Risk of Stroke in Nasopharyngeal Cancer Survivors: A National Registry-Based Population Cohort Study.

Background We aim to determine the risk of stroke and death within 30 days post stroke in nasopharyngeal cancer (NPC) survivors. Methods We conducted a population-based cohort study of patients diagnosed with NPC from Jan 1, 2005 to Dec 31, 2017. Using the cancer and stroke disease registries and the Singapore general population as the reference population, we report the age-standardized incidence rate differences (SIRDs) ratios (SIRs) and the cumulative incidence of stroke and the standardized mortality rate differences (SMRDs) and ratios (SMRs) for all causes of death within 30 days post stroke for NPC survivors. Findings At a median follow up of 48.4 months (IQR 19.8 – 92.9) for 3849 patients diagnosed with NPC, 96 patients developed stroke. The overall SIRD and SIR for stroke was 3.12 (95% CI 2.09 – 4.15) and 2.54 (95% CI 2.08 – 3.10) respectively. The SIRD was highest for the age group 70 – 79 years old (8.84 cases per 1000 person-years (PY); 0.46 – 17.21) while the SIR was highest for the age group 30 – 39 years old (16.41; 6.01 – 35.82). The SIRD and SIR for stage 1 disease was (6.96 cases per 1000 PY; 2.16 – 11.77) and (4.15; 2.46 – 7.00) respectively. The SMRD and SMR for all cause deaths within 30 days of stroke was (3.20 cases per 100 persons; -3.87 – 10.28) and (1.34; 0.76 – 2.37) respectively. Interpretation The overall risk of stroke was markedly elevated in survivors of NPC, especially in Stage 1 disease when compared to the general population. The risk of death within 30 days of stroke was not significantly higher for NPC survivors. Classification of Evidence This study provides Class II evidence of the increased risk of stroke in survivors of nasopharyngeal cancer compared to general population.