Rectal cancer in hereditary nonpolyposis colorectal cancer

Background: Hereditary nonpolyposis colorectal cancer (HNPCC) accounts for approximately 2% to 5% of all colorectal cancers. Rectal cancer in HNPCC is not well characterized. Methods: A retrospective medical record review of HNPCC patients with color ectal cancer diagnosis from December 1948 to December 1999 was performed in an attempt to elucidate the natural history of rectal cancer in HNPCC. Gro up A consisted of patients diagnosed with rectal cancer as the index colore ctal cancer. Group B consisted of patients diagnosed with rectal cancer as a metachronous colorectal cancer. Results: Twenty-five of 104 patients developed rectal cancer in our HNPCC r egistry. There were 18 patients in group A with a median age at diagnosis o f rectal cancer of 48 years (range 24 to 79) and 7 patients in group B diag nosed at a median age of 58 years (range 45 to 68). Three of 18 patients (1 7%) in group A developed metachronous colon cancers at a median of 203 mont hs (range 27 to 373) from the index rectal cancer. Rectal cancer in group B was diagnosed at a median 245 months (range 51 to 564) from the index colo rectal cancer diagnosis. Conclusions: Rectal cancer in HNPCC is not uncommon. The presentation of re ctal carcinoma should not obviate the evaluation for HNPCC in suspected cas es. (C) 2001 Excerpta Medica, Inc. All rights reserved.