Older women with early breast cancer may be able to avoid radiation after surgery
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The omission of radiation therapy after breast-conserving surgery did not affect survival among certain older women with early breast cancer, according to results presented at the virtual San Antonio Breast Cancer Symposium.
Radiation therapy reduced the rate of ipsilateral breast tumor recurrence among women aged 65 years or older with hormone receptor-positive disease who underwent wide local excision and were receiving adjuvant hormonal therapy.
However, radiation therapy receipt did not affect rates of distant metastases, contralateral breast cancer or OS, 10-year data from the randomized phase 3 PRIME II trial showed.
“Based on these results, we believe that omission of radiation therapy after breast-conserving surgery should be an option for older patients with localized, hormone receptor-positive breast cancer who are receiving adjuvant hormone therapy and meet certain clinic-pathological criteria,” Ian H. Kunkler, FRCPE, professor of clinical oncology at Western General Hospital at University of Edinburgh, said in a press release.
More than half of patients diagnosed with breast cancer in developed nations are aged older than 65 years. Although breast cancers in this population tend to be less aggressive, treatment often includes breast-conserving surgery followed by whole-breast radiation therapy.
However, limited level one evidence exists about the impact of loco-regional radiotherapy on long-term outcomes among older patients who undergo breast-conserving surgery and receive appropriate systemic therapy, according to study background.
“We were interested in determining whether older patients with low-risk breast cancer could be spared radiation therapy,” Kunkler said.
Kunkler and colleagues conducted the international PRIME II study to assess whether older women with low-risk breast cancer could safely be spared radiation therapy.
Investigators recruited 1,326 women aged 65 years or older from April 2003 through December 2009. Eligible women had T1 or T2, N0, M0 hormone receptor-positive disease (tumors < 3 cm).
All women had undergone breast-conserving surgery with clear excision margins (minimum 1 mm), were axillary node negative and were receiving adjuvant hormone therapy.
Women could have lymphovascular invasion or grade 3 tumors but not both.
Researchers randomly assigned 658 women to receive whole-breast radiotherapy. The other 668 received no radiation.
Ipsilateral breast tumor recurrence served as the primary endpoint. Secondary endpoints included regional recurrence, contralateral breast cancer, distant metastases and OS.
Five-year results showed a higher rate of local recurrence among women who did not receive radiation therapy, but no statistically significant differences between treatment groups in OS, distant metastases or new breast cancers.
During the symposium, Kunkler presented updated data based on median follow-up of 7.3 years.
Updated results continued to show a significantly higher local recurrence rate among women who did not receive radiation therapy (9.8% vs. 0.9%). Researchers calculated an HR for ipsilateral breast tumor recurrence of 0.12 (95% CI, 0.05-0.31) favoring those who received radiotherapy.
Results showed a significant increase in regional recurrence among women who did not receive radiation (2.3% vs. 0.5%; P = .014). However, researchers reported no significant difference in rates of distant metastases (1.4% vs. 3.6%) or contralateral breast cancer (1% vs. 2.2%) between the no-radiation and radiation groups.
A comparable percentage of women in the no-radiation and radiation groups remained alive at 10 years (80.4% vs. 81%), with most deaths in each group (90.9% in no-radiation group vs. 96.2% in radiation group) due to causes other than breast cancer.
Researchers acknowledged the low number of patients with grade 3 tumors limit the applicability of these results to patients with high-grade tumors or those whose tumors are larger than 3 cm. In addition, the fact they did not collect data about comorbidities or adherence to adjuvant hormone therapy served as a limitation.
Perspective
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Stephanie Bernik, MD, FACS
The findings in this study are provocative. Although the authors highlight the survival as being equivalent in the group that avoided radiation compared with the group that received standard radiation, they minimize the negative effects that come along with an increased recurrence rate.
When a woman has a recurrence, she is faced with additional treatment that may include chemotherapy, more aggressive surgery — such as a mastectomy — and the emotional toll that a cancer diagnosis brings with it. These are important facts that need to be taken into account when deciding whether to omit treatment.
Certainly, if a woman has less than a 5-year projected survival, evidence that skipping radiation may not affect long-term survival is useful. However, for healthier women, applying these results to real-life situations needs to be done with caution. When only looking at survival, we neglect to consider that some of these women may develop metastatic disease after recurrence and ultimately may succumb to the disease.
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Kunkler IH, et al. Abstract GS2-03. Presented at: San Antonio Breast Cancer Symposium (virtual meeting); Dec. 8-11, 2020.
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