A cluster-randomised, parallel group, controlled intervention study of genetic prostate cancer risk assessment and use of PSA tests in general practice--the ProCaRis study: study protocol.

INTRODUCTION

Unsystematic screening for prostate cancer (PCa) is common, causing a high number of false-positive results. Valid instruments for assessment of individual risk of PCa have been called for. A DNA-based genetic test has been tested retrospectively. The clinical use of this test needs further investigation. The primary objective is to evaluate the impact on the use of prostate-specific antigen (PSA) tests of introducing genetic PCa risk assessment in general practice. The secondary objectives are to evaluate PCa-related patient experiences, and to explore sociocultural aspects of genetic risk assessment in patients at high PCa risk.

METHODS AND ANALYSIS

The study is a cluster-randomised, controlled intervention study with practice as the unit of randomisation. We expect 140 practices to accept participation and include a total of 1244 patients in 4 months. Patients requesting a PSA test in the intervention group practices will be offered a genetic PCa risk assessment. Patients requesting a PSA test in the control group practices will be handled according to current guidelines. Data will be collected from registers, patient questionnaires and interviews. Quantitative data will be analysed according to intention-to-treat principles. Baseline characteristics will be compared between groups. Longitudinal analyses will include time in risk, and multivariable analysis will be conducted to evaluate the influence of general practitioner and patient-specific variables on future PSA testing. Interview data will be transcribed verbatim and analysed from a social-constructivist perspective.

ETHICS AND DISSEMINATION

Consent will be obtained from patients who can withdraw from the study at any time. The study provides data to the ongoing conceptual and ethical discussions about genetic risk assessment and classification of low-risk and high-risk individuals. The intervention model might be applicable to other screening areas regarding risk of cancer with identified genetic components, for example, colon cancer. The study is registered at the ClinicalTrials.gov (Identifier: NCT01739062).