AMSTERDAM – Modifying the standard radiation dosage to women with early-stage breast cancer so that the tumor-bed dosage remained the same but eliminated the dosage delivered to surrounding breast tissue led to similar 5-year efficacy and reduced adverse effects in a multicenter U.K. trial that involved more than 2,000 patients.
“Partial-breast radiotherapy was noninferior to whole-breast radiotherpy for reducing local recurrences and reduced the severity of overall breast appearance and breast hardness,” Dr. Charlotte Coles said at the European Breast Cancer Congress. “I consider this practice changing,” concluded Dr. Coles of Cambridge (England) University Hospitals.
Mitchel L. Zoler/Frontline Medical News
Dr. Charlotte Coles
While some experts at the meeting agreed with Dr. Coles’ assessment of the findings, others took a more skeptical view, focusing on the median follow-up of just 5 years.
“There is still some question about the long-term results for local recurrence rates,” said Dr. Robert Mansel, professor of surgical oncology at Cardiff (Wales) University. In addition, “the rationale for doing this is to reduce side effects to the whole breast, but the results showed little difference in side effects” between women who received the standard radiation dosage and those who received a reduced dosage, “so the rationale for doing this is not quite there,” said Dr. Mansel, the session’s designated discussant.
The Intensity Modulated Partial Breast Radiotherapy for Women with Early Breast Cancer (IMPORT LOW) trial enrolled 2,018 patients with early breast cancer at 30 U.K. centers during 2007-2010. Patients underwent breast conservation surgery and were at least 50 years old, had a tumor of 3 cm or less, had an invasive and unifocal adenocarcinoma that was grade I, II, or III, and had lymph nodes that were either negative or had micrometastases (pN0 or pN1). The trial randomized these women to either standard, whole-breast radiation with 40 gray, a reduced-dosage regimen that delivered 40 gray to the tumor bed but 36 gray to the rest of the breast, or a partial regimen that delivered 40 gray to the tumor bed and no radiation at all to the rest of the ipsilateral breast. All three regimens were administered as 15 fractions.
Mitchel L. Zoler/Frontline Medical News
Dr. Robert Mansel
After a median follow-up of 71 months, the 674 women randomized to the reduced regimen had a 26% reduction in their absolute local recurrence rate compared with the 674 whole-breast controls. The 670 women randomized to the partial regimen had an absolute reduction of 39%. Both of these relative reductions were statistically significant. These efficacy results also met the study’s prespecified primary endpoint for noninferiority for controlling local recurrences in the ipsilateral breast, Dr. Coles reported.
For the study’s secondary endpoints of various measures of adverse effects to the normal breast tissue, the partial-dosage regimen led to a statistically significant reduction in patient assessment of changed breast appearance (P = .005) and a reduced rate of patient perception of increased breast firmness (P = .001). The adverse-effects endpoints also showed a significant reduction with the partial regimen in physician assessment of breast edema (P = .0053). The overall rate of patients free of any adverse effect in their normal breast tissue after 5 years was 72% in the control patients, 79% in those who received the reduced-dose regimen (P = .042), and 81% in those who received the partial dose (P = .004).
An expert panel is scheduled to review new evidence on breast radiotherapy later in March, and these new data may produce a change in the recommended irradiation protocol, Dr. Coles said.
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