Recent studies suggest that there are groups of genes that predispose simultaneously to both early-onset breast and laryngeal cancer. Studies were performed on a large series of unselected patients with laryngeal cancer diagnosed in Szczecin, Poland. Pedigrees of 683 laryngeal cancer patients were analysed for the frequency of early-onset and late-onset breast cancer among first degree relatives. The observed frequencies of breast cancer in these families were compared to those expected. In addition, common mutations/variants in the 3 genes BRCA1, NOD2 and CYP1B1, known to be associated with early-onset breast cancer, were assessed to determine their frequency in 348 unselected laryngeal cancers. The average age at diagnosis of LC among patients, who had relatives affected by BC diagnosed under the age of 50 years was 57.62. In comparison LC patients reporting a first degree relative affected by BC diagnosed above 50 years of age, had an average age of diagnosis of 66.00 years, which was significantly different (p=0.0064). Similarly, the average age of diagnosis of BC among patients with LC diagnosed under age of 50 years was 46.7 years and whereas LC patients with tumors diagnosed above 50 years had relatives diagnosed with breast cancer at an average age of 53.37 years, which was significantly different (p=0.02).
From the 348 consecutive ascertained laryngeal cancer patients who had molecular studies undertaken, breast cancers among first degree relatives were found in 18 families including 8 with breast cancers diagnosed less than 50 years of age. A molecular basis was identified (the CYP1B1 355T/T genotype) in only 2 of the 8 early cases suggestive of there being additional, as yet unknown genes that are associated with an early-onset laryngeal-breast cancer phenotype.