Prognostication of serial post-intensity-modulated radiation therapy undetectable plasma EBV DNA for nasopharyngeal carcinoma
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Victor Ho-Fun Lee1, Dora Lai-Wan Kwong1, To-Wai Leung1, Cheuk-Wai Choi1, Vincent Lai2, Lydia Ng3, Ka-On Lam1, Sherry Chor-Yi Ng1, Chun-Kin Sze1, Chi-Chung Tong1, Patty Pui-Ying Ho1, Wing-Lok Chan1, Lai-San Wong1, Dennis Kwok-Chuen Leung1, Sum-Yin Chan1, Pek-Lan Khong2
1Department of Clinical Oncology, Queen Mary Hospital, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
2Department of Diagnostic Radiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Hong Kong
3Department of Radiation Oncology, University of Southern California, Los Angeles, California, USA
Victor Ho-Fun Lee, email: firstname.lastname@example.org
Keywords: intensity-modulated radiation therapy, nasopharyngeal carcinoma, non-metastatic, plasma EBV DNA, prognostic factors
Received: June 30, 2016 Accepted: November 22, 2016 Published: December 24, 2016
Plasma Epstein-Barr virus (EBV) DNA titers have been used to monitor treatment response and provide prognostic information on survival for nasopharyngeal carcinoma (NPC). However, the long-term prognostic role of pretreatment and posttreatment titers after radical contemporaneous radiation therapy remains uncertain. We recruited 260 evaluable patients with non-metastatic NPC treated with radical intensity-modulated radiation therapy (IMRT) with or without adjunct chemotherapy. Plasma EBV DNA titers at baseline and then 8 weeks and 6 months after IMRT were measured. Cox regression models were employed to identify interaction between post-IMRT 8th week and 6th month undetectable titers and 3-year survival endpoints. Concordance indices (Ct) from time-dependent receiver-operating characteristics (TDROC) were compared between patients with post-IMRT undetectable and those with detectable titers. After a median follow-up duration of 3.4 years (range 1.4-4.6 years), patients with post-IMRT 8th week and 6th month undetectable plasma EBV DNA titers enjoyed longer 3-year survival endpoints than those who had detectable titers at the same time points. Post-IMRT 8th week, and more significantly, post-IMRT 6th month undetectable plasma EBV DNA were the only significant prognostic factors of 3-year survival endpoints. Ct values for all 3-year survival endpoints for both post-IMRT 8th week and 6th month undetectable plasma EBV DNA were significantly higher in those with stage IVA–IVB diseases compared to stage I-III counterparts. Early post-IMRT undetectable plasma EBV DNA titers were prognostic of 3-year survival endpoints in patients with non-metastatic NPC. Intensified treatment should be further explored for patients with persistently detectable titers after IMRT.
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