Physician/patient-driven risk assignment in radiation oncology: reality or fancy?

Treatment plan optimization in radiation oncology entails designing multiple x-ray beams to irradiate a tumor to a dose that will achieve locoregional control while minimizing normal tissue complications. For some anatomical sites, it is possible to estimate tumor control probabilities (TCP) and normal tissue complication probabilities (NTCP) as a function of radiation dose. Thus, treatment plan optimization can be based on biologic end points rather than on dose calculations alone. Given multiple plans with different NTCPs and TCPs, a tradeoff must be made between maximizing TCP and maintaining an acceptable NTCP. How do physicians reach these decisions? Can the process be quantified? Should patients participate in the process?

Physicians and patients were asked to rank a series of treatment plans having different combinations of TCP and NTCP. Responses were parametrized into a figure of merit (FM) equation which quantifies predilections of TCP and NTCP.

Physician-based FM equations are site- and patient-specific. Variations exist among physicians, but treatment plan selection is often conservative in accordance with the primum non nocere dictum. FM equations generated from the responses of patients suggest that some patients may be willing to accept higher treatment toxicity in exchange for increased TCP.

The term "optimized treatment plan" contains inherently subjective criteria which reflect one's willingness to accept treatment morbidity in exchange for probability of cure. These criteria may differ among patients and/or physicians. A quantifiable FM may permit the design of custom-made treatment plans that include physician and patient input.