Effect of Supine vs Prone Breast Radiotherapy on Acute Toxic Effects of the Skin Among Women With Large Breast Size

Abstract

IMPORTANCEWomen with large breast size treated with adjuvant breast radiotherapy (RT) have a high rate of acute toxic effects of the skin. Breast RT in the prone position is one strategy that may decrease these toxic effects.OBJECTIVE To determine if breast RT in the prone position reduces acute toxic effects of the skin when compared with treatment in the supine position.DESIGN, SETTING, AND PARTICIPANTS This phase 3, multicenter, single-blind randomized clinical trial accrued patients from 5 centers across Canada from April 2013 to March 2018 to compare acute toxic effects of breast RT for women with large breast size (bra band Ն40 in and/or ՆD cup) in the prone vs supine positions. A total of 378 patients were referred for adjuvant RT and underwent randomization. Seven patients randomized to supine position were excluded (5 declined treatment and 2 withdrew consent), and 14 patients randomized to prone position were excluded (4 declined treatment, 3 had unacceptable cardiac dose, and 7 were unable to tolerate being prone). Data were analyzed from April 2019 through September 2020. INTERVENTIONS Patients were randomized to RT in the supine or prone position. From April 2013 until June 2016, all patients (n = 167) received 50 Gy in 25 fractions (extended fractionation) with or without boost (range, 10-16 Gy). After trial amendment in June 2016, the majority of patients (177 of 190 [93.2%]) received the hypofractionation regimen of 42.5 Gy in 16 fractions. MAIN OUTCOMES AND MEASURES Main outcome was moist desquamation (desquamation).RESULTS Of the 357 women (mean [SD] age, 61 [9.9] years) included in the analysis, 182 (51.0%) were treated in the supine position and 175 (49.0%) in prone. There was statistically significantly more desquamation in patients treated in the supine position compared with prone (72 of 182 [39.6%] patients vs 47 of 175 [26.9%] patients; OR, 1.78; 95% CI, 1.24-2.56; P = .002), which was confirmed on multivariable analysis (OR, 1.99; 95% CI, 1.48-2.66; P < .001), along with other independent factors: use of boost (OR, 2.71; 95% CI, 1.95-3.77; P < .001), extended fractionation (OR, 2.85; 95% CI, 1.41-5.79; P = .004), and bra size (OR, 2.56; 95% CI, 1.50-4.37; P < .001).CONCLUSIONS AND RELEVANCE This randomized clinical trial confirms that treatment in the prone position decreases desquamation in women with large breast size receiving adjuvant RT. It also shows increased toxic effects using an RT boost and conventional fractionation.

Validation of a Patient-Reported Outcome Measure for Moist Desquamation among Breast Radiotherapy Patients

“…A previous BC Cancer randomized trial to investigate potential advantages of silver leaf nylon dressing to promote wound healing found that 38% of breast RT patients with D cup or larger, or with skin folds 1 cm or deeper, experienced MD at our institution [ 11 ]. This is consistent with a recent randomized controlled trial of prone breast RT for a similar patient population [ 8 ]. Skin-sparing techniques such as partial breast irradiation and hypo-fractionated breast RT treatment schedules have reported lower rates of acute skin toxicity in intact breast RT [ 8 , 12 , 13 ].…”

“…This is consistent with a recent randomized controlled trial of prone breast RT for a similar patient population [ 8 ]. Skin-sparing techniques such as partial breast irradiation and hypo-fractionated breast RT treatment schedules have reported lower rates of acute skin toxicity in intact breast RT [ 8 , 12 , 13 ]. Other interventions such as a novel carbon-fiber breast support to remove infra-mammary folds (IMFs) are also under investigation for reduction in MD rates [ 14 ].…”

“…Overall rates of MD in a given setting will depend heavily on how the patient population is distributed with respect to various body types. This may explain some of the variation in reported MD rates from study to study [ 8 , 13 , 22 ].…”

“…As well, there are other factors described in the literature, but not analyzed in our study, that have been reported to affect the incidence of MD. These include the location of the hot spot in the IMF during RT planning [ 24 ], the prone position [ 8 ], and the use of a custom-fit bra or a breast positioning device [ 25 ]. The choice of RT technique is also known to impact breast RT outcomes, including MD.…”

“…Up to 40% of women receiving adjuvant RT are expected to develop some moist desquamation (MD), a painful and worrisome radiation skin reaction observed when radiation dose exceeds the survival tolerance of cells in the basal layer [ 8 , 9 , 10 ]. A previous BC Cancer randomized trial to investigate potential advantages of silver leaf nylon dressing to promote wound healing found that 38% of breast RT patients with D cup or larger, or with skin folds 1 cm or deeper, experienced MD at our institution [ 11 ].…”