Mutant alleles of several genes in the DNA repair pathway have been found to predispose women to breast cancer. From a public health perspective, the importance of a given allele in a population is determined by the frequency of the allele and by the relative risk of breast cancer that it confers. In Poland founder alleles of the BRCA1, CHEK2 and NBS1 genes have been associated with an increased risk of breast cancer, but the relative contribution of each of these alleles to the overall breast cancer burden has not yet been determined. We screened 2012 unselected cases of breast cancer and 4000 population controls for 7 different mutations in these genes. Overall, a mutation was found in 12% of the cases and in 6% of the controls. Mutations in BRCA1 and CHEK2 contributed in approximately equal measure to the burden of breast cancer in Poland. A BRCA1 mutation was present in 3% of the cases. The missense BRCA1 mutation C61G was associated with a higher odds ratio for breast cancer (OR=15) than were either of the truncating BRCA1 mutations 4153delA (OR=2.0) and 5382insC (OR=6.2). In contrast, a higher odds ratio was seen for truncating CHEK2 mutations (OR=2.1) than for the missense mutation I157T (OR=1.4). This study suggests that cancer risks may be specific for particular alleles of a susceptibility gene and that these different risks should be taken into account by genetic counselors.

Background: A common missense variant of the CDKN2A gene (A148T) predisposes to malignant melanoma in Poland. An association between malignant melanoma and breast cancer has been reported in several families with CDKN2A mutations, Objective: To determine whether this variant also predisposes to breast cancer. Methods: Genotyping was undertaken in 4209 cases of breast cancer, unselected for family history, from 18 hospitals throughout Poland and in 3000 controls. Results: The odds ratio (OR) associated with the CDKN2A allele for women diagnosed with breast cancer before the age of 50 was 1.5 (p = 0.002) and after age 50 it was 1.3 (p = 0.2). The effect was particularly strong for patients diagnosed at or before the age of 30 (OR = 3.8; p = 0.0002).Conclusions: CDKN2A appears to be a low penetrance breast cancer susceptibility gene in Poland. The association should be confirmed in other populations.

We identified 4316 unselected incident cases of early-onset breast cancers (<51 ears of age at diagnosis) in 18 Polish hospitals between 1996 and 2003. We were able to obtain a blood sample for DNA analysis from 3472 of these (80.4%). All cases were tested for the presence of three founder mutations in BRCA1. The proportion of cases with a BRCA1 mutation was 5.7%. The hereditary proportions were higher than this for women with breast cancer diagnosed before age 40 (9%), for women with cancer of medullary or atypical medullary histology (28%), for those with bilateral cancer (29%) or with a family history of breast or ovarian cancer (13%). It is reasonable to offer genetic testing to women with early-onset breast cancer in Poland.

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Evidence to date that germline mutations in the tumor suppressor gene BRCA1 increase the incidence of colorectal cancer is mixed, and both positive and negative results have been reported. To establish whether or not inherited variation in BRCA1 influences the risk of colorectal cancer, we genotyped 2,398 unselected patients with colorectal cancer and 4,570 controls from Poland for three BRCA1 founder mutations (C61G, 4153delA and 5382insC). A BRCA1 mutation was present in 0.42% of unselected cases of colorectal cancer and in 0.48% of controls (OR = 0.8; P = 0.8). The mutation frequency was slightly higher (0.93%) in 321 cases who reported a family history of colon cancer in a first- or second-degree relative (OR = 1.9; P = 0.5). A BRCA1 mutation was also seen in excess (0.82%) in 851 cases who were diagnosed with colorectal cancer at age 60 or earlier (OR = 1.7; P = 0.3). The mean age at onset in carriers was 7 years younger than in non-carriers (57.0 years vs. 64.0) and the difference was significant (P = 0.05). This study suggests that BRCA1 mutations may be associated with early-onset of colorectal cancer.