[en] Although 3D-conformal accelerated partial breast irradiation (APBI) is widely used, several questions still remain such as what are the optimal treatment planning modalities. Indeed, some patients may have an unfavorable anatomy and/or inadequate dosimetric constraints could be fulfilled ('complex cases'). In such cases, we wondered which treatment planning modality could be applied to achieve 3D-conformal APBI (2 mini-tangents and an 'en face' electron field or non-coplanar photon multiple fields; or a mixed technique combining non-coplanar photon multiple fields with an 'en face' electron beam). From October 2007 to March 2010, 55 patients with pT1N0 breast cancer were enrolled in a phase II APBI trial. Among them, 7 patients were excluded as they were considered as 'complex cases'. A dosimetric comparison was performed according to the 3 APBI modalities mentioned above and assessed: planning treatment volume (PTV) coverage, PTV/whole breast ratio, lung and heart distance within irradiated field and exposure of organs at risk (OAR). Adequate PTV coverage was obtained with the 3 different treatment planning. Regarding OAR exposure, the 'mixed technique' seemed to reduce the volume of non-target breast tissue in 4 cases compared to the other techniques (in only 1 case), with the mean V_5_0_% at 44.9% (range, 13.4 - 56.9%) for the mixed modality compared to 51.1% (range, 22.4 - 63.4%) and 51.8% (range, 23.1 - 59.5%) for the reference and non-coplanar techniques, respectively. The same trend was observed for heart exposure. The mixed technique showed a promising trend of reducing the volume of non-target breast tissue and heart exposure doses in APBI 'complex cases'

[en] Purpose: Several accelerated partial breast irradiation (APBI) techniques are described in the literature, and apparently, the three-dimensional (3D)-conformal technique is being used increasingly. Nonetheless, the optimal radiation dose is not yet known. Here, we report feasibility and early toxicities of APBI delivering 40 Gy over 5 days, in a phase II trial. Methods and Materials: From October 2007 to September 2008, 25 patients with pT1N0 cancer received 3D-conformal APBI. The prescribed radiation dose was 40 Gy in 4-Gy fractions given twice daily. This technique used two minitangents and an “en face” electron field. Toxicities were systematically assessed at 1, 2, and 6 months and then once every 6 months. Results: The planning tumor volume for evaluation (PTV_EVAL) coverage was adequate: the mean dose to the PTV_EVAL was 41.8 Gy (range, 41–42.4 Gy). Mean doses to the ipsilateral lung and heart were 1.6 Gy (range, 1.0–2.3 Gy) and 1.2 Gy (range, 1.0–1.6 Gy), respectively. One and two months after completion of APBI, most patients had no or mild erythema (n = 16 patients at 1 month; n = 25 patients at 2 months); none of these patients developed moist desquamation. After a median follow-up of 12 months, only 1 patient had a significant moderate field contracture (grade 2). Other reported late toxicities were grade 1. Conclusions: 3D-conformal APBI (with two minitangents and an “en face” electron field) using a total dose of 40 Gy in 10 fractions twice daily over 5 days achieved appropriate PTV_EVAL coverage and offered significant sparing of normal tissue. Early tolerance was excellent.

[en] Recent recommendations regarding indications of accelerated partial breast irradiation (APBI) have been put forward for selected breast cancer (BC) patients. However, some treatment planning parameters, such as total dose, are not yet well defined. The Institut Gustave Roussy has initiated a dose escalation trial at the 40 Gy/10 fractions/5 days and at a further step of total dose (TD) of 42 Gy/10 fractions/ 5 days. Here, we report early results of the latest step compared with the 40 Gy dose level. From October 2007 to March 2010, a total of 48 pT1N0 BC patients were enrolled within this clinical trial: 17 patients at a TD of 42 Gy/10f/5d and 31 at a TD of 40 Gy/10f/5d. Median follow-up was 19 months (min-max, 12–26). All the patients were treated by APBI using a technique with 2 minitangents and an “enface” electrons delivering 20% of the total dose. Toxicities were systematically assessed at 1; 2; 6 months and then every 6 months. Patients’ recruitment of 42 Gy step was ended owing to persistent grade 3 toxicity 6 months after APBI completion (n = 1). Early toxicities were statistically higher after a total dose of 42 Gy regarding grade ≥2 dry (p = 0.01) and moist (p = 0.05) skin desquamation. Breast pain was also statistically higher in the 42 Gy step compared to 40 Gy step (p = 0.02). Other late toxicities (grade ≥2 fibrosis and telangectasia) were not statistically different between 42 Gy and 40 Gy. Early toxicities were more severe and higher rates of late toxicities were observed after 42 Gy/10 fractions/5 days when compared to 40 Gy/10 fractions/5 days. This data suggest that 40 Gy/10 fractions/ 5 days could potentially be the maximum tolerance for PBI although longer follow-up is warranted to better assess late toxicities