Authors have defined "Cancer Frequent Family (CFF)" as a family that presents with clustering of different types of cancers among its members, but does not satisfy the criteria of any known hereditary cancer syndromes. The inclusion criteria for
CFF
are: three or more cancer patients ①among siblings or ② in more than two successive generations or ③in 3 or more cousins, with at least one of the patients diagnosed before the age of 50. Gastric cancer after age of 45 and primary liver cancer
were
excluded. By screening family history of cancer patients admitted to Seoul National University Hospital since 1992, nine families fulfiling the CFF criteria were identified. Among 294 family members from these 9 families, thirty-six(12%) were
affected
with cancer. A total of 41 primary cancers affecting 10 different organs were found, with the average age at diagnosis of the first primary cancer being 47. Five members were affected with double primary cancers; four with 2 colorectal cancers
and
one
with a rectal cancer and a malignant thymoma. Colorectal cancer was by far the most common malignancy encountered, accounting for 51% of all the malignancies found. The average age at diagnosis of colorectal cancers in CFF was significantly
younger
than
that of sporadic cases(43 vs. 56, p<0.01). The incidence of metachronous colorectal cancer was also high(24%) in this group. On the basis of familial aggregation, younger age of onset, and multiplicity of tumor in affected individuals, hereditary
backgrounds can be suspected in colorectal cancer patients of CFF families. Our results indicate that clustering of different malignancies in a family may suggest possible hereditary causes and that regular screening may aid in the early
detection
of
other affected individuals in CFF families.
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