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Proliferative Capacity of a Tumor
This factor refers to the rate at which the cancer cells divide to form more cells. Cells that have a high proliferative capacity divide more often and are more aggressive (fast-growing) than those with a low proliferative capacity. Patients who have tumors with cells that have a low proliferative capacity (meaing they divide less often and grow more slowly) tend to have a better prognosis.
Scientists estimate the proliferative capacity of the tumor using such tests as flow cytometry, which includes the S-phase fraction measurement. The S-phase fraction is the percentage of tumor cells that are dividing. Tumors with a high S-phase fraction tend to have an increased risk of recurrence.
The activation of an oncogene (a gene that causes or promotes unrestrained cell growth) can make normal cells become abnormal or convert a normal cell into a tumor cell. Patients whose tumor cells contain an oncogene called HER-2/neu, also called erb B-2, may be more likely to have a recurrence. Some research studies suggest that HER-2/neu may be associated with resistance to certain anticancer drugs; however, more research is needed.
Although prognostic factors provide important information about the risk of recurrence, they do not enable doctors to predict exactly who will be cured by primary therapy and who may benefit from adjuvant therapy. Decisions about adjuvant therapy for breast cancer must be made on an individual basis, taking into account the prognostic factors described previously, the woman's menopausal status (whether she has gone through menopause), her general health, and her personal preference. This complicated decision-making process is best carried out by consulting an oncologist, a doctor who specializes in cancer treatment.