Feasibility of modified target volumes to meet potential therapeutic needs for nasopharyngeal carcinoma

Precision radiotherapy for nasopharyngeal carcinoma (NPC) typically involves multiple target volumes and dose gradients. However, there is no consensus on the optimal number of targets or gradients. This study investigates whether simplifying target settings and optimizing dose distribution could maintain efficacy while reducing toxicity.

100 newly diagnosed NPC patients treated with volumetric modulated arc therapy (VMAT) were randomly selected. Two radiotherapy planning models were compared: Model A included two target volumes (GTV and CTV2) with corresponding dose gradients; Model B included three target volumes (GTV, CTV1, CTV2) and three gradients. Dosimetric parameters were analyzed under RTOG criteria. Long-term follow-up was conducted to assess survival outcomes and treatment-related toxicities, including normal tissue complication probability (NTCP).

Model A demonstrated a natural dose fall-off where 95 % of PCTV1 was covered by PGTV1, with an average dose of 6456.32 ± 156.74 cGy. In Model B, 95 % of PCTV1 received 6119.20 ± 222.03 cGy, showing no significant dosimetric difference. One-year follow-up indicated no compromise in disease control or survival in Model A. Notably, Model A showed reduced adverse effects; the NTCP of the parotid gland was lower (0.11 ± 0.08) compared to Model B (0.12 ± 0.06).

Omitting CTV1 and its dose gradient while fine-tuning remaining targets achieves comparable dosimetry and clinical outcomes, with reduced toxicity.

This simplified target setting strategy offers a viable alternative to traditional NPC radiotherapy planning, potentially streamlining clinical workflow and improving patient comfort without compromising therapeutic efficacy.