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Delayed Targeted Intraoperative RT Yields Similar OS to EBRT in Early Breast Cancer

Among patients with early breast cancer in a prospective study, delayed targeted intraoperative radiotherapy (TARGIT-IORT) administered via a reopened lumpectomy incision yielded long-term OS similar to that of whole-breast external beam radiotherapy (EBRT), despite higher local recurrence (JAMA Oncol. 2020 Apr 2. Epub ahead of print).

“Conventional adjuvant [RT] for breast cancer given daily for several weeks is onerous and expensive. Some patients may be obliged to choose a mastectomy instead, and some may forgo [RT] altogether,” according to Jayant S. Vaidya, MBBS, MS, DNB, PhD, Division of Surgery and Interventional Science, University College London, United Kingdom, and colleagues.

Thus, to establish whether delayed second-procedure TARGIT-IORT is noninferior to whole-breast EBRT with regard to local control, Dr Vaidya et al examined whether RT could safely be limited to the tumor bed.

They did so by conducting a parallel study to the March 2000 TARGIT-A trial of 1153 patients with invasive ductal breast carcinoma <3.5 cm being treated with breast conservation. Beginning in 2004, patients whose cancer was excised were randomized to receive EBRT (n = 572; mean age, 63 years) or delayed TARGIT-IORT administered as a second procedure by reopening the lumpectomy wound (n = 581; mean age, 63 years).

The main end points of the study were a noninferiority margin for local recurrence rate of 2.5% at 5 years and long-term survival outcomes; study data were locked for analysis as of July 3, 2019.

Ultimately, 60 (5%) patients had tumors >2 cm or positive nodes, and delayed TARGIT-IORT was not deemed noninferior to EBRT. At complete follow-up, the 5-year local recurrence rates were 3.96% and 1.05% with delayed TARGIT-IORT and EBRT, respectively (difference, 2.91%; upper 90% CI, 4.4%).

When factoring in long-term follow-up (median, 9.0 years), Dr Vaidya et al reported no statistically significant difference in local recurrence-free survival (HR, 0.75; 95% CI, 0.57-1.003; P = .052), mastectomy-free survival (HR, 0.88; 95% CI, 0.65-1.18; P = .38), distant disease-free survival (HR, 1.00; 95% CI, 0.72-1.39; P = .98), or OS (HR, 0.96; 95% CI, 0.68-1.35; P = .80).

“These long-term data show that despite an increase in the number of local recurrences with delayed TARGIT-IORT, there was no statistically significant decrease in mastectomy-free survival, distant disease-free survival, or [OS],” Dr Vaidya and colleagues concluded.—Hina Porcelli

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