A thought-provoking dosimetric analysis of 50 lung SBRT plans indicates optimizing median dose to the 4D-tumor (ITV) best translates to realized delivered dose to tumor during a free-breathing treatment. This is opposed to the more commonly used objective of minimum coverage to 95-100% of the planning target volume (PTV) that often results in a dosimetric translation error between the prescribed PTV coverage and the true ITV dose. That’s because, with modern heterogeneity-corrected algorithms, the PTV contains a lot of lung, so its D95/D98 can be strongly affected by the amount of low-density lung surrounding the tumor. Two patients can both have a PTV D95% of 100% while received tumor doses are meaningfully different. By contrast, in this study, GTV D50% (i.e. median dose) tracked the true dose delivered over the breathing cycle much more consistently. The authors argue for calculating the ITV median dose on the CT-average as the prescription anchor, while PTV D95-100 should be viewed more as a coverage/safety check rather than the best representation of the delivered tumor dose. | Cirop, Pract Radiat Oncol 2026
