TARGIT-B IORT Boost Blunts Distant Relapse in Young Patients With Breast Cancer

In an interview with CancerNetwork® at the 2026 American Society for Radiation Oncology (ASTRO) Annual Meeting, Leah Katz, MD, MPH, vice chair of Faculty Development and an attending radiation oncologist in the Department of Radiation Oncology at the University of Miami Leonard M. Miller School of Medicine, discussed initial outcomes from the international, randomized phase 3 TARGIT-B trial (NCT01792726). The trial compared a targeted intraoperative radiotherapy (TARGIT-IORT) tumor bed boost delivered during lumpectomy with a postoperative external beam radiotherapy (EBRT) boost in young or higher-risk patients with breast cancer; all patients received whole breast radiotherapy.

Among 1684 randomly assigned patients with a median follow-up of 4.2 years, 4-year local recurrence rates were low in both arms (2.3% vs 2.1%). Overall distant relapse did not differ significantly (HR, 0.68; 95% CI, 0.43-1.06; P = .087). However, in the subgroup of 544 young patients, the 7-year distant relapse rate was 4.3% with the IORT boost vs 17.0% with the EBRT boost (HR, 0.33; 95% CI, 0.16-0.68; P = .0016). Among patients who had a local recurrence, subsequent distant relapse was also lower with the IORT boost (HR, 0.32; 95% CI, 0.12-0.89; P = .03).

Katz highlighted this potential blunting of distant metastatic spread as the most intriguing aspect of the study.

Transcript:

CancerNetwork: TARGIT-B tests an intraoperative tumor-bed boost for young/high-risk patients, how does that change the sequencing conversation with surgery?

Katz: The TARGIT-B study showed equivalent local recurrence with an intraoperative radiotherapy boost vs an external beam boost, so we know that it’s safe. The more interesting conversation about the TARGIT-B study, which I address in my talk, is that it also decreased distant metastatic recurrence. We know that a local recurrence increases your distant metastatic rate, for reasons that are not scientifically clarified yet but are going to be very interesting for us to elucidate. The boost blunted that effect, which is incredibly interesting. What will happen in the future, after more studies and more stratification are done, is that there’s going to be a biologically advantageous group to offer the TARGIT boost to.

Reference

Vaidya JS, Bulsara MK, Tobias JS, et al. Initial outcome of the TARGIT-B international randomised trial of targeted intraoperative radiotherapy tumour bed boost for young or high-risk patients with breast cancer. Presented at: 2026 ASTRO Annual Meeting; September 26-30, 2026; Boston, MA. Abstract 349.