Application of 3D printing for personalized boluses in radiotherapy: a systematic review

The goal of this study was to evaluate the current literature covering the topic of 3D-printed radiotherapy boluses in the context of fabrication methods, materials, and clinical outcomes. This systematic review followed the PRISMA 2020 guidelines. Data were extracted for authors, publication details, application type, printing technique and materials, study type, radiation type, reported outcomes and implementation difficulties. The search yielded 161 articles, 52 of which met the inclusion criteria. Publications on 3D printing for customized boluses have increased since 2014, with the most articles from the United States (21%). Most studies (80.8%) focused on manufacturing custom boluses and testing 3D printing materials, whereas 19.2% explored creating molds for boluses. CT scans were the primary method for defining the bolus area (88.6%). The publications included three study types: dosimetric evaluations, evaluations with anthropomorphic phantoms, and clinical case studies. Fused Deposition Modeling (FDM) was the most common printing technique (88.1%), with Polylactic Acid (PLA) being the most frequently used material (57.1%). Challenges included ensuring proper fit, assessing material properties, and managing printing time. The outcomes of this review suggest that 3D printing technology holds significant promise for improving radiotherapy by creating custom-fit boluses. 3D-printed boluses demonstrated notable advantages, such as improved dose distribution, better bolus conformity, and reduced setup times. However, several limitations have been identified, including considerable variability in study designs, making it challenging to draw generalized conclusions. Some studies had small sample sizes or did not clearly report methodological details. Addressing these issues will help to optimize technology's implementation.