An epidemiologic perspective on biomarkers

Personalized medicine for osteoarthritis: where are we now?

Personalized medicine is a much talked about subject that is a timely and important development to healthcare in general and also specifically for patients affected by osteoarthritis. This review uses biomarker examples pertinent to osteoarthritis to highlight the current status of the field, while also highlighting probable future developments. It is not meant to be an exhaustive account. The BIPED(s) [Burden of disease, Investigative, Prognosis, Efficacy, Diagnosis (safety)] classification system is used to organize the discussion of examples. Biomarkers pertaining to burden, investigation, prognosis, efficacy, diagnosis and safety are highlighted. The examples are followed by a discussion of issues related to interpretation and application of biomarker results and approaches to solve the challenges interpretation faces, including graphical, mathematical and synthetic representations. Through this review, it is hoped that a better appreciation can be gained of the potential and pitfalls of personal medicine in the care of patients with osteoarthritis.

Biomarkers and environmental risk assessment: guiding principles from the human health field

Although the potential use of biomarkers within environmental risk assessment (ERA) has long been recognised their routine use is less advanced compared with clinical human health risk assessment, where a number of familiar biomarkers (such as blood pressure and serum cholesterol) are in common usage. We have examined how biomarkers are incorporated into human health risk assessment and have identified several 'required elements'. These include identification of the (clinical) assessment endpoint at the outset, rational selection of the biomarker(s) (the measurement endpoint), biomarker 'validation' (e.g. QA/QC) and biomarker 'qualification' (evidence linking the measurement and assessment endpoints). We discuss these elements in detail and propose that their adoption will facilitate the routine use of biomarkers in environmental risk assessment. Furthermore, our analysis highlights the need for cooperation between those working with biomarkers within human and environmental risk assessment to exchange best practice between common disciplines for mutual advantage.

Chemoprevention of human skin cancer

The incidence of skin cancer has been rising in recent years with significant effects on public health. Primary prevention has proven inadequate in impacting the incidence of skin cancer, thus stimulating the development of chemopreventive strategies. The majority of skin cancer chemoprevention studies focus on occurrence of new nonmelanoma skin cancers (NMSC) in individuals with a previous NMSC, or on reduction in the number of premalignant skin lesions such as actinic keratoses (AK). Dysplastic nevi, a likely precursor of melanoma, are also potential targets for chemoprevention strategies. Premalignant lesions are especially attractive as endpoints since they are more common than frank cancer, resulting in reduced sample size, length, and cost of clinical trials. Development of new agents that affect the pathogenesis of skin cancer will be discussed, from elucidation of molecular targets to implementation of trials designed to determine the effects of chemopreventive interventions on human skin cancer.

Complex ovarian cysts in postmenopausal women are not associated with ovarian cancer risk factors: preliminary data from the prostate, lung, colon, and ovarian cancer screening trial

OBJECTIVE

We assessed whether asymptomatic ovarian abnormalities detected on ultrasonography in postmenopausal women are precursors to ovarian cancer.

STUDY DESIGN

We compared the transvaginal ultrasonographic findings from the initial examination of 20,000 postmenopausal women enrolled to date in an ongoing randomized trial of cancer screening with data on the established risk factors for ovarian cancer obtained from self-administered questionnaires. We distinguished cysts with the suggestive characteristic(s) of a septum, a solid component, or an irregular or thick wall ("complex cysts") from simple sonolucent cysts with none of those features.

RESULTS

High parity, a strong ovarian cancer protective factor, was negatively associated with complex cysts (odds ratio for > or =5 births vs no births, 0.72; 95% confidence interval, 0.53-0.97), but long-term oral contraceptive use, another strong ovarian cancer protective factor, was not associated with complex cysts (odds ratio, 0.96; 95% confidence interval, 0.76-1.20). A family history of ovarian cancer or multiple breast cancers, a strong risk factor for cancer, was not associated with complex cysts (odds ratio, 0.99; 95% confidence interval, 0.68-1.44). Other abnormalities found on ultrasonography (including simple cysts, bilateral cysts, or all abnormalities combined) also did not share the established risk factors for ovarian malignancy. We did not identify any combination of features of abnormalities (septum, echogenicity, size, or papillary projections) that manifested the cancer risk factor profile.

CONCLUSIONS

Although a very small proportion of the clinically silent ovarian abnormalities found on ultrasonography are determined to be ovarian cancers, the remaining complex cysts and other clinically suspicious abnormalities do not appear to be the immediate precursors of ovarian cancer. The eventual identification of such precursors will yield opportunities for earlier diagnosis, screening of high-risk groups, and better understanding of the cause of this often lethal malignancy.

Phase III, large-scale chemoprevention trials. Approach to chemoprevention clinical trials and phase III clinical trial of tamoxifen as a chemopreventive for breast cancer--the US National Cancer Institute experience

Clinical trials to evaluate interventions for cancer prevention are designed as early (phase I, IIa, and IIb) or late-phase studies. Whereas the former are small and generally rely on intermediate endpoint biomarkers of carcinogenesis, the latter are large-scale, long-term, randomized, phase III studies that address endpoints such as cancer incidence. The Breast Cancer Prevention Trial, P-1, conducted by the National Surgical Adjuvant Breast and Bowel Project (NSABP), is discussed as an example of a large, extended, phase III trial designed to answer the question of whether tamoxifen reduces the incidence of breast cancer in women who are at increased risk for the disease.

A proposal for the establishment of scientific criteria for health claims for functional foods

Functional foods are defined and used differently in different nations. Health claims for these foods influence consumer behavior and potentially affect public health. In an increasingly global economy, health claims for functional foods should meet internationally agreed upon scientific criteria. The concept of health claims as it exists internationally is discussed, and suggestions to assist consumers, government, industry, and academia in deciding on a scientific and ethical basis for international agreement on health claims for functional foods are offered.

Cancer biomarkers in the field of tea

Suitable intermediate end-point biomarkers are needed in order to reduce the time and expense associated with cancer chemoprevention studies. Because of the multi-step nature of cancer intermediate biomarkers reflect a continuum of events associated with different stages of disease development, and range from genetic damage linked to cancer initiation, to tumor growth and expansion during disease progression. With tea, experimental evidence points to potential protection at several stages of carcinogenesis including endogenous carcinogen formation, carcinogen activation and detoxification, DNA damage and destabilisation, cell proliferation, neoplastic growth and metastatic spread. If used effectively in tea research, biomarkers should contribute to a better understanding of the possible extent of cancer protection afforded by tea, as well as the putative mechanisms involved and the principal components of tea with prophylactic potential.

Surrogate endpoints in chemoprevention of breast cancer: guidelines for evaluation of new biomarkers

Markers of early events in the development of breast cancer are potential candidates for surrogate endpoints in chemoprevention trials. There are many such markers and the challenge is to identify truly relevant markers. If successful, surrogate endpoints offer several potential benefits in the conduct of prevention trials, including: shorter latency and hence shorter trials; reductions in size and cost of trials; and the opportunity to study prevention measures where use of primary outcomes would be excessively invasive or unethical. Although there are currently no validated surrogate endpoints for breast cancer, criteria for the discovery and validation of surrogates have been proposed. Putative surrogate endpoints should be biologically plausible, represent an early event in the causal pathway, be measurable by a standardized and reliable assay, and exhibit a dose-response. Perhaps most importantly, surrogates should statistically capture the effect of the intervention on outcome. The identification and establishment of a biomarker as a valid surrogate for cancer is a stepwise process that involves both smaller "transitional" studies and larger second-generation chemoprevention trials in which both primary outcome and putative surrogates are measured. Transitional studies are used to move new markers from the laboratory into use in human populations, and are designed to address specific questions of assay validity, treatment/marker associations, marker/disease associations, and inter- and intra-individual variability. Promising markers should be added to current and planned, large, traditionally designed chemoprevention trials in order to definitively address the issues of optimal representation, and to test the adequacy with which the marker(s) captures the effect of treatment on outcome.(ABSTRACT TRUNCATED AT 250 WORDS)