3 fraction pencil-beam scanning proton accelerated partial breast irradiation: early provider and patient reported outcomes of a novel regimen

Abstract

Background and purposeTo report dosimetry and early adverse effects, aesthetic, and patient-reported outcomes of a prospective study of 3-fraction pencil-beam scanning (PBS) proton accelerated partial irradiation (APBI).Materials and methodsEligibility included women age ≥ 50 years with estrogen receptor positive (ER+), sentinel lymph node negative invasive or in-situ breast cancer measuring ≤2.5 cm. The prescription was 21.9 Gy (RBE 1.1) in 3 daily fractions to the post-operative tumor bed with a 1 cm expansion. Toxicities were collected using Common Terminology Criteria for Adverse Events (CTCAE) version 4.0, 10-point Linear Analog Scale Assessment, Patient-Reported Outcomes Version of the CTCAE, and the Harvard Breast Cosmesis Scale.ResultsSeventy-six women were treated between 2015 and 2017. The median breast volume receiving 50% of prescription or more was 28%. Median mean heart, mean ipsilateral lung, and maximum skin dose were 0 Gy, 0.1 Gy, and 20.6 Gy, respectively. With a median follow-up of 12 months, no treatment-related toxicity grade ≥ 2 has been observed. Most common grade 1 adverse events were dermatitis (68%) and skin hyperpigmentation (18%). At 12 months, the only persistent toxicities were one patient with grade 1 breast edema and one patient with a grade 1 seroma. 90% of patients reported quality of life as ≥7 out of 10 (0 indicating “as bad as it can be” and 10 indicating “as good as it can be”) and 98% of patients reported excellent or good cosmesis.Conclusion3-fraction PBS proton APBI is well tolerated with low rates of physician and patient reported early adverse effects. Follow-up is ongoing to assess late toxicities and disease control outcomes. Further investigation of this novel adjuvant treatment strategy is warranted.

Particle Therapy for Breast Cancer

“…Similarly, a 100 patient cohort phase II trial was recently reported demonstrating high local control, patient satisfaction, low treatment burden, and minimal dose to the heart and lung [ 65 ]. Finally, a 3-fraction regimen of proton-based APBI, reported good or excellent cosmesis in 95% of patients, but additional study is needed [ 66 ].…”

“…Separate cost analyses may be warranted for additional scenarios in breast cancer radiotherapy, including those with altered fractionation. For instance, partial breast irradiation has historically been offered for carefully-selected elderly patients with favorable tumor characteristics; however, providing a 3-fraction proton-based PBI treatment may also provide cost-effective treatment to a young patient by minimizing secondary malignancies and cardiac risk [ 66 ]. Despite rigorous efforts, a modern, overarching cost-effectiveness analysis incorporating changes in the duration of treatment (e.g., hypofractionation) is still needed.…”

Delivery of Adjuvant Radiation in 5 Days or Less After Lumpectomy for Breast Cancer: A Systematic Review

“…57 Another study evaluated 3 fraction proton APBI in 76 patients, demonstrating feasibility with no grade 2 or greater toxicity and 98% of patients having excellent/good cosmesis, though long-term follow-up was not available. 58 The ultimate EBRT APBI regimen would be a single fraction approach. A prospective study of 50 patients from Washington University evaluated such an approach, with 20 Gy given to the surgical bed (5 Gy at 1 cm).…”

Proton Therapy for Partial Breast Irradiation: Rationale and Considerations

“…The skin dose was purposefully limited to a median maximum dose to 1 cc of the skin of 89% of the prescription dose; the heart and ipsilateral breast doses were also low at 0% and 28% of ipsilateral breast receiving ≥50% of the prescription dose, respectively. Early results have been reported, and at a median follow-up of 12 months, there have been no grade 2 or worse acute or late adverse events reported, and patient-reported cosmesis was good or excellent in 98% of patients [ 35 ].…”

“…While PT dosimetry is superior to other external beam PBI delivery methods, further improvements may be possible with increasing utilization of modern pencil beam scanning PT, which has increased ability to modulate dose to the skin, provide a homogeneous dose distribution, and more effectively minimize dose to nontarget tissue. Importantly, patient-reported quality of life also appears well preserved with PT PBI, with 90% of patients reporting a 7 or better QOL on a scale of 0–10, with 10 being the best QOL in the series from Mayo Clinic, and a patient satisfaction rate of treatment and results of 100% at 24 months in the study from MDACC [ 34 , 35 ].…”