no results available at this time. Although radiation therapy may provide only modest benefit in older women, breast irradiation should not be omitted based on advanced age alone in the absence of additional findings from clinical trials. Importantly, breast irradiation appears to be well tolerated in older women. On the other hand, it is reasonable to consider omitting breast radiation in an individual of any age who has multiple comorbid conditions and is unlikely to survive more than a few years.