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Active Breathing Control (ABC) is a motion management strategy that facilitates reproducible inspiratory breath-hold for thoracic radiotherapy (RT) to reduce intra-fraction respiratory-related target and organ displacement. This has been shown to reduce radiation dose to organs at risk (OARs). Reduction of treatment-induced late toxicity is of especially high importance in children. However, there is little published literature on the feasibility of using ABC in younger patients. The purpose of this study was therefore to report our institutional experience of using ABC for paediatric and teenage patients.

Following institutional review board approval, all patients aged ≤ 18 years referred for thoracic RT using ABC at our centre from 2013 to 2021 were identified. Electronic patient and RT records were retrospectively reviewed to obtain information on diagnosis, RT dose and technique, OAR dosimetry, tolerability of ABC, post-treatment imaging and early toxicity rates. Descriptive statistics were used and patients grouped into those receiving mediastinal RT (e.g. lymphoma) and ipsilateral thoracic tumours, including hemithorax RT (e.g. sarcoma), for the reporting of OAR dosimetry.

In total, 12 patients had thoracic RT with ABC; median age 15.5 yrs (range, 10-18 yrs). The diagnoses were as follows: 5 Hodgkin lymphoma, 1 mediastinal B cell lymphoma, 5 Ewing sarcoma and 1 rhabdomyosarcoma. All patients have managed to comply with ABC during planning and for the duration of RT: 11 patients have completed RT, and 1 patient is still undergoing RT. The most common RT technique used was VMAT (n=9) with the remainder treated using IMRT (n=1) or conformal RT (n=2).

For mediastinal RT cases (n=6), median dose prescribed was 30.6Gy (range, 19.8-40Gy), median mean heart dose was 11.4Gy (range, 4.8-19.4Gy), median mean lung dose was 9.9Gy (range, 5.7-14.5Gy) and mean lung V20 was 8.3%.

For ipsilateral RT cases, (n=6), median hemithorax and total doses to primary tumour were 18Gy (range, 15-20Gy) and 52.2Gy (range, 36-60Gy) respectively. Median mean heart dose was 19.5Gy (range, 10.6-33.2Gy) and median mean lung dose was 17.7Gy (range, 16.3-30.5Gy). Mean bilateral lung V20 was 39.6%. Median mean contralateral lung dose was 5.2Gy (range, 3.5-11.6Gy) and mean contralateral lung V20 was 5.7%.

At 3 months, 4/11 patients had radiological changes consistent with radiation pneumonitis, but only 1 was symptomatic (CTCAE v4.0 grade 2). At a median follow up of 36 months, only 1 patient had symptomatic radiation pneumonitis having received further thoracic RT for relapse. 

ABC is a feasible and well tolerated motion management technique for younger patients receiving thoracic RT, with children as young as 10 yrs able to comply. The use of ABC results in heart and lung doses which are comparable to similar data in adults and can facilitate RT for extensive thoracic sarcoma.