Going to the VMAT-tresses.
Top Line: The more traditional wide tangents and the more sophisticated volumetric modulated arc therapy (VMAT) are common approaches to treating internal mammary nodes (IMN), and they’re ready for a showdown.
The Study: In the modern era, both techniques are usually able to achieve a mean heart dose less than 4 Gy when employing deep inspiratory breath hold. A novel question then becomes: which is less resource intensive? We know, we know, it seems like a forgone conclusion that the winner in that regard is partially wide tangents, and that’s certainly what insurers seem to think. This UK phase 2 trial randomized and analyzed 19 women receiving IMN radiation for left sided breast cancer to wide tangents versus VMAT with a primary endpoint of daily treatment time. We won’t bring up here that the number of treatment days in the UK is only 15, which is pretty resource friendly in itself. The primary outcome of mean total treatment time was more than doubled with wide tangents (28 minutes) than with VMAT (13 minutes), and the beam-on time was 11.2 minutes versus only 2.6 minutes. The mean planning (162 to 188 minutes) and quality assurance (54 to 58 minutes) times were similar. On the other hand, virtually all mean dosimetric parameters to organs at risk were worse with VMAT: mean heart dose 2.6 Gy v 3.4 Gy, respectively, mean volume of ipsilateral lung receiving ≥17 Gy 32.8% v 34.4%, mean humeral head dose 16 Gy v 3 Gy, max esophagus dose 37 Gy v 20 Gy, and mean thyroid dose 22 Gy v 11 Gy.
TBL: In addition to the widely-recognized fact that VMAT-IMN radiation often results in better target coverage at the expense of higher doses to non-target tissues (particularly when not optimized), it also decreases appointment times and the number of breath holds required from patients. | Ranger, Clin Oncol 2022