Association of delayed chemoradiotherapy with elevated Epstein-Barr virus DNA load and adverse clinical outcome in nasopharyngeal carcinoma treatment during the COVID-19 pandemic: a retrospective study

Table 2 Summary of multivariable analysis of prognostic factors for EBV DNA elevation and DFS

Endpoint	Variable	HR	95% CI	P value*
EBV DNA elevation	RT delay (≥ 6 vs. < 6 days)	7.08	2.53–19.88	< 0.001
	Pre-DNA (≥ 2000 vs. <2000 copies/ml)	2.17	0.88–5.32	0.092
DFS	RT delay (≥ 6 vs. < 6 days)	3.61	1.37–9.50	0.009

Abbreviations: RT, radiotherapy; Pre-DNA, pretreatment EBV DNA; DFS, disease-free survival; HR, hazard ratio; CI, confidence interval
* P-values were calculated using an adjusted Cox proportional hazards model; the following concerned prognostic variables were included in the analysis of EBV DNA elevation: age (≥ 45 vs. <45 years), sex (female vs. male), T category (T3-4 vs. T1-2), N category (N2-3 vs. N0-1), pretreatment EBV DNA (≥ 2000 vs. <2000 copies/ml), induction chemotherapy (yes vs. no), and RT delay (≥ 6 vs. < 6 days). In analysis of DFS, chemotherapy delay (≥ vs. < 10 days) was also included. Insignificant factors were excluded from the model and were not shown in the results

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