Are relatives of patients with multiple HNPCC spectrum tumours at increased risk of cancer?

BACKGROUND: Relatives of patients with early onset colorectal cancer, a feature of hereditary non-polyposis colorectal cancer (HNPCC), are at increased risk of colorectal cancer. AIMS: To investigate risk in relatives of patients with multiple primary cancers, another feature of HNPCC.
METHODS: Details were obtained on patients from one region who had developed colorectal cancer and a separate primary from the HNPCC tumour spectrum (colorectal, stomach, urinary, ovary, endometrial). Overall, 157 patients had second primaries occurring between 1990 and 1995 and 128 completed family histories were obtained by structured interview (study group). A comparison group of 444 patients with a single colorectal cancer were similarly interviewed.
RESULTS: Fifteen families (13%) from the study group were suggestive of HNPCC compared with three (0.7%, p<0.0001) from the comparison group. Overall risk of colorectal cancer in close relatives of the study group was 3.4 times the general population rate compared with 1.8 times for the comparison group. Bowel cancer risk was even higher for relatives of bowel/ovary and bowel/endometrial subgroups, but was similar to the comparison group for the bowel/bowel subgroup. Finally, extracolonic HNPCC associated cancers were seen twice as frequently as expected in the general population in relatives of the study group.
CONCLUSION: This study highlights the importance of taking a family history in patients with multiple primary cancers and indicates the risk of malignancy in their relatives.