Past

Standard of care for low-risk breast cancer patients is breast conserving surgery (BCS) followed by partial breast irradiation (PBI). Postoperative PBI leads to unnecessary large irradiated breast volumes due to artifacts, including seroma.1 Preoperative PBI allows more precise target volume definition as the tumor is still in situ, and more importantly carries the possibility of tumor downstaging.

Present

Recent studies have reported good to excellent clinical and oncological outcomes in patients treated with preoperative PBI followed by BCS.2 Five studies reported results on single-dose external beam preoperative PBI ranging between 15 and 21 Gy.2 Treatment with this relatively high dose led to mainly mild toxicity and good to excellent cosmetic outcomes in the majority of the patients. A remarkable result is the increased rate of pathologic complete response (pCR) after a longer interval of 6–8 months (42%) in comparison with a shorter interval of 2–8 weeks between radiotherapy and surgery (0–15%).2 Therefore, extending the interval could lead to an even higher response rate.

Future

The ultimate goal is to omit surgery in future low-risk patients with a pCR. For this purpose, it is necessary to be able to predict a pCR accurately after single-dose PBI. Even when patients do not reach a pCR after preoperative PBI, the advantage of this approach is single-dose radiotherapy instead of the standard multi-fractionated radiotherapy (i.e., 5–15 fractions).3 This could reduce the treatment burden, facilitate healthcare logistics, and reduce healthcare costs. The positive predictive value of magnetic resonance imaging (MRI) alone is 67%, which is not sufficient to predict a pCR.4 Combining MRI parameters with biomarkers, such as gene expression profiling, specific immune profiles, and circulating tumor DNA could result in more accurate prediction of pCR after preoperative single-dose PBI in low-risk breast cancer patients.5