Purpose
To report the 5-year results of a prospective trial of three-dimensional conformal external beam radiotherapy (3D-CRT) to deliver accelerated partial breast irradiation in the prone position (P-APBI).
Methods
Post-menopausal patients with Stage I breast cancer with non palpable <2 cm tumors, negative margins, and negative nodes, positive hormonal receptors, and no extensive intraductal component (EIC) were eligible. The trial was offered only once eligible patients had refused to undergo standard whole-breast radiotherapy. Patients were simulated and treated on a dedicated table for prone set-up. The 3D-CRT delivered was 30 Gy in five 6 Gy/daily fractions over 10 days with port film verification at each treatment. Ipsilateral breast, ipsilateral nodal, contralateral breast, and distant failure (IBF, INF, CBF, DF) were estimated using the cumulative incidence method. Disease-free, overall, and cancer-specific survival (DFS, OS, CSS) were recorded.
Results
One hundred patients accrued to this IRB- approved prospective trial, one with bilateral breast cancer. One patient withdrew consent after simulation and another elected to interrupt radiotherapy after receiving two treatments. Ninety-eight patients are evaluable for toxicity and, in one case, both breasts were treated with PBI. Median patient age was 68 years (range 53–88 years); in 55% the tumor size was <1 cm. All patients had hormonal receptor positive cancers: 87% underwent adjuvant anti-hormonal therapy.
At a median follow-up of 64 months (range, 2–125 months), there was one local recurrence (1% IBF) and one contralateral breast cancer (1% CBF). There were no deaths due to breast cancer by 5 years. Grade 3 late toxicities occurred in 2 patients (1 breast edema, 1 transient breast pain). Cosmesis was rated good/excellent in 89% of patients with at least 36 months follow-up.
Conclusions
Five-year efficacy and toxicity of 3D-CRT to deliver prone-PBI are comparable to other experiences with similar follow-up.
among survivors has been acceptable with no severe (>grade 3) side effects noted. Conclusion: We have been able to successfully deliver a total dose of up to 1800 cGy to the entire bony skeleton with our TMI technique without observing any dose-limiting toxicity among the patients. Further dose-escalation appears feasible, and treatment response is encouraging since the median time to relapse post second ASCT in this high-risk population appears to be consistent with that reported in the literature. We are now in the process of increasing the total dose to 2000 cGy/10fr/bid/5 days.
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