Eleven studies (222 participants in the intervention groups and 399 in the control groups) were included in the review: 2 randomised controlled trials (n=102), 5 prospective cohorts (4 with historical controls) (n=425) and 4 retrospective cohorts (n=94).
Most of the studies scored 4 or 5 points for quality out of a possible 7. All studies had a control group and clearly defined objectives and interventions, ten had clearly defined outcome measures, six had clear inclusion and exclusion criteria, only two described withdrawals and drop-outs, and none described a method for assessing adverse events.
The intervention group was significantly less likely to experience HBV reactivation (10 studies) than the control group (RR 0.13, 95% CI: 0.07, 0.24, p<0.01; ARR -0.46, 95% CI: -0.61, -0.31, p<0.01). The NNT to prevent one reactivation was 3. There was no statistical heterogeneity associated with this finding (I2=0%). The results were similar, showing significant benefit for the intervention group, when the studies were stratified by the type of malignancy; there were 4 studies of patients with solid tumours (RR 0.13, 95% CI: 0.05, 0.34, p<0.01; ARR -0.32, 95% CI: -0.43, -0.22, p<0.01) and 4 studies of patients with haematological malignancies (RR 0.09, 95% CI: 0.03, 0.31, p<0.01; ARR -0.70, 95% CI: -0.92, -0.48, p<0.01).
Reactivation-related liver mortality (9 studies) was significantly less common in the intervention group than in the control group (RR 0.30, 95% CI: 0.1, 0.94, p=0.04; ARR -0.03, 95% CI: -0.07, 0.00, p=0.04). There was no statistically significant difference between the groups when the studies were stratified by the type of malignancy (solid or haematological), though there were no deaths in either intervention group (0 out of 63 and 0 out of 39) whereas there were deaths in the control groups (3 out of 67 and 2 out of 51).
There was no statistically significant difference between the groups for overall mortality (8 studies), either overall or when stratified by the type of malignancy.
Treatment delays were evaluated in 4 studies. When 3 studies were pooled, there were significantly less treatment delay or premature cessation of chemotherapy related to HBV reactivation in the intervention group than in the control group (RR 0.08, 95% CI: 0.02, 0.34, p<0.01; ARR -0.21, 95% CI: -0.43, 0.00, p=0.05). The pooling of 3 studies that reported treatment delays and premature cessation of chemotherapy for all causes also found a significant benefit for the intervention group (RR 0.41, 95% CI: 0.27, 0.63, p<0.01; ARR -0.24, 95% CI: -0.33, -0.15, p<0.01).