Top Line: There are many trade-offs when optimizing a head and neck treatment plan, so how do you know when a plan is the best it can be?
The Study: We typically use standard, population-based dose constraints to judge plan quality. Depending on tumor and patient anatomy, though, some plans could do much better while others may never achieve desired organ-at-risk (OAR) objectives. This study sought to determine if knowledge of the best feasible dose to OARs prior to treatment planning could improve dosimetry in head and neck treatment plans. Software, called PlanIQ, was used to generate a patient-specific “idealized” DVH for different OARs prior to treatment planning. This feasibility DVH (FDVH) is not an actual treatment plan. It’s an estimate of the best possible DVH given coverage of the target volume and dose falloff within the patient. In other words, it can provide patient-specific planning goals, such as the best achievable OAR mean dose and max dose, prior to IMRT optimization. The authors found that, compared to pre-implementation, FDVH-based knowledge of feasible OAR dosimetry resulted in significant improvements in dose to multiple OARs. The excess mean dose (i.e. the difference between the mean feasible dose and the actual mean dose) was significantly reduced with knowledge of the FDVH for the oral cavity, bilateral parotids, and larynx. There was a 60% relative reduction in excess ipsilateral parotid dose, a 43% reduction in excess contralateral parotid dose, and a 34% reduction in excess larynx dose. In addition, FDVH knowledge led to considerably less variation in excess mean OAR dose. Finally, improvements in OAR dosimetry resulted in improved patient-reported outcomes related to salivary and swallowing function.
TBL: Having knowledge of the best feasible dose to OARs during head and neck treatment planning significantly improves plan quality, which translates to improved patient-reported outcomes. | Fried, Pract Radiat Oncol 2021