For women who have a lumpectomy or breast-conserving surgery, radiation is a standard element in treatment. And we know from classic studies from the National Surgical Adjuvant Breast and Bowel Project (NSABP) and others that women who have a mastectomy actually have the exact same survival as women who have a lumpectomy, provided that the women who have a lumpectomy additionally receive radiation treatment.^[1] The question that arises frequently for older women, typically defined as age 65 or 70 or older, is whether it essential to include radiation therapy? And there have been two studies that have looked at the possibility of omitting radiation treatment in older women with estrogen receptor (ER)–positive breast cancer after lumpectomy. 

The first study, from Cancer and Leukemia Group B (CALGB), was led by Kevin Hughes and compared endocrine therapy alone versus endocrine therapy plus radiation treatment.^[2,3]It showed that radiation therapy had no impact on long-term survival. However, women who had radiation treatment did have a lower risk of in-breast recurrence. It went to about 2%, with women who did not have radiation having about a 10% or 12% risk of in-breast recurrence. Again, that’s not overall survival, but it does lower the risk of an event within the breast over the next decade. 

The PRIME II study was a European-based study that also asked a question, can women with ER-positive breast cancer omit radiation after lumpectomy if they are older? And fundamentally, the PRIME II study reached the same conclusion, that there was no impact on overall survival amongst older women, but there was a small decrease in the risk of in-breast recurrence.^[4]

So what do we actually do in clinic? For many older women, particularly 75 years and older, I think it’s very comfortable to say that they may omit radiation therapy. The risk of in-breast recurrence is generally low, and there will be no impact on survival. For very vigorous women in their late 60s, early 70s, I think you can also point to these data and say that radiation therapy may lower their risk of in-breast recurrence. And since radiation is generally well tolerated, it can be a good option for such women who have a life expectancy well beyond 10 years. Finally, it’s important to remember that these studies assume that the patient will be taking antiestrogen adjuvant therapy. If there is a reason to believe that the patient will not be taking tamoxifen or an aromatase inhibitor or other appropriate endocrine treatment, then you can’t rely on the endocrine therapy to control in-breast recurrence, and those women should receive radiation treatment after lumpectomy.