Omission of postoperative radiotherapy for early breast cancer

Dear Mr. Editor, We recently read an interesting article called “Postoperative radiotherapy omission in selected patients with early breast cancer following preoperative breast MRI (PROSPECT): primary results of a prospective two-arm study” published in the “LANCET – VOLUME 403, DECEMBER 2023”, in which it addresses omission of postoperative radiotherapy in selected patients by Gregory Bruce Mann and colleagues.[1] This prospective, multicenter, two-arm nonrandomized trial concluded that adjuvant radiation can be safely omitted in women with unifocal breast cancer on MRI and favorable surgical pathology with a radial margin of 2 mm or greater. However, we would like to point out several points that affected the study. First, it is a nonrandomized study. A total of 132 patients ineligible for omission of RT were excluded from the RT omission arm (Group 1) and included in those receiving RT (Group 2). So, Group 2 includes 21% of T2 and higher staged patients and 17% with node positivity (N1mi and N1a), whereas Group 1 had none. Also, Group 2 had 30% of patients who underwent re-excision surgery and 18% of patients did not receive radiotherapy. Second, breast MRI is not routinely done to detect occult lesions as conventional imaging and biopsy to detect suspicious lesions are cost-effective.[2] Third, the inclusion criterion was age above 50 years without any high-risk pathologies, which per say becomes an inclusion criterion for accelerated partial breast radiation (APBI), where radiation can be delivered intraoperatively without worrying about any long-term toxicities or cardiac complications.[3] Fourth, 11% of apparently unifocal cT1N0 breast cancer cases have malignant occult lesions, which further affirms the need for adjuvant radiation therapy to lower local recurrence risk. Last, PRIME II has shown that omission of radiotherapy resulted in a higher rate of local recurrence of 9.5% at 10 years with effect on distant metastasis or overall survival.[4] BASO trial showed with adjuvant radiation and hormonal therapy the local recurrence was 0% at 10 years.[5] To conclude, using available dates, we feel that omitting postoperative radiotherapy in favorable early-stage breast cancer might do more harm than benefit, especially where MRI is not a routine investigation of choice for detection of occult breast lesions. Given the concern for long-term toxicities, APBI can be considered as an alternative for these patients. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.