Treatment planning evolution: Comparing approaches in photodynamic and radiation therapies

The setups of previous and ongoing clinical trials are based on prescribed PDT doses, PS concentration, and light intensity derived from averages of previous clinical or study populations. It is understood that monitoring of personalized PS and light dose is needed to improve PDT outcomes. Monitoring of photophysical, photochemical, or cytotoxic moieties is common, representing concepts of delivered, absorbed, or equivalent doses similar to those used in radiation therapy (RT). Unlike RT, these dose concepts are not equally well developed and standardized across the PDT clinical indications; however, there is potential to improve PDT treatment setup, planning, and delivery by leveraging methodologies from RT. This review summarizes dose definitions and advancements in RT treatment planning and presents the equivalent dose concepts for PDT, particularly how these concepts can expand on the existing methods for PDT treatment planning. By identifying the major limitations and areas for improvement in PDT planning, the hope is to stimulate preclinical and clinical research studies that can enhance the efficacy of PDT, improving patient outcomes.