Women over age 65 who undergo breast-conserving surgery and hormone therapy for hormone receptor-positive, node-negative breast cancer may be able to skip radiation therapy, according to the results of a study presented at the 2013 San Antonio Breast Cancer Symposium (SABCS).
Early breast cancer is often treated with the surgical removal of the cancer (referred to as lumpectomy or breast-conserving surgery) followed by radiation therapy to kill any remaining cancer cells. However, as the use of effective systemic therapy (such as hormone therapy) has increased, the rate of local recurrence after breast-conserving surgery has fallen—leading researchers to speculate that radiation therapy could be omitted in select patients.
To evaluate this theory, researchers conducted the PRIME 2 study, an international, phase III, randomized trial designed to determine whether whole-breast radiation therapy could be omitted in subgroups of older patients receiving appropriate therapy. The study included 1,326 patients randomly assigned to receive or forego radiation therapy. All of the women in the study were over age 65 and had early stage hormone-positive, node-negative breast cancer. The primary endpoint of the study was recurrence of breast cancer in the same breast, known as ipsilateral breast tumor recurrence (IBTR).
At five years, there was no significant difference between patients who received radiation and those who did not in terms of overall survival (97% vs. 96.4%), regional recurrence (0.5% vs. 0.8%), or breast cancer in the opposite breast (0.5% vs. 0.7%). IBTR at five years was 2.7 percent without radiation therapy and 0.6 percent with it. The difference in breast cancer-free survival between women receiving radiation (98.5%) and those not receiving radiation (96.4%) was statistically significant, however. This was due to the greater IBTR in the group that did not receive radiation.
The researchers concluded that although radiation reduces IBTR significantly, the absolute reduction is very small. Put simply, for every 100 women treated with radiation, four will have a recurrence prevented, one will have a recurrence, and 95 will have undergone unnecessary treatment. What’s more, once a patient has radiation, they cannot have it again on the same breast—so for some women, it might be better to “save” the option of radiation therapy in case there is a recurrence.
The researchers concluded that some women older than age 65 with hormone-positive, node-negative early breast cancer can forego radiation therapy and instead have breast-conserving therapy and hormone therapy.
Kunkler IH, Williams LW, Jack W, et al. The PRIME 2 trial: Wide local excision and adjuvant hormonal therapy ± postoperative whole breast irradiation in women older than 65 years with breast cancer managed by breast conservation. San Antonio Breast Cancer Symposium December 10-14, 2013. Abstract S2-01.