Targeted Intraoperative Radiotherapy vs External Beam Radiotherapy in Patients with Breast Cancer

There was no statistically significant decrease in mastectomy-free survival, distant disease-free survival, or overall survival with delayed targeted intraoperative radiotherapy despite an increase in the number of local recurrences, according to a recent study published in JAMA Oncology.

More, delayed second-procedure single-dose targeted intraoperative radiotherapy via reopening the lumpectomy wound for patients with early breast cancer saw similar long-term mastectomy-free and overall survival data compared with external beam radiotherapy.

“Based on the randomized evidence of immediate targeted intraoperative radiotherapy, which has been shown to be an effective alternative to external beam radiotherapy, it is clear that the preferred timing of using targeted intraoperative radiotherapy is immediately-during the initial surgical excision of breast cancer,” wrote the researchers.

The researchers enrolled 1153 patients aged 45 years or older with invasive ductal breast carcinoma into this randomized noninferiority trial. Of that group, 581 patients were randomized to receive targeted intraoperative radiotherapy and 572 patients were randomized to receive external beam radiotherapy.

The results suggested that delayed targeted intraoperative radiotherapy was not noninferior to external beam radiotherapy, with local recurrence rates at 5-year complete follow-up being: delayed targeted intraoperative radiotherapy vs external beam radiotherapy (23/581 [3.96%] vs 6/572 [1.05%], respectively; difference, 2.91%; upper 90% CI, 4.4%).

However, for long-term follow-up (median [IQR], 9.0 [7.5-10.5] years), there was 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 overall survival (HR, 0.96; 95% CI, 0.68-1.35; P = .80).

“When considering treatments for patients with early breast cancer, local recurrence has been given great importance because of the perceived risk of consequent mastectomy, the danger of distant disease, and the potentially lower survival,” wrote the researchers. “The long-term data show that there was no impairment of mastectomy-free survival, distant disease-free survival, or overall survival, up to 12 years from randomization.”

The researchers had limits to their study, including a lack of anticipation for change in the surgical practice in later years. Rather than leaving a cavity, the researchers explained that the tumor bed was approximated after tumor excision. More, adequate dose may not have reached the tumor bed because of the rapid attenuation of dose. Finally, the researchers speculated that any additional surgical trauma from a necessary second procedure in the case of delayed targeted intraoperative radiotherapy could stimulate residual cancer cells.

Moving forward, the researchers hope the data collected in this study can help push the field forward by acting to inform discussions between patients and clinicians on postoperative courses. Further patient preference research is required to better assist with these discussions.

“When immediate targeted intraoperative radiotherapy 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 external beam radiotherapy,” wrote the researchers.

Reference:

Vaidya JS, Bulsara M, Saunders C, et al. Effect of Delayed Targeted Intraoperative Radiotherapy vs Whole-Breast Radiotherapy on Local Recurrence and Survival. JAMA Oncol. doi:10.1001/jamaoncol.2020.0249.