National audit assesses normal tissue doses in breast cancer radiotherapy across England

Evidence before this study

We searched PubMed from database inception to Feb 27, 2026, with no language restrictions, using the search string “(“Breast Neoplasms” OR “breast cancer”) AND (“radiotherapy” OR “radiotherapy” OR “radiation therapy”) AND (“radiotherapy dosage” OR dosimetry OR “treatment planning” OR “radiotherapy planning”) AND (“population-based Studies” OR “population” OR “population-based” OR “real world” OR “real-world” OR “audit” OR “registry” OR “registries” OR “national” OR “database”)”. We identified three previous population-based dosimetry audits, the largest of which was a Danish Breast Cancer Group (DBCG) population-based retrospective audit of heart doses in 6925 patients treated for breast cancer with locoregional radiotherapy between 2008 and 2016. This audit, which applied auto-segmentation tools retrospectively to radiotherapy planning CT scans acquired via the DBCG RT Nation Study, showed that the median mean heart dose (MHD) across the whole cohort (left-sided and right-sided cases) was less than 2 Gy. In the UK, hypofractionation trials and studies of deep inspiration breath-hold have informed radiotherapy planning priorities for adjuvant breast cancer radiotherapy, but large-scale, real-world dosimetric data remain sparse, precluding national benchmarking and systematic assessment of inter-centre variation.

Added value of this study

This study reports the first comprehensive national audit of normal tissue doses in breast cancer radiotherapy based on a cloud-based repository of radiotherapy treatment plans in the UK National Health Service. 30 582 individual treatment plans were uploaded from 48 of 49 radiotherapy centres in England in 2025, relating predominantly to patients treated in 2023–24. The study shows the feasibility of routine, near-real-time collection and evaluation of radiotherapy dosimetry at scale with high data completeness and participation. Heart and lung doses achieved in routine practice were consistently within constraints, with more than 99% of breast, chest wall, or partial-breast radiotherapy plans being within the nationally agreed suggested MHD constraint of 2 Gy. MHD findings in other clinical settings were consistent with contemporary research studies. However, the analysis identified clinically relevant inter-centre variation and technique-specific trade-offs providing a pragmatic evidence base for quality improvement.

Implications of all the available evidence

Building on evidence from practice-changing UK trials of breast cancer radiotherapy, these findings show that contemporary real-world practice consistently achieves MHDs of less than 2 Gy for breast or chest wall-only radiotherapy. Further reductions in heart and lung doses are most likely to come from improved standardisation and optimisation of regional nodal irradiation, particularly when using more advanced arc therapy techniques. National radiotherapy data repositories can benchmark practice, provide reassurance that suggested dose constraints are being met, reduce unwarranted variations in practice, and ultimately support more personalised benefit–risk decision making through linkage with clinical and patient-reported outcomes.

Source: The Lancet Oncology