Nick Mulcahy

September 18, 2014

SAN FRANCISCO ― Radiation therapy (RT) did not increase the incidence of lymphedema in patients with node-negative breast cancer who underwent breast-conserving therapy, according to a secondary analysis of a large clinical trial.

"There is no evidence to suggest a detrimental impact" of RT to the breast or chest wall on the risk for lymphedema, said study lead author Susan McCloskey, MD, of the University of California, Los Angeles.

She spoke at a press conference here at the American Society for Radiation Oncology (ASTRO) 56th Annual Meeting.

"These results provide much needed reassurance to breast cancer patients regarding the impact of radiation therapy on lymphedema risk," she said in a statement.

The new results "argue convincingly” that RT does not contribute to lymphedema risk, Dr. McCloskey stated.

Lymphedema is "feared" by patients, she commented.

RT to the whole breast could theoretically cause "collateral damage" to the nearby axillary lymph nodes, which could result in lymphedema, she explained. But surgery could also increase the risk, and it has been "difficult to separate out the independent effects of surgery and radiation therapy" on lymphedema.

But that separation of RT and surgery is exactly what the study authors achieved by using data from the massive National Surgical Adjuvant Breast and Bowel Project (NSABP) B-32 trial.

NSABP B-32 was a randomized trial in which most ― but not all ― patients received both surgery and RT as part of breast conservation therapy. The fact that some of the participants did not receive RT enabled a comparison with those who received RT with regard to the associated risk for the adverse event of lymphedema.

Study Data on Lymphedema

NSABP B-32 actually focused on another aspect of treating these patients ― the management of the axillary lymph nodes. Specifically, the trial compared sentinel node biopsy (SNB) and SNB + axillary lymph node dissection (ALND) among nearly 6000 women with clinically node-negative disease.

The original study results indicated, not surprisingly, that the more invasive combination of SNB + ALND was associated with a significantly greater risk for lymphedema.

In the new study, the authors focused on 3916 women in NSABP B-32 who had undergone lymphedema assessments before and after treatment (baseline and every 6 months up to 36 months).

Importantly, all of these women who underwent assessments had received breast surgery, but not all had received radiation. Specifically, 82.2% (3220) received RT, and 17.2% (674) did not.

Dr. McCloskey and colleagues report that there was no statistically significant difference in the incidence of lymphedema among those who received RT and those who did not.

Another expert was impressed by the findings.

"The evidence suggests that conventional radiation therapy doesn't add to the risk of lymphedema," said Tracy Balboni, MD, of the Dana-Farber/Harvard Cancer Center in Boston, Massachusetts. She moderated the press conference at which Dr. McCloskey spoke.

Dr. Balboni further commented that the new findings add to the evidence base and helps clinicians "feel assured" that RT will not reduce breast cancer patients' quality of life.

The authors reported the specific lymphedema findings (using both objective and subjective measures) in a somewhat complicated breakdown of data, in which data on RT or lack of RT are reported by the 2 different approaches to the management of axillary lymph nodes, SNB+ALND and SNB alone, at a follow-up of 36 months.

Table 1. Women Who Underwent Both SNB+ALND

Follow-up Radiation Measured Swelling >10% P-value
36 months Yes 12.4% P = .09
  No 16.7%  

 

At 36 months in this SNB+ALND group, bothersome swelling (subjective lymphedema) was reported by 7.4% of women who received RT compared with 8.8% who did not receive RT (P = .78).

Table 2. Women Who Underwent SNB Only

Follow-up Radiation Measured Swelling P-value
36 months Yes 7.4% P = .13
  No 4.5%  

 

Finally, at 36 months in the SNB-only group, bothersome arm swelling was reported by 3.2% after RT compared with 4.8% without RT (P = .47).

Dr. McCloskey said that the "lack of agreement" between the objective and subjective measures of arm swelling was "interesting" and was proof of a need for more research in this area.

The study was funded in part by an ASTRO junior faculty career research training award. The authors report no relevant financial relationships.

American Society for Radiation Oncology (ASTRO) 56th Annual Meeting: Abstract 1463. Presented September 14.

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