Department of Health Evaluation Sciences, Pennsylvania State University College of Medicine, Hershey, Pennsylvania, USA. jmuscat@psu.edu

Talc, like asbestos, is a silicate that has been studied in relation to cancer risk. Several studies conducted over the past 25 years found an association between perineal talc powders and ovarian cancer. The summary relative risk is about 1.3 (95% confidence intervals 1.2-1.5) and these data have been interpreted as supporting a causal role. In this review article, we discuss the chemical and morphological features of talc and asbestos, and explain why despite their similar chemical classification talc does not possess asbestos-like carcinogenic properties. The heterogeneity in the perineal dusting studies has raised important concerns over the validity of the exposure measurements, and the lack of a consistent dose-response effect limits making causal inferences. Perhaps more importantly, whereas it is unknown whether external talc dust enters the female reproductive tract, measures of internal talc exposure such as talc-dusted diaphragms and latex condoms show no relationship with ovarian cancer risk. In addition, the therapeutic use of high dose cosmetic grade talc for pleurodesis has not been shown to cause cancer in patients receiving these treatment modalities. Talc is not genotoxic. Mechanistic, pathology and animal model studies have not found evidence for a carcinogenic effect. In summary, these data collectively do not indicate that cosmetic talc causes ovarian cancer.

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M. D. Anderson Cancer Center, Houston, TX, USA.

OBJECTIVE: The unique characteristics of cancer, particularly issues involving the use of surrogate endpoints in clinical trials, present special challenges in the development of cancer drugs. In response, the U.S. Food and Drug Administration (FDA) has partnered with the American Society of Clinical Oncology, the American Association for Cancer Research, and the American Society of Hematology to conduct public workshops evaluating potential endpoints for drug approvals for the most common tumor types. METHODS: A workshop evaluating potential endpoints in ovarian cancer drug research was held in Bethesda, Maryland, in April 2006. Invited experts presented research findings and discussed endpoints in trials of drugs for treatment of Stage III and IV ovarian cancer. RESULTS: The panel responded to specific questions from FDA, discussing use of progression-free survival as a surrogate for overall survival and use of CA-125 levels as an indicator of response. Panel members also addressed endpoints in first-line therapy, second-line and subsequent therapy, and maintenance therapy. CONCLUSION: Expert commentary provided by panel members will inform FDA’s draft guidance on clinical endpoints for cancer drug approvals and will be discussed at meetings of the FDA’s Oncologic Drugs Advisory Committee. FDA intends to develop a set of principles that can be used to define efficacy standards for drugs used to treat ovarian and other cancers.

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