Outcomes of and treatment planning considerations for a hybrid technique delivering proton pencil-beam scanning radiation to women with metal-containing tissue expanders undergoing post-mastectomy radiation. (November 2021)

• Record Type: Journal Article
• Authors: DeCesaris, Cristina M.; Mossahebi, Sina; Jatczak, Jenna; Rao, Avani D.; Zhu, Mingyao; Mishra, Mark V.; Nichols, Elizabeth
• Is Part Of: Radiotherapy and oncology. Volume 164(2021)
• Page Start: 289
• Page End: 298
• Publication Date: 2021-11
• Subjects: Protons -- breast neoplasms -- mastectomy; Oncology -- Periodicals; Radiotherapy -- Periodicals; Tumors -- Periodicals; Medical Oncology -- Periodicals; Neoplasms -- radiotherapy -- Periodicals; Radiotherapy -- Periodicals; Radiothérapie -- Périodiques; Cancérologie -- Périodiques; Tumeurs -- Périodiques; Electronic journals; 616.9940642
• DOI: 10.1016/j.radonc.2021.07.012
• Languages: English
• ISSNs: 0167-8140

Abstract

Highlights: Details of technique, including beam angles, anatomic criteria, and image guidance. Descriptions of target coverage and doses to OARs, and acute toxicity profiles. Figures/images as visual guides for beam arrangements and expected dose distributions. Abstract: Background: Following mastectomy, immediate breast reconstruction often involves the use of temporary tissue expanders (TEs). TEs contain metallic ports (MPs), which complicate proton pencil-beam scanning (PBS) planning. A technique was implemented for delivering PBS post-mastectomy radiation (PMRT) to patients with TEs and MPs. Methods: A protocol utilizing a hybrid single- and multi-field optimization (SFO, MFO) technique was developed. Plans were robustly optimized using a Monte Carlo algorithm. A CTV_eval structure including chest wall (CW) and regional nodal (RNI) targets and excluding the TE was evaluated. Organ at risk (OAR) dosimetry and acute toxicities were analyzed. Results: Twenty-nine women were treated with this technique. A 2-field SFO technique was used superior and inferior to the MP, with a 3 or 4-field MFO technique used at the level of the MP. Virtual blocks were utilized so that beams did not travel through the MP. A port-to-CW distance of 1 cm was required. Patients underwent daily image-guidance to ensure the port remained within a 0.5 cm internal planning volume (ITV). Median RT dose to CTV_eval was 50.4 Gy (45.0–50.4). Median 95% CTV_eval coverage was 99.5% (95–100). Optically stimulated luminescent dosimeter (OSLD) readings were available for 8 patients and correlated to the dose measurements in the treatment planning system (TPS); median OSLD ratio was 0.99 (range, 0.93–1.02). Conclusions: Delivering PMRT with PBS for women with metal-containing TEs using a hybrid SFO/MFO technique is feasible, reproducible, and achieves excellent dose distributions. Specialized planning and image-guidance techniques are required to safely utilize this treatment in the clinic.