Not all breast cancer needs radiation


Older women with low-risk breast cancer who skipped radiation therapy saw small impact on recurrence risk and no effect on survival, a randomized trial showed.

The 5-year rate of local recurrence was low either way, 1.3% with radiation and 4.1% without it (P=0.002), Ian Kunkler, MD, of the University of Edinburgh, and colleagues found in the PRIME II trial.

The overall survival rate was 94% in both groups at 5 years, they reported here at the San Antonio Breast Cancer Symposium.

"When I was in my training 40 years ago, we were in the era of more is better ... more surgery, more radiation, more chemotherapy," commented conference co-chair C. Kent Osborne, MD. "It is turning out as we've evolved over the last 3 decades, that is not the case. We are now in a transition."

One reason is the CALGB 9343 trial suggested minimal risk from avoiding radiation therapy in early-stage breast cancer in patients ages 70 and older. Ten-year follow-up from the trial showed an absolute 6% to 7% difference in local recurrence with radiation and tamoxifen compared with tamoxifen alone.

That has had some impact on practice, but the new results indicating even less difference between groups in a broader age group are likely to further shift practice, Kunkler suggested.

"The absolute benefit is smaller, and I think that may well be enough to change practice," he told reporters at a press conference.

It's almost to the point where radiotherapy can be called overtreatment for low-risk breast cancer among older women, he argued at the press conference.

"Now the local recurrence rates across a whole group of patients managed by breast conserving therapy and radiotherapy are around 2% to 3%, probably down from 5% 10 years ago," he noted. "So the local recurrence rates that we are seeing with the omission of radiotherapy in the low-risk group are of a similar order of magnitude."

"Therefore, I think it is a matter of discussion between the patient and the physician as to whether that very modest benefit is worth the potential risks of complication of radiotherapy and the burden of undergoing treatment," he added, noting, "Older patients find radiation therapy very burdensome."

However, estrogen receptor (ER) status appeared to be a key determinant.

It was the only significant predictor of local recurrence aside from receipt of radiation in the multivariate analysis, with a hazard ratio of 2.84 (P=0.2).

Local recurrence rates with high ER, defined by a score of 7 to 8, were 3.2% without radiation versus 0.8% with it (P=0.003).

But women with low ER, defined by a score of 2 to 6, had an 11.1% rate of local recurrence without radiation therapy compared with none treated with radiation.

The small proportion that express ER but in low levels are more likely to be aggressive, Kunkler pointed out. He suggested that skipping radiation likely isn't a good idea for such women.

But relatively few women fit in that group, only 117 of the 1,326 women in the trial.

"The older you are, the more likely you are to have high ER," Osborne explained.

PRIME II randomized women ages 65 and older (average 70) with clear margins in breast conserving surgery for a HR-positive breast cancer of 3 cm or less in size to whole breast irradiation (40 to 50 Gy in 15 to 25 fractions) along with their adjuvant endocrine therapy.

Node involvement, prior in situ or invasive carcinoma in either breast or other sites in the prior 5 years, and grade 3 breast cancer with lymphatic or vascular invasion were exclusion criteria.

The study population is likely representative of up to 70% of breast cancer patients 65 and older, which accounts for about half of early breast cancers, Kunkler told MedPage Today at the press conference.

"So I think the implications of this study will have broad generalizability to a large and growing number of patients," he said.


Source: MedPage Today:

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