Whole breast radiotherapy in the isocentric lateral decubitus position: Role of the immobilization device and table on clinical results

Abstract Purpose To evaluate clinical results and the “effect bolus” based on the table design of different linear accelerators in patients with breast cancer treated by previously published whole breast irradiation in the isocentric lateral decubitus position. Material and methods We studied 248 consecutive female patients with early stage breast cancer treated by conservative surgery followed by three-dimensional conformal whole breast irradiation in the isocentric lateral decubitus position between January 2013 and February 2014. Radiotherapy was performed on linear accelerators using a Varian. The energy used was 4 and 10 MV photons or 6 MV photons. All patients were evaluated weekly by the radiation oncologist, acute toxicity was assessed using the NCICTC v 3.0 scale. Late toxicity and cosmetic results were evaluated 18 months after the radiotherapy. Cosmetic results were defined as excellent, good, middle or bad. Results Among the 248 women included, the median age was 67 years (range: 35–91 years). All received whole breast radiotherapy with boost in 144 patients (58%). One-hundred-twenty patients received normofractionated and 124 patients hypofractionated whole breast radiotherapy. Median follow-up was 18 months. Acute skin toxicity in the whole breast radiotherapy in the isocentric lateral decubitus position was acceptable: there was 47% of grade 1 radiodermatitis, 50% of grade 2 and 3% grade 3 and no grade 4 for normofractionated radiotherapy; 89% of grade 1 dermatitis and 11% of grade 2 for hypofractionated radiotherapy; 89.7% of grade 0–1 dermatitis and 10.3% of grade 2 for the “flash” scheme and did not differ between the three linear accelerators ( P  = 0.2, P  = 0.9 and P  = 0.2 respectively for the normofractionated radiotherapy, hypofractionated radiotherapy and the “flash”scheme). Late toxicity was acceptable with 84% of grade 0–1 fibrosis for normofractionated radiotherapy, 94% of patients for hypofractionated radiotherapy and 77% for “flash” scheme and did not differ between the three linear accelerators ( P  = 0.44, P  = 1 and P  = 0.22 resp.). Most of patients (81%) had an excellent or a good cosmetic outcome. Conclusions Whole breast radiotherapy in the isocentric lateral decubitus position is well tolerated. Clinical results are comparable based on different immobilization device allowed by linear accelerators. Particularly, there was no influence of the couch on skin tolerance and cosmetic results.