Aligning outcomes.

Top Line: We’ve seen big results (10% absolute reductions in grade 3+ mucositis and feeding tube rates) simply by reducing the planning target volume (PTV) margin from 5 mm to 3 mm during head and neck radiation.

The Study: The same Dutch group has now taken it a step further. They compared consecutive patients receiving definitive head and neck radiation before (2013-2015) and after (2017-2019) margins from GTV→CTV→PTV were systematically reduced from a total of 15 mm to 9 mm with daily CBCT. First of all, disease outcomes and survival were similar—in fact numerically better—with tighter margins: local control 76 → 79%, disease-free survival 64 → 71%, and overall survival 68 → 84%. This is despite the median final PTV in the latter cohort being a whopping 28% less than that of the prior cohort. This resulted in significant median reductions of nearly 10 Gy in mean ipsilateral parotid dose and over 6 Gy in mean constrictor muscle dose. More importantly, acute grade 3 toxicity was reduced from 2 in 3 to less than 1 in 2. Specifically, grade 3 mucositis was reduced from 36 → 18% and the rate of feeding tube use at the end of treatment 40 → 25%. Even late toxicity was significantly reduced: grade 2+ xerostomia nearly halved from 59 → 32% and grade 2+ dysphagia from 27 → 15%.

TBL: Better diagnostic and on-board imaging allows for smaller CTV and PTV margins for head and neck cancer radiation, which may significantly reduce acute and late toxicity. | Al-Mamgani, Radiother Oncol 2022