RESUMEN
Purpose: Accelerated partial breast irradiation (APBI) after breast-conserving surgery offers a well-tolerated adjuvant radiation therapy option for patients with breast cancer. We sought to describe patient-reported acute toxicity as a function of salient dosimetric parameters during and after an APBI regimen of 40 Gy in 10 once-daily fractions. Methods and Materials: From June 2019 to July 2020, patients undergoing APBI were assigned a weekly, response-adapted, patient reported outcomes-common terminology criteria for adverse events-based acute toxicity assessment. Patients reported acute toxicity during treatment and for up to 8 weeks after treatment. Dosimetric treatment parameters were collected. Descriptive statistics and univariable analyses were used to summarize patient-reported outcomes and their correlation to corresponding dosimetric measures, respectively. Results: Overall, 55 patients who received APBI completed a total of 351 assessments. Median planning target volume was 210 cc (range, 64-580 cc), and median planning target volume:ipsilateral breast volume ratio was 0.17 (range, 0.05-0.44). Overall, 22% of patients reported moderate breast enlargement and 27% reported maximum skin toxicity as severe or very severe. Furthermore, 35% of patients reported fatigue, and 44% of patients reported pain in the radiated area as moderate to very severe. Median time to first report of any moderate to very severe symptom was 10 days (interquartile range, 6-27 days). By 8 weeks after APBI, most patients reported resolution of symptoms, with 16% reporting residual moderate symptoms. Upon univariable analysis, none of the ascertained salient dosimetric parameters were associated with maximum symptoms or with the presence of moderate to very severe toxicity. Conclusions: Weekly assessments during and after APBI showed that patients experienced moderate to very severe toxicities, most commonly skin toxicity, but that these typically resolved by 8 weeks after radiation therapy. More comprehensive evaluations among larger cohorts are warranted to define the precise dosimetric parameters that correspond to outcomes of interest.
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BACKGROUND: Postmastectomy proton radiotherapy improves normal tissue sparing in comparison to photon-based approaches. Several studies have reported dosimetry comparison and tolerable acute toxicity profile with limited follow-up. We report our institutional experience of postmastectomy proton radiation including clinical efficacy and toxicities. METHODS: From December 2013 to February 2015, 42 consecutive patients who received mastectomy for non-metastatic breast cancer were treated with adjuvant chest wall and regional nodal proton therapy at a single proton center. 3D conformal uniform scanning with en face matching fields was used. RESULTS: The median follow-up among patients was 35â¯months (range 1-55â¯months). There was one local failure, zero regional nodal failure, and six distant failures. The 3-year rate of locoregional disease-free survival was 96.3%, metastasis-free survival was 84.1%, and overall survival was 97.2%. The only local failure event occurred on the chest wall within the radiation field, approximately 2.5â¯years after the completion of radiation. Skin dermatitis, fatigue, and esophagitis were the most common acute toxicity. All patients developed grade 1 or 2 acute skin toxicity and there was no grade 3 or 4 acute skin toxicity. Proton radiation is able to achieve excellent target coverage with median PTV V95 over 95% and heart sparing with median mean heart dose less than 1â¯Gy (RBE). CONCLUSION: With close to three years of median follow-up, post-mastectomy proton radiation has shown excellent locoregional control rates and favorable toxicity profile. Long-term adverse effect of heart-sparing radiation will require longer follow-up time and randomized clinical trials.