Is prone free breathing better than supine deep inspiration breath-hold for left whole-breast radiotherapy? A dosimetric analysis

Abstract

Purpose The advantage of prone setup compared with supine for left-breast radiotherapy is controversial. We evaluate the dosimetric gain of prone setup and aim to identify predictors of the gain. Methods Left-sided breast cancer patients who had dual computed tomography (CT) planning in prone free breathing (FB) and supine deep inspiration breath-hold (DiBH) were retrospectively identified. Radiation doses to heart, lungs, breasts, and tumor bed were evaluated using the recently developed mean absolute dose deviation (MADD). MADD measures how widely the dose delivered to a structure deviates from a reference dose specified for the structure. A penalty score was computed for every treatment plan as a weighted sum of the MADDs normalized to the breast prescribed dose. Changes in penalty scores when switching from supine to prone were assessed by paired t-tests and by the number of patients with a reduction of the penalty score (i.e., gain). Robust linear regression and fractional polynomials were used to correlate patients’ characteristics and their respective penalty scores. Results Among 116 patients identified with dual CT planning, the prone setup, compared with supine, was associated with a dosimetric gain in 72 (62.1%, 95% CI: 52.6–70.9%). The most significant predictors of a gain with the prone setup were the breast depth prone/supine ratio (>1.6), breast depth difference (>31 mm), prone breast depth (>77 mm), and breast volume (>282 mL). Conclusion Prone compared with supine DiBH was associated with a dosimetric gain in 62.1% of our left-sided breast cancer patients. High pendulousness and moderately large breast predicted for the gain.

Cardiopulmonary-related patient-reported outcomes in a randomized clinical trial of radiation therapy for breast cancer

“…Investing in lung/heart-sparing techniques do yield a benefit. Currently many approaches are available [ 43 ]. The challenge will be to choose the most cost-effective technique applicable to the largest number of patients.…”

Prone versus supine free-breathing for right-sided whole breast radiotherapy

“…Table 4 examined the applicability of the cutoffs previously found significant for the left breast 8 . Indices of pendulousness were not significant, whereas measures related to breast volume were significant: ratio of breast volume over body weight, breast volume proper, and depth of the right breast supine.…”

“… Transposed from Table 3 in: Wang X et al 8 . Reproduced without change according to a Creative Commons Attribution 4.0 International License.…”

“…Treatment was delivered according to patient's preference and according to the best dosimetry. In a comparison with supine setup in deep inspiration breath hold for left breast cancer, chart review showed a dosimetric advantage associated with prone setup in 62.1% of 116 patients 8 . The comparison used a penalty score that weighted the mean absolute dose deviations (MADD) 9 to the heart, the lungs, the breasts, and the tumor bed (MADD and penalty weights are detailed in “ Methods ”).…”

“…It appears opportune to fill in that gap. The present study aims are: Evaluate the dosimetric advantage of a change of treatment position from supine to prone in right whole-breast radiotherapy, advantage defined as the lowest radiation dose to non-target organs (heart, lungs, contralateral breast) while delivering the prescribed dose to tumor bed and ipsilateral breast, quantified using the penalty score previously applied in left breast analyses 8 . Look for predictors of the dosimetric advantage.…”