Breast Tumor Recurrence: Radiation Plus Tamoxifen May Be Better Than Either Treatment Alone
Key Words breast cancer, recurrence, radiation therapy, tamoxifen. (Definitions of many terms related to cancer can be found in the Cancer.gov Dictionary.)
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.
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