Abstract / Summary
Background: This umbrella review aimed to systematically synthesize and critically appraise the available evidence from systematic reviews and meta-analyses evaluating the association between talc exposure and cancer risk in humans.
Methods: This umbrella review was conducted in accordance with the PRIOR guidelines and registered in PROSPERO. A comprehensive search of PubMed, Embase, Scopus, Web of Science, and Epistemonikos was performed up to October 2024 without language or date restrictions. Eligible studies were systematic reviews evaluating any type of talc exposure in humans. Study selection and data extraction were performed independently, and risk of bias was assessed using the AMSTAR-2 tool.
Results: Nine systematic reviews were included, eight combining cohort and case-control studies and one restricted to cohort studies. Cosmetic talc exposure was the most frequently investigated, with most reviews focused on ovarian cancer. Moderate overlap of study populations (9.2%) was identified, primarily related to Boon et al. Based on AMSTAR-2, confidence in the evidence was moderate in one review and critically low in seven, with frequent methodological shortcomings such as lack of protocol registration and unclear study exclusions. For occupational exposure, elevated risks were observed for overall cancer (RR 1.21; 95% CI 1.03-1.42) and colorectal cancer (SIR 1.59; 95% CI 1.07-2.26), while no increased risk was found for other cancer types. Four of five systematic reviews evaluating cosmetic talc exposure and ovarian cancer reported a statistically significant association with increased ovarian cancer risk, whereas one review found no statistically significant association. However, confidence in the results of the reviews included was predominantly low or critically low, reflecting important methodological limitations, including concerns regarding risk-of-bias assessment and reporting. Overall, the evidence supporting an association between cosmetic talc exposure and ovarian cancer was of limited confidence.
Conclusion: There is limited evidence from systematic reviews regarding the association of exposure to cosmetic talc with an increased risk of developing ovarian cancer. Therefore, the results of the systematic reviews should be regarded as suggestive, rather than definitive, and further studies are required to demonstrate a causal relationship.