Prostate cancer family history: count uncles and grandfathers on both sides

Design

Nationwide three-generation family cohort, Sweden

Population

Men under 69 in the third generation of the Swedish family-cancer database

Primary outcome

Familial relative risk of prostate cancer (standardised incidence ratio)

Effect

Two brothers SIR 4.1; plus an uncle or grandfather 10.1; maternal uncle 1.8, paternal uncle 1.5

A Swedish nationwide three-generation study in BJU International (published 1 October) calculated familial risks of prostate cancer for men under 69 according to which relatives had been diagnosed, including second-degree relatives (uncles and grandfathers) on both the maternal and paternal sides.

Two affected brothers carried a standardised incidence ratio (SIR) of 4.1, rising to 10.1 when an uncle or grandfather was also affected. An affected father gave an SIR of 3.1, rising to 4.7 with one affected second-degree relative and up to 11.5 with more. A grandfather alone gave about 1.6, and uncles 1.5 to 1.8, with maternal and paternal relatives equally informative. The highest risk, 27, was in men with affected brothers, father and two second-degree relatives.

Family history for prostate cancer is often taken as father or brother only, and on the father's side by instinct. Asking about uncles and grandfathers on both sides identifies more men at raised risk, particularly younger men whose fathers may not yet be old enough to be diagnosed. Whether to start PSA testing earlier remains a guideline and shared decision.

• Ask about prostate cancer in uncles and grandfathers on both the mother's and father's sides, not only father and brothers.
• Recognise that multiple affected relatives across generations can raise risk around ten-fold or more.
• Consider earlier discussion of PSA testing for men with a strong multigenerational family history, in line with local guidance.
• Consider genetic counselling referral for families with several affected men or early-onset disease.

Why it matters

The maternal side of the family is routinely skipped, yet it carried the same information as the paternal side.

Don't overread it

Standardised incidence ratios describe diagnosis rates, which can be inflated by more testing in men with a family history.

The statistics, in plain English

A standardised incidence ratio of 4.1 means four times the expected number of diagnoses compared with men of the same age without that family history. Part of the excess may reflect affected families being tested more often.

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