Neoplasms in neurofibromatosis 1 are related to gender but not to family history of cancer

The risk of malignancies among persons with neurofibromatosis 1 (NF1) is hi gher than in the general population, but the excess risk has not been preci sely estimated. The effects of gender and inheritance pattern on cancer ris k are unclear. Therefore, we conducted a historical cohort study to determi ne cancer risk factors by contacting 138 Caucasian NF1 patients originally seen at Baylor College of Medicine (BCM) in Houston between 1978 and 1984. A total of 304 patients of all ethnic groups were evaluated at BCM during t his period. We successfully located 173 patients, 138 of who were Caucasian . We computed standardized incidence ratios (SIRs) with the age-, gender-, and time period-specific rates from the Connecticut Tumor Registry for 2,09 4 person-years of observation (median follow-up = 16 years). Eleven inciden t tumors were reported. Females were at much higher risk of cancer than mal es (SIR = 5.6, 95% confidence interval (CI) 2.7-10.3 and SIR = 0.6; 95% CI, 0.0-3.0, respectively). We found no elevated cancer risk in unaffected fir st-degree relatives, regardless of whether the proband had cancer or not (S LR = 1.1 95% CI, 0.6-1.8 and SIR = 1.0, 95% CI, 0.6-1.5, respectively). Our results suggest that malignancy in the proband is not the result of a modi fying gene that has a significant impact on general cancer risk. Genet. Epi demiol. 20:75-86, 2001. (C) 2001 Wiley-Liss, Inc.