Related Pages Breast Cancer Home Page 1 NCI's gateway for information about breast cancer. Highlights from ASCO 2000 2 A roundup of news highlights from the 2000 annual meeting of the American Society of Clinical Oncology.

Key Words breast cancer, recurrence, radiation therapy, tamoxifen. (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary ³.)

Women with very small breast tumors who received both radiation therapy and the drug tamoxifen after surgery had fewer recurrences of cancer in the same breast than women who received either radiation therapy or tamoxifen but not both, researchers report in the October 15, 2002, issue of the Journal of Clinical Oncology (see the journal abstract of the study).

The findings were originally presented by Norman Wolmark, M.D., of the National Surgical Breast and Bowel Project in May 2000 at the annual meeting of the American Society of Clinical Oncology.

The multicenter study involved 1,009 women who were randomly assigned to receive both radiation therapy and tamoxifen, radiation therapy plus a placebo, or tamoxifen alone after breast-conserving surgery. Most of the women were aged 50 or older and all had breast cancers of no more than 1 centimeter (less than a half-inch) in diameter.

After eight years of follow-up, 2.8 percent of the women who received both radiation therapy and tamoxifen had a recurrence of cancer in the same breast, compared with 9.3 percent of women who received radiation therapy plus a placebo and 16.5 percent of women who received tamoxifen alone.

Though everyone’s tumors were less than 1 centimeter, women with the smallest tumors (5 millimeters or less in diameter, less than a quarter-inch) were somewhat more likely to have a recurrence than women whose tumors were larger. This finding suggests that factors other than tumor size -- such as the tumor type, whether or not the tumor is sensitive to the hormones estrogen and progesterone, and the woman’s general health -- need to be considered when making treatment decisions, say the study authors, who were led by Bernard Fisher, M.D., of the University of Pittsburgh.

Choosing the best option for additional treatment after lumpectomy of very small breast tumors is difficult, Fisher and his colleagues add, because doctors currently have no reliable way of identifying which women are at higher risk for a recurrence of cancer.

The results of this study offer support for treating most women who have very small breast cancers with radiation therapy following conservative surgery, says Jeff Abrams, M.D., of the National Cancer Institute’s (NCI’s) Cancer Therapy Evaluation Program. In addition, he says, those whose tumors have receptors sensitive to estrogen would benefit from the inclusion of tamoxifen.

Addition of radiation therapy saves a significant number of women from eventually having to undergo mastectomy, even in this subgroup of women with very small tumors. “The effect of tamoxifen on recurrence is somewhat smaller, so side-effects of the drug must be considered when deciding to add it to radiation,” says Abrams.

However, other studies have shown that tamoxifen also has the benefit of preventing the spread of cancer outside the breast in women with tumors larger than 1 centimeter and of preventing the occurrence of new breast tumors. While no decrease in the spread of cancer outside the breast was proven in this study (probably due to the low risk of recurrences outside the breast in these women), tamoxifen did lower the risk of getting a tumor in the opposite breast, notes Abrams.

When considering the use of tamoxifen for women at low risk of recurrence, several rare but serious side-effects of tamoxifen need to be considered, says Abrams. These include an increased risk of uterine cancer, blood clots in the lung, and possibly stroke. “However, these side-effects are usually more than counterbalanced by the benefits of tamoxifen in women with invasive breast cancer.”

In about seven out of 10 cases of breast cancer, the cancer cells have areas on their surface called receptors to which hormones such as estrogen and progesterone attach, providing fuel for the cells’ growth into a tumor. Tamoxifen works by disrupting estrogen’s ability to help cancer cells grow. However, the drug is ineffective in breast cancers that are not fueled by estrogen. New studies are testing whether other anti-estrogen drugs are as effective as tamoxifen with fewer side-effects.

The current study was conducted by the National Surgical Adjuvant Breast and Bowel Project (NSABP), a large NCI-supported cancer clinical trials group, which has conducted many important trials that have produced advances in the treatment and prevention of breast cancer.

Glossary Terms

An operation to remove the breast cancer but not the breast itself. Types of breast-conserving surgery include lumpectomy (removal of the lump), quadrantectomy (removal of one quarter, or quadrant, of the breast), and segmental mastectomy (removal of the cancer as well as some of the breast tissue around the tumor and the lining over the chest muscles below the tumor). Also called breast-sparing surgery.

A type of hormone made by the body that helps develop and maintain female sex characteristics and the growth of long bones. Estrogens can also be made in the laboratory. They may be used as a type of birth control and to treat symptoms of menopause, menstrual disorders, osteoporosis, and other conditions.

Surgery to remove abnormal tissue or cancer from the breast and a small amount of normal tissue around it. It is a type of breast-sparing surgery.

Surgery to remove the breast (or as much of the breast tissue as possible).

An inactive substance or treatment that looks the same as, and is given the same way as, an active drug or treatment being tested. The effects of the active drug or treatment are compared to the effects of the placebo.

A type of hormone made by the body that plays a role in the menstrual cycle and pregnancy. Progesterone can also be made in the laboratory. It may be used as a type of birth control and to treat menstrual disorders, infertility, symptoms of menopause, and other conditions.

The use of high-energy radiation from x-rays, gamma rays, neutrons, protons, and other sources to kill cancer cells and shrink tumors. Radiation may come from a machine outside the body (external-beam radiation therapy), or it may come from radioactive material placed in the body near cancer cells (internal radiation therapy). Systemic radiation therapy uses a radioactive substance, such as a radiolabeled monoclonal antibody, that travels in the blood to tissues throughout the body. Also called irradiation and radiotherapy.

A study in which the participants are assigned by chance to separate groups that compare different treatments; neither the researchers nor the participants can choose which group. Using chance to assign people to groups means that the groups will be similar and that the treatments they receive can be compared objectively. At the time of the trial, it is not known which treatment is best. It is the patient's choice to be in a randomized trial.

A molecule inside or on the surface of a cell that binds to a specific substance and causes a specific physiologic effect in the cell.

A drug used to treat certain types of breast cancer in women and men. It is also used to prevent breast cancer in women who have had ductal carcinoma in situ (abnormal cells in the ducts of the breast) and in women who are at a high risk of developing breast cancer. Tamoxifen is also being studied in the treatment of other types of cancer. It blocks the effects of the hormone estrogen in the breast. Tamoxifen is a type of antiestrogen. Also called tamoxifen citrate.