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 higher than in the general population, but the excess risk has not been precisely estimated. The effects of gender and inheritance pattern on cancer risk are unclear. Therefore, we conducted a historical cohort study to determine 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 this 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 2,094 person-years of observation (median follow-up = 16 years). Eleven incident tumors were reported. Females were at much higher risk of cancer than males (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 first-degree relatives, regardless of whether the proband had cancer or not (SIR = 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 modifying gene that has a significant impact on general cancer risk. Copyright 2001 Wiley-Liss, Inc.