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

Abstract

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.

Keywords: Breast cancer; Breathing adaptation; Imrt; Lung dose.

Fig. 1

The process of study identification for the review.

Fig. 2

Mean ipsilateral lung dose (MLD_ipsi) from left or right tangential breast cancer radiotherapy according to country, gross national income per person in the country concerned, calendar year, and whether the radiotherapy plans were actually delivered or just planned. Regimens that irradiated the internal mammary chain, partial breast, axilla, or supraclavicular fossa were excluded, as were regimens with breathing adaptation, prone or lateral decubitus positioning and studies of women with unfavourable anatomy. *Average of mean ipsilateral lung doses for reported regimens. †Range of mean ipsilateral lung doses for reported regimens. χ² and p values are for: heterogeneity (a), difference (b, d) or trend (c). For (d), the category “Not specified” was omitted from the χ². Abbreviations: SE: standard error; CI: confidence interval.

Fig. 3

Mean ipsilateral lung dose (MLD_ipsi) from left or right breast cancer radiotherapy according to regions irradiated. Studies of women with unfavourable anatomy were excluded as were regimens using prone or lateral decubitus positioning, and regimens irradiating the internal mammary chain (IMC) but not the axilla or the supraclavicular fossa (SCF). *Average of mean ipsilateral lung doses for reported regimens. †Range of mean ipsilateral lung doses for reported regimens. χ² and p values are for heterogeneity. Abbreviations: SE: standard error; CI: confidence interval.

Fig. 4

Mean ipsilateral lung dose (MLD_ipsi) from left or right breast cancer radiotherapy according to regions irradiated and technique used. Regimens using breathing adaptation (e.g. deep inspiration breath hold) were excluded, as were studies of women with unfavourable anatomy and regimens irradiating the internal mammary chain (IMC) but not the axilla or the supraclavicular fossa (SCF). *Average of mean ipsilateral lung doses for reported regimens. †Range of mean ipsilateral lung doses for reported regimens. ‡Static field IMRT and rotational IMRT are included jointly as “IMRT”. § “Other” techniques included two dynamic conformal arc therapy regimens and one unspecified 3D conformal regimen. χ² and p values are for heterogeneity. Abbreviations: SE: standard error; CI: confidence interval; IMRT: intensity modulated radiotherapy. IMC: internal mammary chain. SCF: supraclavicular fossa.

Fig. 5

Mean ipsilateral lung doses (MLD_ipsi) from left or right breast cancer radiotherapy with or without breathing adaptation according to regions irradiated and regimens used. Only studies providing doses with and without breathing adaptation in the same woman were included. Studies of women with unfavourable anatomy were excluded. *Average of mean ipsilateral lung doses for reported regimens. †Range of mean ipsilateral lung doses for reported regimens. ‡Static field IMRT and rotational IMRT are included jointly as “IMRT”. § “Other” includes one unspecified 3D conformal regimen. p values are calculated using a paired t-test. Abbreviations: CI: confidence interval; IMRT: intensity modulated radiotherapy; IMC: internal mammary chain; SCF: supraclavicular fossa.