ESTRO 2024 - Abstract Book

S4173

Physics - Intra-fraction motion management and real-time adaptive radiotherapy

ESTRO 2024

The observed low toxicity demonstrates that SBRT with plan-library based online adaptation can be safely employed to treat abdominopelvic lymph node oligometastases. This strategy resulted in a one-year local control rate of 96% with minimal toxicity. Currently, this approach has become the standard of care in our department. Regarding the plan selection process, the treatment is carried out without the need for the involvement of a radiation oncologist.

Keywords: Online adaptive, SBRT, oligometastases

References:

1. Papalazarou C, Klop GJ, Milder MTW, Marijnissen JPA, Gupta V, Heijmen BJM, Nuyttens JJME, Hoogeman MS. CyberKnife with integrated CT-on-rails: System description and first clinical application for pancreas SBRT. Med Phys. 2017 Sep;44(9):4816-4827.

634

Digital Poster

Audit of DIBH lung SABR patient positioning accuracy via intra-fractional CBCT imaging

Anna Arns 1,2 , David Little 1,2 , Victoria Beenstock 1,2 , Joanne Maggs 1 , Coutney O'Connor 1 , Julie Groen 1 , Phoebe Chidley 1 , Chris Harrington 1 1 Christchurch Hospital, Te Whatu Ora - Waitaha, Canterbury Regional Cancer and Haematology Service, Christchurch, New Zealand. 2 Christchurch Hospital, Te Whatu Ora - Waitaha, Medical Physics and Bioengineering, Christchurch, New Zealand

Purpose/Objective:

Stereotactic Ablative Radiotherapy (SABR) of lesions in the lung are standardly treated in regular free breathing in our department and is generally well tolerated by patients. In early 2023 however, two complex lung SABR patients were not suitable for free-breathing technique and were treated in deep-inspiration breath-hold (DIBH) instead. After successful treatment of these two patients, we initiated a pilot study on lung SABR in DIBH. Our aim was to establish an alternative treatment technique for patients with potential clinical benefit of treatment in DIBH: lesions in lower lobe lung and/ or central lung lesions close to critical organs. A retrospective patient set-up audit on intra-fractional imaging (IFI) during treatment beam delivery was performed to evaluate successful treatment delivery to the target, and to assess potential for future planning target volume (PTV) reduction to further spare critical organs.

Material/Methods:

To date, 8 patients were treated with lung SABR in DIBH, including the 2 initial exception cases. Adapted from our standard free-breathing technique, all patients were treated with Monte-Carlo based inverse-planned partial arc DCAT (dynamic conformal arc therapy), a “VMAT-lite” approach with only minimal MLC modulation (Monaco, Elekta,