Dr. Danny Vesprini of Sunnybrook Health Sciences Centre in Toronto and colleagues at five cancer centers in Canada randomly assigned 357 women with large breasts (bra band at least 40 inches and/or at least a D cup) to receive radiation therapy in either the supine or prone position. From April 2013 until June 2016, 167 patients received a prescription dose of 50 Gy in 25 fractions (extended fractionation) with or without a boost (range, 10-16 Gy in 4-8 fractions). In June 2016, to improve trial accrual, the protocol was amended to allow a hypofractionated regimen of 42.5 Gy in 16 fractions; most of the remaining 190 patients received this regimen.
There were no differences between the groups in age, body mass index, bra size, delivery of boost, use of hypofractionation, or use of chemotherapy, according to a report in JAMA Oncology.
The proportion of women who experienced skin desquamation was significantly lower in the prone group (26.9% vs 39.6%; P=0.002), as was the proportion with grade 3 desquamation (8% vs 15.4%; P<0.001).
On multivariable analysis, supine position, bra size, boost, and extended fractionation remained significantly associated with desquamation.
Among patients treated with extended fractionation, the prone position was associated with a lower rate of toxic effects compared with the supine position when evaluating desquamation occurring anywhere in the breast (35.2% vs 51.1%; P<0.001) and with lower rates of grade 3 desquamation (10.2% vs 23.9%; P<0.001) and pain (5.7% vs 13.0%; P<0.001).
Regardless of position, extended fractionation compared to hypofractionation resulted in more desquamation occurring anywhere in the breast (43.3% vs 23.2%; P<0.001), grade 3 desquamation (17.2% vs 6.3%; P=0.001), and pain (9.4% vs 3.4%; P=0.04).
In the supine position, extended fractionation vs hypofractionation was associated with increased desquamation anywhere in the breast (51.1% vs 27.8%; P=0.02) and grade 3 desquamation (23.9% vs 6.7%; P<0.001). In the prone position, extended fractionation was again tied to higher rates of desquamation anywhere in the breast (35.2%, vs 18.4% with hypofractionation; P<0.001) and grade 3 desquamation (10.2% vs 5.7%; P=0.03).
Among those who received the hypofractionated regimen, overall rates of toxic effects were lower in both arms, with no statistically significant difference in any outcome.
There were no differences between the two arms in quality of life (QOL) as measured by the global health status, breast symptom, or pain scales of the European Organization for Research and Treatment of Cancer core QOL questionnaire and breast cancer module. QOL decreased from baseline to end of treatment and then improved after 6 to 8 weeks, although it didn't return to baseline.
In an editorial, Dr. Dean A. Shumway from the Mayo Clinic in Rochester, Minnesota and Dr. Katelyn M. Atkins from Cedars-Sinai Medical Center in Los Angeles said prone positioning "represents an additional method for improving the toxicity profile of whole-breast radiotherapy by decreasing excess lung exposure and improving dose homogeneity, which may particularly benefit women with large and/or pendulous breasts who typically have a higher risk of moist desquamation."
They caution, however, that for some patients with large breast size and left-sided breast cancer, radiation exposure of the heart may potentially be higher in the prone position. "Prone radiotherapy appears to be an excellent option for patients with large breast size and right sided breast cancer, and may benefit many women with left-sided breast cancer with large breast size if acceptable cardiac avoidance is feasible," they conclude.
SOURCE: https://bit.ly/3mErgES and https://bit.ly/3zA6wWG JAMA Oncology, online May 26, 2022.
By Patricia A. Sheiner MD
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