Efficacy of continuous, daily, oral, ultra-low-dose 200 mg acyclovir to prevent herpes zoster events among bortezomib-treated patients: a report from retrospective study.

OBJECTIVE: Herpes zoster is the most common infection in patients treated with bortezomib-containing regimens for multiple myeloma. Some clinical trials have reported on the use of acyclovir prophylaxis to decrease the incidence of herpes zoster. However, the appropriate acyclovir dose and duration of prophylaxis remain unclear. The primary objective of this study was to evaluate the efficacy of continuous oral 200 mg/day acyclovir prophylaxis and the secondary objective was to determine the risk factors for developing herpes zoster.
METHODS: We collected medical information from consecutive patients who received bortezomib with or without acyclovir prophylaxis for relapsed or refractory multiple myeloma at our hospital and retrospectively analyzed the efficacy of acyclovir prophylaxis and the parameters for predicting the risk factors for developing herpes zoster. The definition of acyclovir prophylaxis was oral continuous administration of 200 mg of once daily, without cessation, during the entire period of bortezomib treatment.
RESULTS: Six of the 33 patients in the study developed herpes zoster during bortezomib treatment. No varicella-zoster virus reactivation was observed in the 19 patients in the acyclovir prophylaxis group. The incidence of herpes zoster was significantly higher in the group that did not receive acyclovir prophylaxis (43%, 6 of 14 patients) than in the group that did (0%, 0 of 19; P = 0.003). The predictive factors for varicella-zoster virus reactivation were male sex (P = 0.035) and the use of acyclovir (P = 0.003).
CONCLUSIONS: Continuous prophylaxis by oral 200 mg/day acyclovir in multiple myeloma patients receiving bortezomib treatment is effective and sufficient in preventing herpes zoster.