Breast cancer--influence of growth rate on prognosis and treatment evaluation: a study based on mastectomy scar recurrences.

The growth rate of a mammary cancer can be calculated when a recurrence appears in the mastectomy scar. Growth rate can, at times, be approximated from the patient's history with reasonable accuracy. Approximately half of breast cancers exhibit rapid growth (tumor doubling time (Td), up to 25 days); one-third grow at an intermediate rate (Td 26 to 75 days) and 15% grow slowly (Td 76 days or longer). Anatomic (TNM) staging does not define a homogeneous patient group in breast cancer. Within each stage, there are rapid, intermediate, and slow-growing tumors. The prognosis varies importantly with the growth rate characteristics of the tumor. Survival is the product of the tumor doubling time and the number of tumor doublings through which the patient lives. Slowly growing and intermediate growth rate tumors are associated with a high percentage of 5-year survivors after mastectomy (between 80 and 100%). Rapidly growing tumors have few 5-year survivors. When survival after mastectomy is measured in the number of tumor doublings, the differences in survival of the three groups tended to disappear, indicating that in this select group of patients with scar recurrence there was no therapeutic advantage in any of the three groups, despite the differences in the survival times. The appreciable number of patients with tumors exhibiting slow or intermediate growth rates, in any series, suggests that the use of the 5-year interval is an inadequate measure of therapeutic response in breast cancer and may actually be misleading.