Insights into breast cancer: New familial patterns and identification of a potential predictive marker

Abstract: The last proportion of heredity in breast cancer has proven to be somewhat elusive despite massive attempts to identify the associated factors. Approximately 50 percent of breast cancer caused by familial factors is currently explained. The five-year survival for breast cancer patients is excellent; however, breast cancer is considered a chronic disease, and given enough time, new tumors can develop. Women age 40 and older are offered screening mammography. However, population screening is expensive, and being able to pinpoint those who are at high risk of breast cancer would be beneficial. Both genetic and environmental risk factors could be used to select women who need screening. A major aim of this thesis was to try to identify potential familial patterns as candidates for hereditary breast cancer. In Paper I, we studied horizontal family history of breast cancer in relation to histology to discover a candidate phenotype for recessive inheritance. A horizontal pedigree pattern is characterized by two or more sisters diagnosed with breast cancer, without a family history of breast cancer in prior generations. A horizontal inheritance was more common in patients with tubular carcinoma compared with other histologic subtypes. Therefore, we propose that breast cancer patients with tubular carcinoma who have a sister or sisters diagnosed with breast cancer are candidates for genetic studies when searching for a recessively inherited predisposing gene. In paper II, we studied the occurrence of cancer in first-degree relatives of breast cancer patients diagnosed with the lobular carcinoma histologic subtype compared with other histological subtypes of breast cancer. We found a hereditary pattern involving breast cancer patients with lobular carcinoma and having a father diagnosed with cancer. The association was independent of a family history of breast cancer in sisters, the mother and grandmothers. Similarly, even though prostate cancer was prominent in the fathers, the association remained after removal of fathers diagnosed with prostate cancer. In paper III, we confirmed a previously reported younger age at breast cancer diagnosis in carriers of a BRCA1 mutation of paternal origin compared with maternal origin. Additionally, we observed an older age at ovarian cancer diagnosis in carriers of a BRCA1 mutation of paternal origin compared with maternal origin. No such observations were observed for BRCA2 mutation carriers. In paper IV, we studied the occurrence of spider telangiectasias at the time of breast cancer diagnosis in relation to hormonal risk factors. We reported that the occurrence of spider telangiectasias was associated with several hormonal risk factors such as weight, parity, history of oral contraceptive use, and menopausal hormone therapy use. A better overall survival was observed in older breast cancer patients who displayed spider telangiectasias at the time of breast cancer diagnosis.