Exposure of the lungs in breast cancer radiotherapy: A systematic review of lung doses published 2010-2015

Background and purpose: We report a systematic review of lung radiation doses from breast cancer radiotherapy.

Methods and materials: Studies describing breast cancer radiotherapy regimens published during 2010-2015 and reporting lung dose were included. Doses were compared between different countries, anatomical regions irradiated, techniques and use of breathing adaptation.

Results: 471 regimens from 32 countries were identified. The average mean ipsilateral lung dose (MLD_ipsi) was 9.0 Gy. MLD_ipsi for supine radiotherapy with no breathing adaption was 8.4 Gy for whole breast/chest wall (WB/CW) radiotherapy, 11.2 Gy when the axilla/supraclavicular fossa was irradiated, and 14.0 Gy with the addition of internal mammary chain irradiation; breathing adaptation reduced MLD_ipsi by 1 Gy, 2 Gy and 3 Gy respectively (p < 0.005). For WB/CW radiotherapy, MLD_ipsi was lowest for tangents in prone (1.2 Gy) or lateral decubitus (0.8 Gy) positions. The highest MLD_ipsi was for IMRT in supine position (9.4 Gy). The average mean contralateral lung dose (MLD_cont) for WB/CW radiotherapy was higher for IMRT (3.0 Gy) than for tangents (0.8 Gy).

Conclusions: Lung doses from breast cancer radiotherapy varied substantially worldwide, even between studies describing similar regimens. Lymph node inclusion and IMRT use increased exposure, while breathing adaptation and prone/lateral decubitus positioning reduced it.