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TOPLINE:

Prophylactic radiation therapy to the contralateral breast significantly delayed the onset of contralateral breast cancer in carriers of BRCA1/2 pathogenic variants with early breast cancer. The 10-year contralateral breast cancer rates were lower among those who received radiotherapy than among those who did not.

METHODOLOGY:

• Women with germline pathogenic variants in the BRCA1/2 genes have a high risk for contralateral breast cancer.
• This study reported the long-term results of a phase 2 trial that enrolled 162 BRCA1/2 pathogenic variant carriers (mean age, 49.7 years) with unilateral early breast cancer between.
• Participants either received prophylactic radiotherapy to the contralateral breast (intervention group; n = 80) or underwent surveillance (control group; n = 82), with all participants concurrently receiving radiation therapy to the ipsilateral breast.
• The primary endpoint was contralateral breast cancer at 10 years, and secondary endpoints included ipsilateral breast tumor recurrence, other cancers, metastatic breast cancer, and death. The median follow-up duration was 10.4 years.

TAKEAWAY:

• At 10.4 years, 13.8% of patients in the intervention group vs 18.3% in the control group developed contralateral breast cancer (P = .24).
• The median time to contralateral breast cancer was significantly longer in the intervention group than in the control group (90 months vs 40 months; P < .001).
• Ipsilateral breast tumor recurrence was observed in 7.4% of patients (n = 12), with occurrences evenly distributed between both treatment groups (six in each group) at a median of 81 months.
• No significant differences were observed between the two groups regarding the development of other cancers or metastatic breast cancer as well as mortality.

IN PRACTICE:

“This novel approach, albeit controversial, is supported by the findings that highlight the need for a larger international trial,” the authors concluded.

SOURCE:

The study, led by Ella Evron, MD, Oncology, Kaplan Medical Institute, Rehovot, Israel, was published online in JAMA Oncology.

LIMITATIONS:

Higher rates of estrogen receptor positivity and endocrine treatment for the index breast cancer, as well as elective risk-reducing mastectomy, in the control group could have contributed to the lower-than-expected rate of contralateral breast cancer. The incidence of ipsilateral breast tumor recurrence was also lower than expected, which could have affected the findings.

DISCLOSURES:

This trial was funded by the Israel Cancer Association. The authors reported having no relevant conflicts of interest.

This article was created using several editorial tools, including AI, as part of the process. Human editors reviewed this content before publication.