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We investigated the risk of prostate cancer in relation to a family history of prostate cancer in 58,279 men ages 55–69 years. We found 704 incident cases after 6.3 years of follow-up. Rate ratios and 95 confidence intervals for having an affected vsnonaffected father and brother were, respectively 1.44 (0.80–2.58) and 5.57 (1.61–19.26). We found no evidence for an increasing risk with an increasing percentage of affected family members. The associations we observed were stronger for cases diagnosed before age 70 compared with cases diagnosed after age 70 and for advanced compared with localized tumors.

Within a prospective cohort study on diet and cancer, information was collected on cancer prevalence and baseline meat consumption. A nested case-control study on meat and cancer was conducted with 656 prevalent colorectal cases, 1,894 breast cancer cases, and 4,701 controls. When analyzed cross-sectionally, prevalence odds ratios for eating meat rarely versus regularly were 2.08 for female colorectal and 1.75 for breast cancer. In the longitudinal analysis, cases who started consuming meat rarely after diagnosis were excluded, resulting in odds ratios of 0.51 for female colorectal and 1.17 for breast cancer. These opposite findings highlight the problem of cross-sectional designs