TUMOR RECURRENCE AND TAMOXIFEN RESISTANCE: HOW IS RECURRENT BREAST CANCER TREATED?
For breast cancer that has recurred within the initially treated breast, an aggressive type of surgery is usually performed. If the earlier surgery was a lumpectomy or partial mastectomy, a complete mastectomy may now be required. Once the tumor and surrounding tissues have been removed, the tumor will be evaluated for the presence of estrogen and progesterone receptors. The decision to use chemotherapy, radiation, or hormone therapy will be based on the size and location of the tumor, nodal involvement, the presence or absence of receptors, and the prior use of chemotherapy drugs. For tumors considered to place the patient at high risk of recurrence, or when conservative surgery is performed, radiation is used subsequently to decrease the risk of another recurrence. As discussed earlier, for patients who have estrogen or progesterone receptors in their primary breast tumors, tamoxifen or another hormonal agent may be prescribed to control or prevent further tumor recurrence. Chemotherapy is also considered, depending on the kind of chemotherapy the patient received initially and how well she responded at that time.If the breast cancer has spread to a single site outside the breast, treatment depends largely on where the tumor is located. If the recurrence is in an area that is surgically operable and the tumor impairs the patient’s normal functioning, then the tumor may be surgically removed. For tumors of the bone or other tumors that are not readily operable, radiation may be used to reduce tumor size and alleviate symptoms.Chemotherapy is typically given to patients with rapidly progressing or receptor-negative breast cancer that has spread beyond the breast. At one time it was believed that patients with disseminated breast cancer had little chance of long-term response to chemotherapy. Drugs were given primarily to moderate the symptoms of the disease. Today we know that by using different chemotherapeutic combinations an improved quality of life can be achieved in at least 60 percent of these patients.Most beginning drug therapies will include either methotrexate or adriamycin. Once a patient no longer benefits from the first protocol, she may be given a different course of drugs. Typically, a patient responds to the initial course for 6 to 12 months. When she stops reacting to any of the conventional drug combinations, the patient may elect to take a new and untested drug or combination of drugs that seems promising. Some of these agents have had encouraging results in patients with advanced breast cancer.A patient with estrogen-receptor-positive breast cancer that has metastasized may be offered tamoxifen therapy before chemotherapy. Response to tamoxifen in patients with bone or soft-tissue metastasis is very good, and remission can last more than 12 months. Unfortunately, while response to tamoxifen may be as high as 75 percent in some groups, virtually all patients will eventually develop tamoxifen resistance and no longer respond. Once tamoxifen therapy fails to be effective, other hormonal agents such as aminoglutethimide, halotestin, megestrol, and leuprolide are available. As with tamoxifen, patients may initially respond satisfactorily, but eventually they develop resistance to all endocrine agents as well.*38\320\2*