Systematic Review of Intensity-Modulated Brachytherapy (IMBT): Static and Dynamic Techniques

Abstract Purpose To systematically review scientific literature on the use of Intensity-Modulated Brachytherapy (IMBT) including static and dynamic shielding approaches to enhance therapeutic ratio. Studies were evaluated in terms of technique, disease site, dosimetry, applicators, dosimetric calculations, and planning algorithms. Comparisons to standard of care brachytherapy (BT) techniques and/or alternate IMBT methods were performed in terms of dose to target volumes, organs at risk (OARs), and treatment planning/delivery times. Methods and Materials Inclusion criteria were any peer-reviewed journal articles on IMBT published from 01/01/80 – 01/01/19 on PubMed, Google Scholar, Cochrane Library, and EBSCO databases. Two independent investigators reviewed each article for inclusion/exclusion criteria and scope. Data collected on each study included technique, source/shield material, disease site, n of study, dose to target/OARs, and planning/delivery times. This review adhered to the Preferred Reporting Items for Systemic reviews and Meta Analyses (PRISMA). Results Database query yielded 1,734 results which were reduced to 436 after exclusion criteria, and 78 peer-reviewed journal articles after evaluation of scope. Studies per disease site were 31, 16, 10, 7, 6, and 8 for cervical, rectal, oculocutaneous, breast, prostate, and other/multiple/no specific disease site respectively. Eighteen studies demonstrated significant decrease in dose to OARs (5.1-68.2%), 11 improved treatment planning/delivery times (7.6-99.7%), and 6 increased target coverage (18.6-71.6%) relative to standard of care or alternate IMBT technique. IMBT consistently decreased dose to OAR compared to standard of care at the cost of increased planning/delivery times. Innovations in dose calculation/planning algorithms and applicators were capable of ameliorating prolonged treatment intervals. Conclusions IMBT techniques improved therapeutic ratio by reducing OAR doses and/or dose escalation. Static shielding techniques are clinically available due to the advent of commercially available heterogeneity-corrected dose calculation algorithms while dynamic shielding techniques are still pre-clinical.