Prognostic and Predictive Factors
Breast cancer is commonly treated by various combinations of surgery, radiation therapy, chemotherapy, and hormone therapy. Prognosis and selection of therapy may be influenced by the following clinical and pathology features (based on conventional histology and immunohistochemistry):
- The age and menopausal status of the patient.
- The stage of the disease.
- The histologic and nuclear grade of the primary tumor.
- The ER and PR status of the tumor.
- Human epidermal growth factor type 2 receptor (HER2/neu) overexpression.
- Proliferative capacity of the tumor (e.g., Ki67).
Molecular profiling has led to classification of breast cancer into the following five distinct subtypes:[17,18]
- Luminal A.
- Luminal B.
The use of molecular profiling in breast cancer includes the following:[17,18]
- ER and PR status testing.
- HER2/neu receptor status testing.
- Gene profile testing by microarray assay or reverse transcription-polymerase chain reaction (e.g., MammaPrint, Onco type DX).
Although certain rare inherited mutations, such as those of BRCA1 and BRCA2, predispose women to develop breast cancer, prognostic data on BRCA1 /BRCA2 mutation carriers who have developed breast cancer are conflicting; these women are at greater risk of developing contralateral breast cancer. Since criteria for menopausal status vary widely, some studies have substituted age older than 50 years as a surrogate for the postmenopausal state. Breast cancer is classified into a variety of histologic types, some of which have prognostic importance. For example, favorable histologic types include mucinous, medullary, and tubular carcinoma.[19,20,21]
Pathologically, breast cancer can be a multicentric and bilateral disease. Bilateral disease is somewhat more common in patients with infiltrating lobular carcinoma. Patients who have breast cancer should have bilateral mammography at the time of diagnosis to rule out synchronous disease. The role of magnetic resonance imaging (MRI) in screening and follow-up continues to evolve. Having demonstrated an increased detection rate of mammographically occult disease, the selective use of MRI for additional screening is being used with increased frequency despite the absence of randomized, controlled data. Because only 25% of MRI-positive findings represent malignancy, pathologic confirmation prior to treatment action is recommended. Whether this increased detection rate will translate into improved treatment outcome is unknown.[22,23,24] When BRCA1 /BRCA2 mutation carriers were diagnosed at a young age, the risk of a contralateral breast cancer reached nearly 50% in the ensuing 25 years.[25,26]