Abstract
Purpose: This study investigated the association between radiation dose and complication rate in patients who underwent breast reconstruction to understand the role of radiation hypofractionated regimen, boost radiation therapy (RT), and RT techniques.Methods: We retrospectively evaluated 75 patients treated with post-mastectomy adjuvant RT for breast cancer in the setting of two-stage prosthetic breast reconstruction. Near maximum radiation dose (Dmax) in the 2 or 0.03 cc of reconstructed breast or overlying breast skin was obtained from dose-volume histograms.Results: Post-RT complications occurred in 22.7% of patients. Receiver operating characteristic analysis showed that all near Dmax parameters were able to predict complication risk, which retained statistical significance after adjusting other variables (odds ratio 1.12 per Gy, 95% confidence interval 1.02–1.23) with positive dose-response relationship. In multiple linear regression model (R2 = 0.92), conventional fractionation (β = 11.7) and 16 fractions in 2.66 Gy regimen (β = 3.9) were the major determinants of near Dmax compared with 15 fractions in 2.66 Gy regimen, followed by utilization of boost RT (β = 3.2). The effect of bolus and dose inhomogeneity seemed minor (P > 0.05). The location of hot spot was not close to the high density metal area of the expander, but close to the surrounding areas of partially deflated expander bag.Conclusions: This study is the first to demonstrate a dose-response relationship between risk of complications and near Dmax, where hypofractionated regimen or boost RT can play an important role. Rigorous RT-quality assurance program and modification of dose constraints could be considered as a critically important component for ongoing trials of hypofractionation. Based on our findings, we initiated a multi-center retrospective study (KROG 18-04) and a prospective study (NCT03523078) to validate our findings.
Highlights
Breast reconstruction provides important psychosocial, cosmetic, and quality of life benefits for women undergoing mastectomy [1, 2], which accounts for approximately more than 60% of mastectomy women in the US [3]
Expander with acellular dermal matrix (ADM) was inserted at the time of mastectomy
There have been outstanding advances in reconstructive procedures and materials, post-mastectomy radiation therapy (RT) remains to have a profound impact on complications related to reconstruction [16]
Summary
Breast reconstruction provides important psychosocial, cosmetic, and quality of life benefits for women undergoing mastectomy [1, 2], which accounts for approximately more than 60% of mastectomy women in the US [3]. As recent evidence has widened the indications of post-mastectomy radiation therapy (RT) to early-stage node-positive breast cancer [4], an increasing number of patients is currently referred for adjuvant RT to the reconstructed breast, which has put treating physicians in a challenging situation. There is substantial evidence from small case series and prospective cohort studies demonstrating that RT significantly increases complications following breast reconstruction regardless of the type of reconstructive surgery and timing of surgery [5, 6]. Breasts reconstructed with implants are known to be more susceptible to RT-related complications compared with breasts reconstructed with autologous tissue [7]. RT to prosthetic breast reconstruction is no longer contraindicated [3, 8]
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