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Radiotherapy treatment of breast and regional nodes increasingly include internal mammary chain (IMC) as evidence has emerged showing survival benefits in patients with high risk of locoregional recurrence [1]. This study aimed to examine the variations of breast IMC radiotherapy practice in the United Kingdom (UK).

Axillary Management in Breast Cancer Patients With Needle Biopsy Proven Nodal Metastases After Neoadjuvant Chemotherapy (ATNEC), ClinicalTrials.gov: NCT04109079, is a randomised phase III trial investigating whether axillary treatment can be avoided in patients with no residual cancer in the lymph glands after chemotherapy.

As part of the ATNEC Quality Assurance (QA) programme a pre-trial questionnaire was circulated to centres that expressed an interest in participating in the trial. The questionnaire was designed to capture participating centres’ breast IMC radiotherapy practice in terms of target volume delineation, radiotherapy planning techniques, motion management and treatment verification approaches. 

Between September 2019 to August 2021, 27 UK centres completed the questionnaires and the results were summarised in figure 1.

ATNEC mandates target volume delineation for radiotherapy planning and 16/27 centres (59%) did not routinely delineate regional nodes. For treatment planning techniques, 17/27 centres were using volumetric modulated arc therapy (VMAT) and 20/27 centres used wide tangential techniques. All participating centres used deep inspiration breath hold (DIBH) as the motion management approach for delivery breast IMC radiotherapy.

In terms of treatment verification, the practice varied from centre to centre and were mostly dependent on the use of planning technique and fractionation regime. 2D MV/KV imaging (21/27 centres) were most commonly used; Cone-beam computed tomography (CBCT) was used by some centres when VMAT technique was employed.  It is noted all Elekta centres used CBCT for treatment verification. There were some variations in the frequency of imaging; 4 centres used daily CBCT for image verification, whereas the majority of the centres imaged using kV imaging on the first three fractions followed by weekly imaging. 

This study indicated differences in breast IMC radiotherapy practice among ATNEC participating centres in the UK.  Although some centres routinely used field-based techniques, they implemented volume-based breast IMC radiotherapy through the trial QA programme. Findings from this pre-trial QA questionnaire provided reassurance that all ATNEC participating centres could comply the standards as required in the trial protocol.