medwireNews: A phase 3 trial has failed to demonstrate the noninferiority of delayed targeted intraoperative radiotherapy (TARGIT-IORT) to whole-breast external beam radiotherapy (EBRT) in terms of local control at 5 years in patients with early-stage breast cancer, but other long-term outcomes were comparable.
Noting that the previously published TARGIT-A trial showed the noninferiority of TARGIT-IORT given during the same operation immediately after lumpectomy by inserting the radiotherapy applicator directly into the open wound, Jayant Vaidya (University College London, UK) and colleagues say: “[I]t is clear that the preferred timing of using TARGIT-IORT is immediately–during the initial surgical excision of breast cancer.
“However, when immediate TARGIT-IORT has not been possible, the long-term data presented in this article may help inform discussions by clinicians and patients who wish to avoid a prolonged postoperative course of EBRT.”
Speaking to medwireNews, Vaidya pointed out that “these results could be of special relevance during the current COVID-19 pandemic.”
Among the 581 patients with invasive ductal breast carcinoma (≤3.5 cm) who were randomly assigned to receive delayed second-procedure TARGIT-IORT by re-opening the wound – at a median of 37 days after the original procedure – 3.96% had a local recurrence at 5 years.
By comparison, the rate among the 572 patients who received EBRT was 1.05%, giving a between-group difference of 2.91%, with an upper 90% confidence interval limit of 4.40%. This crossed the “stringent” prespecified margin of 2.50%, and therefore the noninferiority of delayed TARGET-IORT was not proven, say the researchers in JAMA Oncology.
Nevertheless, after a median follow-up of 9 years, there was no statistically significant difference between the treatment groups with respect to local recurrence-free survival. And other outcomes, such as mastectomy-free survival, distant disease-free survival, breast cancer-specific survival, and overall survival were similarly comparable.
Vaidya commented: “From the patient’s perspective, the standard treatment for local recurrence after lumpectomy and whole-breast radiotherapy is mastectomy. However, patients who develop a local recurrence after TARGIT-IORT can still have a lumpectomy. So, the good news from this study is that even though the local recurrence was slightly higher, by 2.9%, patients could still preserve their breast.”
The investigators notes that TARGIT-IORT has been shown to be superior to EBRT in terms of patient-reported outcomes, such as breast pain and cosmesis, and quality of life, and patient preference studies have shown that many patients prefer TARGIT-IORT “even in the face of a hypothetically higher local recurrence risk.”
The current data “may mitigate some of the patient concerns, and results of further patient preference research would help these discussions,” they add.
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