The Study: Why? Because treatment planning can often involve huge tradeoffs between tumor coverage and significant toxicity from a who’s who list of human organs. So what comes at the heels of practical data? Yup, international expert consensus guidelines. For starters, they recommend planning reference volumes (PRVs) of at least 2 mm around organs-at-risk (OAR) to account for setup variation. All planning structures (targets and OARs) are then divided into 1 of 4 categories. Priority 1 OARs (optic nerves/chiasm, brainstem, and spinal cord) are respected at all costs. If PTV coverage must be sacrificed for these OARs, they recommended either adaptive replanning or induction chemo. Priority 2 structures include target volumes and the temporal lobes, followed by the lesser priority 3 and 4 OARs. Table 2 is a tape-to-the-wall-in-dosimetry kind of table, actually providing a spectrum of ideal to acceptable doses to targets and OARs and when to prioritize what.
TBL: Fear NPC treatment planning no more. | Lee, Int J Radiat Oncol Biol Phys 2019