- Radiotherapy Physics
- Sarah De Vos
- Training location
- Royal Liverpool and Broadgreen University Hospitals NHS Trust; and the Clatterbridge Cancer Centre NHS Foundation Trust
Introduction Lung cancer is the deadliest type of cancer, and eight in 10 lung cancers are NSCLC. There is evidence that cardiac dose contributes to reduced overall survival in NSCLC patients. If cardiac dose can be minimized in the treatment of these patients, without impacting on PTV dose, or other OARs, this may improve their prognosis. This study will aim to develop cardiac avoidance treatment planning techniques for NSCLC patients. Methodology Twenty-three patients were included in the study. Three new plans were created retrospectively: a second plan (B) was morphed from the original delivered plan (A), where the cardiac dose objectives (mean heart dose (MHD), V5Gy and V30Gy) were pushed harder in the optimiser. For the third plan (C), the full or half arcs were replaced by partial arcs, with cardiac avoidance sectors, in a coplanar orientation. The fourth plan has the same partial arcs as the third plan, but in a noncoplanar orientation, to further drive heart dose down. For a small subset of patients, a more extreme noncoplanar arc configuration (seven partial arcs) was created. Plans were compared and evaluated with statistical analysis, using a range of PTV and OAR dosimetric parameters. Results MHD, V5Gy and V30Gy were improved for all three new plans, compared with the clinical plan (A). The largest improvements in heart dose were observed for the noncoplanar partial arc geometry (D), followed by the coplanar full/half arc geometry with tighter planning objectives (B). MHD reduced by 32.4% for Plan D, compared with Plan A (P < 0.001), whereas heart V5Gy and V30Gy saw a reduction of 26.1% (P < 0.001) and 38.8% (P < 0.001) respectively. For Plan B, compared to A, the mean reduction in MHD, heart V5Gy and V30Gy was 25.7% (P = 0.001), 17.6% (P = 0.002) and 35.7% (P < 0.001) respectively. Oesophagus dose increased significantly for Plan B (2.2%, P = 0.009), and Paddick CI decreased significantly for Plan D (3.3%, P = 0.0200) but on the whole OAR doses and PTV coverage either improved or remained similar between plans. Conclusions It is possible to develop cardiac avoidance treatment planning for NSCLC patients undergoing VMAT treatment (55Gy in 20#) without significantly compromising other OARs or PTV coverage.