Parasitic infections, antiparasitic drug exposure, and cancer risk: a systematic review and meta-analysis

Parasitic infections remain highly prevalent worldwide and contribute substantially to chronic morbidity in endemic regions. Increasing evidence suggests that certain parasites are etiologically linked to human malignancies, while the long-term oncologic impact of antiparasitic drug exposure remains uncertain. This systematic review and meta-analysis aimed to evaluate associations between parasitic infections, antiparasitic drug exposure, and cancer risk. A comprehensive search of PubMed/MEDLINE, Embase, Web of Science, and Scopus was conducted from inception to December 2025. Observational studies reporting associations between confirmed parasitic infection or antiparasitic drug exposure and incident cancer were included. Random-effects meta-analyses were performed where comparable effect estimates were available. Fifty-two studies met inclusion criteria, of which twenty-eight were eligible for quantitative synthesis. Liver fluke infection (Opisthorchis viverrini and Clonorchis sinensis) was strongly associated with cholangiocarcinoma (pooled OR 4.82; 95% CI 3.21–7.24). Chronic Schistosoma haematobium infection was significantly associated with bladder cancer (pooled OR 3.17; 95% CI 2.11–4.76), with a stronger association observed for squamous cell carcinoma. The association between Schistosoma mansoni and colorectal cancer was modest and not statistically significant (pooled OR 1.42; 95% CI 0.98–2.06). In contrast, pooled analyses of antiparasitic drug exposure—including praziquantel, albendazole/mebendazole, and ivermectin—demonstrated no increased overall cancer risk. Heterogeneity across studies was moderate for infection-related analyses and low for drug exposure analyses. These findings confirm strong associations between specific parasitic infections and site-specific malignancies, consistent with established carcinogenic classifications. Evidence for other parasite–cancer links remains inconclusive. Importantly, therapeutic antiparasitic drug exposure does not appear to increase long-term cancer risk. Effective control and treatment of carcinogenic parasitic infections should be considered an integral component of global cancer prevention strategies.