Abstract
Introduction: Accelerated partial breast irradiation (APBI) with protons results in a very different acute effect profile than standard whole breast irradiation. We reviewed our initial experience with proton APBI and felt that a detailed description of these effects were needed to permit a common tool to compare experience with this developing technology. Methods: Sixty sequential patients treated with proton APBI on a prospective protocol were evaluated and 43 patients with a minimum six-month follow-up underwent detailed photographic and radiologic analysis. The tumorectomy cavity plus an additional 1.5 cm clinical target volume (CTV) was treated with two or three passively-scattered proton beams to a dose of 34 Gy in 10 fractions in one week. Photographs were taken at the end of radiation, at two weeks, six weeks, and every six months thereafter. Mammography was obtained at six months after radiation and annually thereafter. All visual changes were categorized using the smallest meaningful gradations in findings and are demonstrated herein. All treatment-related mammographic findings are reported. Findings: Visual and mammographic findings showed a clear time-dependent relationship and significant variation between individuals. Peak skin reaction occurred at two to six weeks after completion of therapy. At two weeks most patients had either no visible effects and patchy erythema involving <50% of the treated skin (60%). At six weeks most patients had either patchy erythema involving <50% of the overlying skin (33%) or patchy erythema involving >50% of the treated skin (28%). Only one patient developed any moist desquamation. At six months most patients had no visible skin changes (57%) or a small, circular area of mild hyperpigmentation (33%). Mammographic changes seen at six months were regional skin thickening (40%), residual seroma (14%), localized retraction (26%), and fat necrosis (2%). A subcategorized variant on the CTCAE 4.0 was developed to foster granular recording of these findings.
Highlights
Accelerated partial breast irradiation (APBI) with protons results in a very different acute effect profile than standard whole breast irradiation
According to the US National Cancer Institute database, amongst women with stage 0–II breast cancer treated with breast conserving surgery and radiotherapy from 2003–2010, 10.3% received accelerated partial breast irradiation (APBI), mainly brachytherapy
Our objective was to perform a detailed description of evolving acute skin toxicity in patients with early-stage breast cancer treated with proton APBI and to correlate skin changes following radiotherapy with mammographic findings at six months
Summary
Accelerated partial breast irradiation (APBI) with protons results in a very different acute effect profile than standard whole breast irradiation. Methods: Sixty sequential patients treated with proton APBI on a prospective protocol were evaluated and 43 patients with a minimum six-month follow-up underwent detailed photographic and radiologic analysis. According to the US National Cancer Institute database, amongst women with stage 0–II breast cancer treated with breast conserving surgery and radiotherapy from 2003–2010, 10.3% received accelerated partial breast irradiation (APBI), mainly brachytherapy. Cancers 2018, 10, 111 radiation dose in a 1–2 week interval, while the more classic whole-breast irradiation schedules take 4–6 weeks [3,4]. Amongst the most commonly utilized are brachytherapy, intensity-modulated radiation therapy (IMRT), and 3D-conformal external beam APBI with photons/electrons [1]. More recently proton APBI was introduced with the advantage of being non-invasive while offering high dose conformality and homogeneity
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