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Risk of lymphedema is greatly increased when a posterior axillary boost of radiation is delivered after breast cancer surgery, researchers at the Fox Chase Cancer reported Wednesday during the 48th annual meeting of the American Society of Therapeutic Radiology and Oncology (ASTRO), being held this week in Philadelphia.
"Lymphedema can be a big problem for our patients," principal investigator Dr. Shelly B. Hayes told meeting attendees. "It's a long-term side effect, lasting for 6 months to as long as 1 or 2 years."
She presented findings for 405 patients with non-metastatic breast cancer at stage T1 or T2 and any number of positive lymph nodes. Patients were treated between 1995-2005 with lumpectomy and axillary lymph node dissection. Patients also received radiation to the breast and supraclavicular lymph nodes with a median dose of 46 Gy, and 45% received an additional dose to the posterior axillary nodes.
Dr. Hayes reported that 27% overall developed lymphedema. The risk of lymphedema was 31% in patients receiving an axillary dose and 23% in those receiving radiation to the supraclavicular nodes only.
Lymphedema severity was not significantly different, regardless of whether an axillary dose was delivered. Lymphedema was mild in 55%, moderate in 34% and severe in 10%.
The number of positive axillary nodes and nodal status were risk factors for the complication, as were older age and a higher body mass index.
Patients with four or more positive nodes were four times more likely to develop lymphedema if they received both supraclavicular and axillary radiation compared with their counterparts who received only supraclavicular radiation, Dr. Hayes reported.
On the other hand, Dr. Hayes said, recurrence rates were lower in patients who received the extra axillary boost than in those who received supraclavicular treatment only.
"This was a retrospective study," Dr. Hayes emphasized in an interview with Reuters Health before her presentation. "It's hard to say that the axillary radiation was causative. Dose didn't fall out as being significant, but most patients received the same dose."
And while cause and effect were not studied, and incidence rates only have been analyzed, Dr. Hayes suggested "people might take pause when considering an extra axillary dose of radiation."