Partial breast irradiation with CyberKnife after breast conserving surgery: a pilot study in early breast cancer

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.

First Experience in Korea of Stereotactic Partial Breast Irradiation for Low-Risk Early-Stage Breast Cancer

“…This could be explained by the substantial PTV margin expansion mandated by respiratory and setup uncertainties in 3D-CRT. Likewise, our delicate S-PBI planning achieved consistent dosimetric profiles compared to those observed in Western S-PBI studies in other organs-atrisk, without compromising PTV coverage or creating PTV hot spots (9,21,22). These results demonstrated that S-PBI could overcome the disadvantage of relatively small breast volumes in Korean women.…”

“…As a result, not only were the ipsilateral breast dosimetric goals successfully satisfied in all breasts in our study, but the median ipsilateral breast V 50% in our study was 35.8%, much lower than that of the KROG study (20). Compared to the Western A-PBI reports (Table S2), the ipsilateral breast V 50% in our patients was as low as those in Western S-PBI studies (9,21,22), and dramatically lower than in A-PBI studies using three-dimensional conformal radiation therapy (3D-CRT), ranging from 42 to 49% (23)(24)(25)(26). This could be explained by the substantial PTV margin expansion mandated by respiratory and setup uncertainties in 3D-CRT.…”

Implementation of Stereotactic Accelerated Partial Breast Irradiation Using Cyber-Knife – Technical Considerations and Early Experiences of a Phase II Clinical Study

“…Very mild toxicities occurred, 100% of the patients had good-excellent cosmesis. Lozza et al published a pilot study in 2018, they treated 20 patients with CK-SAPBI using the Iris collimator [ 32 ]. The total dose was 30 Gy in 5 consecutive fractions and were prescribed to the isodose line include 95% of the PTV.…”

Intrafraction motion during partial breast irradiation depends on treatment time

“…Due to the reduced number of fractions, there is a possibly larger impact of a geographical miss of the target, with hence a potential increase in the risk of local recurrence. Most current hypofractionated external beam APBI (EB-APBI) protocols use daily online positioning verification and correction based on cone beam CT or kV imaging, or more recently MR imaging [13,[15][16][17]. The motion that occurs after this setup and during the treatment delivery, is often not considered.…”