S235
Clinical - Breast
ESTRO 2026
Marsden NHS Foundation Trust, London, United Kingdom
Purpose/Objective: Breast cancer is the most common malignancy in the UK, with 57,000 women diagnosed annually (1). Radiotherapy is a key adjuvant treatment (2) and advances such as hypofractionation (26 Gy in 5 fractions) and widespread adoption of deep inspiration breath hold (DIBH) have reduced treatment burden and cardiac exposure (3, 4). However, real- world data on contemporary heart and lung doses remain limited. Material/Methods: Following the national implementation of a cloud- based dosimetry repository (ProKnow) in 2022, NHS England initiated a national breast radiotherapy audit to evaluate data quality and dosimetric outcomes. All 49 radiotherapy centres in England were invited to upload treatment plans to national breast collections, stratified by location (left/right) breast only (26Gy/5#), breast & axilla (40Gy/15#), breast & Internal mammary chain (40Gy/15#). Data was cleaned to exclude erroneous or incomplete plans. Dose–volume metrics and treatment technique were analysed for the heart and ipsilateral lung according to national “scorecard” constraints. Results: 48 of 49 centres participated, contributing nearly 30,000 plans (90.6% analysable). Data quality was high, with only 4.1% upload errors and 5.3% excluded due to missing contours. For breast/chest wall-only treatments, 98% of left-sided and 99.9% of right-sided cases achieved mean heart doses (MHD) below 2 Gy, with a median of 0.57 Gy (left) and 0.25 Gy (right). For nodal plans including internal mammary chain (IMC), median MHDs were 3.4 Gy (left) and 2.3 Gy (right), with 98% of all plans meeting the 6 Gy suggested constraint.Mean ipsilateral lung doses were generally within recommended limits; 93% of breast-only and 96% of nodal-IMC plans met optimal V7.8–V17 Gy suggested criteria. VMAT was used in 0.4% of breast- only, 10% of nodal-non-IMC, and 65–80% of IMC plans. VMAT provided superior PTV coverage but higher MHDs compared to IMRT/static techniques. Conclusion: This first national radiotherapy audit using ProKnow demonstrates the feasibility of large-scale, real-world dosimetric evaluation across England. Cardiac doses are reassuringly low and comparable to international benchmarks, though variation exists between centres, particularly in VMAT planning. The audit identifies opportunities for quality improvement, including refinement of suggested national dose constraints, enhanced data completeness, and future inclusion of boost plansThe NHS Breast Radiotherapy Audit provides the most comprehensive national overview
Conclusion: The risk of telangiectasia was significantly increased with bolus application. Local recurrence after PMRT was rare and not high for patients with T1-2 cancer treated without bolus, indicating that omitting bolus for T1–T2 breast cancer appears safe. These data, derived from the largest contemporary cohort examining bolus use, local recurrence, and late effects after PMRT, suggest that limiting bolus application may be appropriate and highlight the importance of individualized patient selection to balance disease control against the risk of telangiectasia. Keywords: Bolus, Late effects, Radiotherapy
Proffered Paper 1242
UK National Breast Radiotherapy Audit: Real- World Heart and Lung Doses from 30,000 NHS Treatment Plans Nathaniel Luke Hatton 1,2 , Vibeke Hansen 3 , Ryan Fullarton 3 , Imogen Locke 3 , Michael Thomas 3 1 Oncology, Leeds Teaching Hospital Trust, Leeds, United Kingdom. 2 Radiotherapy, NHS England, London, United Kingdom. 3 Radiotherapy, Royal
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