Role of primary tumor volume and metastatic lymph node volume in response to curative effect of definitive radiotherapy for locally advanced head and neck cancer
Authors: Mao Weiling , Zhang Tao , Li Longhao , Peng Siyun , Gong Huiying , Li Minmin 
Published: February 2024

Abstract
Background
Studies have shown mixed results concerning the role of primary tumor volume (TV) and metastatic lymph node (NV) volume in response to the curative effect of definitive radiotherapy for locally advanced head and neck squamous cell carcinoma (LAHNSCC).

Objective
We aimed to evaluate the impact of TV and NV on the efficacy of radical radiotherapy in LAHNSCC patients, with the goal of guiding individualized therapy.

Patients and methods
Patients with LAHNSCC who received radical radiation therapy and were reexamined within 6 months post-therapy from January 2012 to December 2021 were selected. The volumes of the primary tumors and metastatic lymph nodes were calculated by software and then were divided into a large TV group vs small TV group and a large NV group vs small NV group according to the relationship with the median. Additionally, patients who received concurrent chemoradiotherapy (CCRT) or not were divided into the CCRT group and the radiotherapy (RT) group. Patients with lymph node metastasis were divided into node concurrent chemotherapy (N-CCRT) group and a node metastatic chemotherapy (N-RT) group according to whether they received concurrent chemotherapy or not. The volume shrinkage rate (VSR), objective response rate (ORR), local control rate (LCR) and overall survival (OS) were recorded and analyzed.

Results
96 patients were included in the primary tumor volume group, and 73 patients were included in the metastatic lymph node group. Receiver operating characteristic (ROC) curves were constructed for objective remission (OR) endpoints, and a volume threshold was defined for TV and NV patients. The threshold primary tumor volume was 32.45 cm3, and the threshold metastatic lymph node volume was 6.05 cm3.The primary TV shrinkage rates of the small TV and the large TV groups were basically the same, P = 0.801. Similarly, the ORR and LCR were not significantly different between the small TV group and the large TV group (PORR = 0.118, PLCR = 0.315). Additionally, the TV shrinkage rate did not significantly differ between the CCRT group and the RT group, P = 0.133. Additionally, there was no significant difference in ORR or LCR in CCRT group (PORR = 0.057, PLCR = 0.088). However, the metastatic lymph node volume shrinkage rate in the small NV group was significantly greater than that in the large NV group (P = 0.001). The ORR and LCR of the small NV subgroup were significantly greater than those of the large NV subgroup (PORR = 0.002, PLCR = 0.037). Moreover, compared with that of the N-RT group, the NV shrinkage rate of the N-CCRT group was 84.10 ± s3.11%, and the shrinkage rate was 70.76 ± s5.77% (P = 0.047). For the ORR and LCR, the N-CCRT group and N-RT group were significantly different (PORR = 0.030, PLCR = 0.037). The median OS of the whole group was 26 months. However, neither TV/NV nor concurrent chemotherapy seemed to influence OS.

Conclusion
Primary tumor volume is not a prognostic factor for the response to curative effect radiotherapy in LAHNSCC patients. Nevertheless, metastatic lymph nodes are a prognostic factor for the response to curative effect radiotherapy in LAHNSCC patients. Patients with smaller lymph nodes have better local control.