Min Kang1, Pingting Zhou2, Xueyin Liao1, Meng Xu1, Rensheng Wang3. 1. Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University, Nanning 530021, Guangxi, PR China. 2. Department of Radiation Oncology, People's Hospital of Guangxi Zhuang Autonomous Region, Nanning 530021, Guangxi, PR China. 3. Department of Radiation Oncology, The First Affiliated Hospital of Guangxi Medical University, Nanning 530021, Guangxi, PR China. Electronic address: 13807806008@163.com.
Abstract
BACKGROUND AND PURPOSE: In 2017, the 8th edition of the nasopharyngeal carcinoma (NPC) staging manual published by the Union for International Cancer Control/American Joint Committee on Cancer (UICC/AJCC) defined new rules regarding the involvement of anatomical masticatory muscles (MM). The purpose of this study is to evaluate the validity of the current T-staging system after the addition of revisions regarding MM involvement. METHODS: We performed a retrospective review of 608 patients, who were newly diagnosed with NPC and treated with intensity-modulated radiotherapy (IMRT) between January 2008 and March 2010. RESULTS: We found MM involvement in 398 NPC cases (65.4%). We observed a significant difference in overall survival (OS; 75.6% vs. 86.7%, P = .043) and in local relapse-free survival (LRFS; 81.5% vs. 88.6%, P = .048) between patients with and without MM involvement, but no difference in distant metastasis-free survival (DMFS; 80.3% vs. 85.0%, P = .147) or disease-free survival (DFS; 77.9% vs. 81.6%, P = .081). Significant differences in OS and LRFS were also found among different types of MM involvement. Compared with patients who had concurrent involvement of the lateral pterygoid muscle (LP), patients with tumors invading only the medial pterygoid muscle (MP) had a higher OS and LRFS rates, according to univariate and multivariate analysis (P < .05). CONCLUSIONS: MM involvement is an independent prognostic factor for OS and LRFS. We conclude that the decision to down-stage MP as T2 in the 8th edition staging system is valid. However, tumors with LP involvement were more rational classified into a higher T-staging category than tumors with only-MP involvement.
BACKGROUND AND PURPOSE: In 2017, the 8th edition of the nasopharyngeal carcinoma (NPC) staging manual published by the Union for International Cancer Control/American Joint Committee on Cancer (UICC/AJCC) defined new rules regarding the involvement of anatomical masticatory muscles (MM). The purpose of this study is to evaluate the validity of the current T-staging system after the addition of revisions regarding MM involvement. METHODS: We performed a retrospective review of 608 patients, who were newly diagnosed with NPC and treated with intensity-modulated radiotherapy (IMRT) between January 2008 and March 2010. RESULTS: We found MM involvement in 398 NPC cases (65.4%). We observed a significant difference in overall survival (OS; 75.6% vs. 86.7%, P = .043) and in local relapse-free survival (LRFS; 81.5% vs. 88.6%, P = .048) between patients with and without MM involvement, but no difference in distant metastasis-free survival (DMFS; 80.3% vs. 85.0%, P = .147) or disease-free survival (DFS; 77.9% vs. 81.6%, P = .081). Significant differences in OS and LRFS were also found among different types of MM involvement. Compared with patients who had concurrent involvement of the lateral pterygoid muscle (LP), patients with tumors invading only the medial pterygoid muscle (MP) had a higher OS and LRFS rates, according to univariate and multivariate analysis (P < .05). CONCLUSIONS: MM involvement is an independent prognostic factor for OS and LRFS. We conclude that the decision to down-stage MP as T2 in the 8th edition staging system is valid. However, tumors with LP involvement were more rational classified into a higher T-staging category than tumors with only-MP involvement.