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This report is from AHRQ's Data Points Publication Series.
Women with ductal carcinoma in situ (DCIS) were more likely to be treated with tamoxifen than an aromatase inhibitor (AI). For women with early invasive breast cancer, the reverse pattern was seen, with AI use more common than tamoxifen use.
Use of endocrine therapy declined in the five years following diagnosis for both DCIS and early invasive breast cancer. At all time points, use was higher for early invasive breast cancer, but declines were also greater.
Endocrine therapy use was associated with similar demographic characteristics for DCIS and early invasive breast cancer. In both groups, use declined with age.
Tumor characteristics were more strongly related to therapy use for women with early invasive disease than DCIS. With early invasive disease, use increased with increasing tumor size and declined with higher grade. For DCIS, patterns across both factors were less clear.
Endocrine therapy use was highest for women with DCIS treated with breast-conserving surgery plus radiation therapy (BCS+RT) compared with either mastectomy or BCS alone. For women with early invasive cancers, therapy was highest for women treated with BCS+RT and lowest for women treated with BCS alone.
In 2012, approximately 230,000 women in the United States were diagnosed with invasive breast cancer. In addition, about 60,000 women were diagnosed with ductal carcinoma in situ (DCIS), a possible risk factor for invasive breast cancer. Most breast cancers (about 75%) contain significant numbers of estrogen receptors (this is called estrogen receptor positive or ER+). In these cases, tumor growth is stimulated by the presence of estrogen.
Two types of endocrine medications treat ER+ DCIS and early invasive breast cancer: tamoxifen and aromatase inhibitors (AIs). Both act by reducing the amount of estrogen that reaches the tumor. Tamoxifen is a selective ER modulator that prevents estrogen from binding to the receptors. In contrast, AIs block the synthesis of estrogens. Currently, three AIs are on the market: anastrozole, letrozole, and exemestane. Both tamoxifen and AIs have been shown in randomized trials to reduce the risk of breast cancer recurrence and the development of a new primary tumor in the contralateral (opposite) breast.
Treatment of DCIS and early invasive breast cancer, regardless of ER status, includes mastectomy or breast-conserving surgery (BCS) (recommended in conjunction with radiation therapy [RT] or mastectomy). In addition, guidelines from the National Comprehensive Cancer Network (NCCN) recommend endocrine treatment with tamoxifen or AIs for at least five years for women with ER+ invasive breast cancer. Current NCCN guidelines recommend that physicians consider tamoxifen treatment for five years for patients with DCIS, especially those with ER+ disease; however, NCCN guidelines do not specifically recommend treatment with AIs.
Studies of adherence to AIs and tamoxifen find that up to one-third of women discontinue use within three years of starting. Adverse effects are the most common reason for discontinuation. Tamoxifen use is associated with more hot flashes and with gynecologic problems such as uterine cancer.
AI use is associated with increased cardiovascular disease, bone loss, and painful joints. Both drugs seem to have similar adherence problems despite distinct adverse effect profiles. Prior to the passage of the Medicare Part D benefit, the Medicare program provided no coverage for tamoxifen or AIs; however, both classes of medication are now included in Part D benefits. Thus, beginning in 2007, it is possible to examine use of these medications among elderly patients enrolled in Medicare Part D.
In this report, we sought to quantify the use of tamoxifen and AIs in 2007 and 2008 among older women within five years of diagnosis with DCIS or early invasive breast cancer (i.e., those diagnosed between 2002 and 2007.
Endocrine therapies have become an important strategy for preventing new primary breast cancers and invasive recurrences for women diagnosed with DCIS or early invasive breast cancer. Our study found that the endocrine therapy of choice varied strongly by stage at diagnosis and that use of therapy varied by patient tumor and demographic characteristics. It appears that while rates of use are higher for women with early invasive cancers than for DCIS, the decline in use over the five years postdiagnosis is also greater.
Further work is needed to understand the patient and provider factors associated with these patterns and to develop strategies promoting the most appropriate use of endocrine therapies for women diagnosed with breast cancer.