Five-year interval for prostate sufficient, NCI (National Cancer Institute) suggests:

The American Society of Clinical Oncology (ASCO) meeting last month heard that annual screening of US men over 50 for prostate cancer may be reduced to once every five years in certain cases. Men who show a low PSA level need not worry that this will increase markedly within a year, the University of Colorado's Health Sciences Center's David Crawford said at the meeting. Quoting National Cancer Institute (NCI) data, he said that 98.8% of surveyed males aged 55-74 who recorded a low PSA rate remained at a low rate four years later. Some urologists and other groups view the screening procedure as uncomfortable. Increasing the interval, where safe to do so, could also save the US health system $1bn annually, said Dr Crawford.