Background: Information on the risks of herpes zoster (zoster) preceding a cancer diagnosis and the role of cancer treatment on risk is limited.

Methods: This was a prospective cohort of 241497 adults, with mean age 62.0 years at recruitment (2006-2009), linked to health datasets from 2006 to 2015. The relation between cancer diagnosis, treatment, and zoster risk was analyzed using time-varying proportional hazards models.

Results:  Over 1760 481 person-years of follow-up, 20286 new cancer diagnoses and 16350 zoster events occurred. Participants with hematological and solid cancer had higher relative risks of zoster than those without cancer (adjusted hazard ratio [aHR], 3.74 [95% confidence interval {CI}, 3.11-4.51] and 1.30 [95% CI, 1.21-1.40], respectively). Compared to those without cancer, zoster risk was also elevated prior to a hematological cancer diagnosis (aHR for 1-2 years prior, 2.01 [95% CI, 1.31-3.09]), but this was not the case for solid cancers (aHR for 1-2 years prior, 0.90 [95% CI, .75-1.07]). Compared to those without cancer, zoster risk among participants with solid cancers receiving chemotherapy was greater than in those without a chemotherapy record (aHR, 1.83 [95% CI, 1.60-2.09] and 1.16 [95% CI, 1.06-1.26], respectively).

Conclusions: For hematological cancer, increases in zoster risk are apparent in the 2 years preceding diagnosis and treatment; for solid organ cancers, the increased risk appears to be largely associated with receipt of chemotherapy.