Endocrine Therapy Supports Safe Radiation De-Escalation in Early-Stage Breast Cancer

At the San Antonio Breast Cancer Symposium (SABCS) in San Antonio, Jose Bazan, MD, discussed real-world radiation treatment patterns among patients with early-stage breast cancer and axillary micrometastatic disease. The secondary analysis evaluated patients treated between 2011 and 2014 and showed that only 15% of patients received regional nodal irradiation, reflecting a de-escalated approach consistent with current clinical practice. Patients who underwent mastectomy rarely received radiotherapy, reinforcing the perception that this population represents a low-risk group. Bazan noted that there is no randomized clinical trial evidence supporting comprehensive nodal irradiation in patients with micrometastases, and the observed treatment patterns suggest appropriate risk-adapted care. As radiation is omitted or de-escalated, endocrine therapy plays a central role in controlling micrometastatic disease. Bazan emphasized the importance of multidisciplinary follow-up, particularly pharmacist involvement, to support endocrine therapy adherence and optimize long-term outcomes in these patients.

Pharmacy Times: What do these real-world radiation patterns from S1007 tell us about how clinicians currently view the risk of pN1mi disease, particularly compared with macro metastatic nodal involvement?

Jose Bazan, MD: That’s a great question. Thank you so much. First of all, I want to make sure that we understand the patients that we looked at for this secondary analysis. They were treated from 2011 to 2014, so more than 10 years ago for most of those patients. I think I was really reassured by what we found in the study, in that the way most of us approach patients today is the way that a lot of the patients on the RxPONDER trial with micrometastases were treated with regard to radiation.

We have absolutely no randomized clinical trial data showing that comprehensive treatment of the breast or chest wall and lymph nodes is beneficial in patients with micrometastatic disease. I think we were all reassured to find that only 15% of these 573 patients received regional nodal radiation. I was really glad to see that of the patients who had mastectomies, very few of them received any radiotherapy, because I think it confirms what we’ve all thought—that these are very low-risk patient populations. The radiation oncologists treated patients appropriately, and once we get the outcomes data, we’ll be able to confirm that these patients did really well, which is what we expect.

Pharmacy Times: From a multidisciplinary perspective, how important is it for pharmacists and other care team members to understand radiation patterns when counseling patients on endocrine therapy adherence and long-term toxicity?

Jose Bazan, MD: That’s another excellent question. What it comes down to with endocrine therapy and radiation therapy, especially when we’re talking about de-escalating radiation therapy, is that we are relying on the endocrine therapy to take care of micrometastatic foci of disease that may be in the axilla, other lymph nodes, or other parts of the body. By omitting radiation or de-escalating radiation, such as after a lumpectomy to treat just the breast as opposed to the breast and lymph nodes, we are making the assumption that the patient is going to take their five, or however many years, of endocrine therapy is appropriate.

I think it’s important for all of us—pharmacists, radiation oncologists, medical oncologists, and surgeons—when we see these patients in follow-up, to make sure that we help them get through their endocrine therapy and work with them, because we are really relying on that therapy for disease control, especially in these de-escalated situations.