Purpose. Bilateral postmastectomy irradiation (BPMI) poses a challenge to radiotherapists. The difficulty lies whenever targets are large, irregular and lying at different depths. When breathing movements occur it is very hard to obtain homogenous dosing on such targets and also to not exceed those doses acceptable for at-risk organs, particularly the lungs and heart. The presented study is an example of using a single isocenter Volumetric Modulated Arc Therapy (VMAT) technique for a BPMI case.

Materials and methods. We report the case of a 66-year-old woman with simultaneous malignant sarcoma of the right breast and an invasive ductal carcinoma of the left breast. After modified radical mastectomy of the left breast and simple mastectomy of the right breast, the patient underwent adjuvant irradiation of the bilateral chest wall and left axillary and supraclavicular nodes region. Planning Target Volumes (PTV) and organs at risk (OAR) were deline­ated on CT scans. A single isocenter VMAT plan was created. The radiotherapy consisted of 50 Gy delivered in 2 Gy per fraction to the left side and 56.5 Gy delivered in 2.25 Gy per fraction to the right side in 25 fractions, five times a week over 5 weeks.

Results. The left and right CTV (Clinical Target Volume) received 90% of the prescribed dose in 100% of the CTV volume. The mean heart dose was 14.4 Gy and V25 for the heart was 8.9%. The mean lung dose was 16.6 Gy and the V20 for both lungs was 28.3%. The dose to the anterior wall area of the heart was exceeded according to established constraints, but was accepted. One session of irradiation lasted about four minutes during which the patient received 595 monitor units. The treatment was carried out without interruption and complications. The early and late skin reaction was assessed as being second grade. After one year of follow-up, the patient did not present any serious side effects or recurrence. Conclusions. Synchronous irradiation of both sides of the chest wall after bilateral mastectomy with a single isocenter VMAT technique is possible and well tolerated.