Whole breast radiation therapy in isocentric lateral decubitus position is well tolerated with good cosmesis and low rates of fibrosis, said a group that had previously confirmed the efficacy and safety of the technique. Researchers from the Institut Curie in Paris presented their results during a poster session on Thursday, December 7, at the San Antonio Breast Cancer Symposium.
This study comprised 832 consecutive female patients with early-stage breast cancer who were treated by conservative surgery followed by 3D-conformal whole breast radiation therapy at Institut Curie between 2005 and 2010. Fibrosis and deformation were evaluated at the end of the treatment and subsequently every six months for at least five years, using the National Cancer Institute’s grading scale. Different fractionation schedules were used: 66 Gy in 33 fractions, 50 Gy in 25 fractions, 40 Gy in 15 fractions, 41.6 Gy in 13 fractions, and 30 Gy in 5 fractions.
With a median follow-up of 6.4 years, the majority of women had grade 1 fibrosis (n = 308; 38.9%), with only 36 patients (4.3%) developing grade 2–3 fibrosis. The median time to development of fibrosis was 1.6 years (range: 9 days–8.3 years).
In univariate and multivariate analysis, age, breast size, and chemotherapy administration had no significant influence on development of breast fibrosis. The hypofractionated schedule of 30 Gy in five fractions significantly increased the fibrosis rate (OR = 12.5 [2.7; 57.1], p = 0.001). On the other hand, 40 Gy for 15 fractions and 41.6 Gy for 13 fractions had no significant influence (OR = 2.2 [0.5; 11.1], p = 0.32) as well as the 66 Gy for 33 fractions schedule (OR = 3.6 [0.8; 15.4], p = 0.09) compared to standard scheme of 50 Gy for 25 fractions. The cosmetic result was good or excellent for 84.8% of cases at the first evaluation. Both 30 Gy in five fractions and large breast size influenced the cosmetic result in a multivariate analysis.