Professor Ian Kunkler

Radiation therapy after breast-conserving surgery may not be necessary in some older patients with HR-positive breast cancer, according to new research presented at the San Antonio Breast Cancer Symposium. Though local recurrences were more common, the lack of radiation therapy had no impact on 10-year survival rates.

“Based on these results, we believe that omission of radiation therapy after breast-conserving surgery should be an option for older patients with localised, HR-positive breast cancer who are receiving adjuvant hormone therapy and meet certain clinico-pathological criteria,” said Professor Ian Kunkler, of Western General Hospital at the University of Edinburgh.

The PRIME II trial included 1,326 patients with non-metastatic HR-positive breast cancer, all of whom were at least 65 years of age. Previous reports from the trial indicated higher rates of local recurrence in those who did not receive radiation therapy, but with no impact on survival, distant metastases, or new breast cancers.

The new report, with 10-year follow-up results on all outcomes, confirmed improved local control with radiation – 9.8% of patients experienced a local recurrence without radiation compared with 0.9% in those who did receive radiation (p=0.00008).

The metastasis-free survival rate was 98.1% in those with no radiation therapy and 96.4% in those with radiation (p=0.28). Recurrence in the opposite breast was found in 1.0% of radiation therapy patients and in 2.2% of those who did not receive radiation.

The overall survival rate was 80.4% without radiation, and 81.0% with radiation, which was not significant. Most deaths in the trial (93.4%) were due to causes other than breast cancer.

“Omission of postoperative radiotherapy is a reasonable option,” Professor Kunkler said, in patients with pT1-2 tumours of less than 3 cm. “There is no evidence that this increases the risk of metastatic disease nor impacts on survival.”

He noted that it still remains important to identify the lowest risk groups in this setting, potentially with genomic signatures that could predict for radiosensitivity.

The decision of whether or not to undergo radiation therapy will involve a variety of patient-specific factors, Professor Kunkler said, and the higher rate of local recurrence may still be an important factor for many people.

“I think it needs to be a multidisciplinary decision,” he said. “Importantly, there is no compromise in terms of mortality, and I think that should be reassuring to providers.”

Disclosure statement: Prof Kunkler reports no conflicts of interest or financial disclosures.