Abstract
BackgroundLocal recurrences after breast conserving treatment are mainly close to the original tumor site, and as such shorter fractionation strategies focused on and nearest mammary gland, i.e. accelerated partial breast irradiation (APBI), have been developed. Stereotactic APBI has been attempted, although there is little experience using CyberKnife (CK) for early breast cancer.MethodsThis pilot study was designed to assess the feasibility of CK-APBI on 20 evaluable patients of 29 eligible, followed for 2 years. The primary endpoint was acute/sub-acute toxicity; secondary endpoints were late toxicity and the cosmetic result.ResultsMean pathological tumor size was 10.5 mm (±4.3, range 3–18), 8 of these patients were classified as LumA-like, 11 as LumB-like, and 1 as LumB-HER2-enriched.Using CK-APBI with Iris, the treatment time was approximately 60 min (range~ 35 to ~ 120). All patients received 30 Gy in five fractions delivered to the PTV. The median number of beams was 180 (IQR 107–213; range:56–325) with a median PTV isodose prescription of 86.0% (IQR 85.0–88.5; range:82–94). The median PTV was 88.1 cm3 (IQR 63.8–108.6; range:32.3–238.8). The median breast V100 and V50 was 0.6 (IQR 0.1–1.5; range:0–13) and 18.6 (IQR 13.1–21.7; range:7.5–37), respectively. The median PTV minimum dose was 26.2 Gy (IQR 24.7–27.6; range 22.3–29.3). Mild side effects were recorded during the period of observation. Cosmetic evaluations were performed by three observers from the start of radiotherapy up to 2 years. Patients’ evaluation progressively increase from 60% to 85% of excellent rating; this trend was similar to that of external observer.ConclusionsThese preliminary results showed the safe feasibility of CK-APBI in early breast cancer, with mild acute and late toxicity and very good cosmetic results.Trial registrationThe present study is registered at Clinicaltrial.gov (NCT02896322). Retrospectively egistered August 4, 2016.
Highlights
Local recurrences after breast conserving treatment are mainly close to the original tumor site, and as such shorter fractionation strategies focused on and nearest mammary gland, i.e. accelerated partial breast irradiation (APBI), have been developed
The large majority of local recurrences after Breast-conserving surgery (BCS) are close to the original tumor site, generally within 2 cm of surgical margins [10, 11], suggesting that it is possible to restrict the radiotherapy target to the surgical cavity in selected patients at low risk of recurrence; in this case, a much smaller volume than the whole breast has to be irradiated, and a more intense course of radiotherapy with fewer and larger dose fractions must be used
A series of 20 evaluable patients is presented to assess the feasibility and safety of CyberKnife radiosurgery system (CK-APBI) in early breast cancer. This pilot phase I prospective study was designed to assess the feasibility of CK-APBI in low risk early breast cancer patients after BCS
Summary
Local recurrences after breast conserving treatment are mainly close to the original tumor site, and as such shorter fractionation strategies focused on and nearest mammary gland, i.e. accelerated partial breast irradiation (APBI), have been developed. Shorter fractionation strategies focusing only on the tumor bed with a small cuff of surrounding subclinical disease, i.e. partial breast irradiation (PBI) or accelerated partial breast irradiation (APBI), have been developed as an alternative to WBRT [12,13,14]. This strategy is further supported by findings from studies using a reduced number of fractions (hypofractionation) [15]
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