Nonetheless, “Overall survival did not differ between the groups, with about the same numbers of deaths from breast cancer and other causes,” according to the report in The Lancet Oncology online November 11.
Dr. Umberto Veronesi, at the European Institute of Oncology in Milan, and colleagues explain that replacing multiple postop radiation sessions with a single radiation dose during surgery has advantages in terms of convenience and avoidance of skin damage. However, the ability of intraoperative radiotherapy to control recurrence required confirmation.
To that end, the team conducted a trial in which 1305 women with early breast cancer suitable for breast-conserving surgery were randomized to receive postoperative whole-breast external RT (50 Gy in 25 fractions) or intraoperative electron RT (one dose of 21 Gy) delivered to the tumor bed by a dedicated linear accelerator.
Median follow-up was 5.8 years. The 5-year ipsilateral breast tumor recurrence rate was 4.4% in the intraoperative RT group compared with 0.4% in the external RT group – a significant difference with a hazard ratio of 9.3.
Five-year survival rates in the two arms were almost identical at 96.8% and 96.9%, respectively, the investigators report.
Furthermore, there were fewer skin side effects with intraoperative RT than with external RT, Dr. Veronesi and colleagues found.
Overall, they conclude, “Intraoperative radiotherapy should be part of discussions to decide a personalised treatment regimen because it offers the advantage to patients of not having to attend a radiotherapy centre every day for many weeks, and has about the same overall survival as external radiotherapy; however, these advantages must be weighed against the possibility of an increased risk of local recurrence.”
A related editorial discusses these results and those from a trial comparing intraoperative radiation using an x-ray source versus whole-breast irradiation, in which local recurrence rates were 3.3% versus 1.3%, respectively.
These data, conclude Drs. David Azria and Claire Lemanski, at the Institut du Cancer Montpellier, France, “reinforce our conviction that intraoperative radiotherapy during breast-conserving surgery is a reliable alternative to conventional postoperative fractionated irradiation, but only in a carefully selected population at low risk of local recurrence.”