Role of adjuvant endocrine therapy in early-stage breast cancer

The value of adjuvant endocrine therapy in saving lives of women with estrogen receptor-positive (ER(+)) early-stage breast cancer cannot be disputed. Tamoxifen has proven to be effective in improving relapse-free and overall survival in both pre- and postmenopausal women with ER(+) early-stage breast cancer. In the meta-analysis of the Early Breast Cancer Trialists' Collaborative Group, the proportional reduction in recurrence and mortality for 5 years of tamoxifen therapy was 50% and 28% respectively for patients with ER(+) tumors. These reductions in recurrence and mortality were similar in both lymph node-negative (N(-)) and lymph node-positive (N(+)) patients and translate to an absolute improvement in 10-year survival of approximately 11% in N(+) patients and 6% in N(-) patients. Current data suggest that about 5 years of tamoxifen therapy is the optimal duration of treatment. For women with ER(-)/progesterone receptor-negative (PR(-)) tumors, tamoxifen does not lower the risk of distant metastases or improve survival. In ER(+) patients, the addition of tamoxifen to chemotherapy further lowers the risk of recurrence by about 30% to 40% when compared to chemotherapy alone. In premenopausal women with ER(+) breast cancer, ovarian ablation has proven to be as effective as chemotherapy in improving both relapse-free and overall survival and the potential additive role of ovarian ablation to chemotherapy and/or tamoxifen is presently being explored in clinical trials. The combination of tamoxifen and ovarian ablation is currently being tested and may be superior to tamoxifen alone. In addition, newer, more effective, and less toxic aromatase inhibitors are also being evaluated in clinical trials in the adjuvant setting and have great promise. "Pure" antiestrogens or selective estrogen receptor down-regulators (SERDs) will be studied in adjuvant clinical trials in the near future. Recent data also suggest that molecular markers such as HER-2/neu may predict the response to endocrine therapy, and other predictive factors are currently being evaluated. Lastly, there is renewed interest in neoadjuvant endocrine therapy, a treatment option that may select those patients with early-stage breast cancer most likely to benefit from endocrine therapy.     

Development and clinical utility of a 21-gene recurrence score prognostic assay in patients with early breast cancer treated with tamoxifen

Although patients diagnosed with axillary node-negative estrogen receptor-positive breast cancer have an excellent prognosis, about 15% of them fail after 5 years of tamoxifen treatment. Clinical trials have provided evidence that there is a significant benefit from chemotherapy for these patients, but it would be significant overtreatment if all of them were treated with chemotherapy. Therefore, context-specific prognostic assays that can identify those who need chemotherapy in addition to tamoxifen, or those who are essentially cured by tamoxifen alone, and can be performed using routinely processed tumor biopsy tissue would be clinically useful. Using a stepwise approach of going through independent model-building and validation sets, a 21-gene recurrence score (RS), based on monitoring of mRNA expression levels of 16 cancer-related genes in relation to five reference genes, has been developed. The RS identified approximately 50% of the patients who had excellent prognosis after tamoxifen alone. Subsequent study suggested that high-risk patients identified with the RS preferentially benefit from chemotherapy. Ideally the RS should be used as a continuous variable. A prospective study-the Trial Assigning Individualized Options for Treatment (Rx) (TAILORx)-to examine whether chemotherapy is required for the intermediate-risk group defined by the RS is accruing in North America.     

Findings from recent National Surgical Adjuvant Breast and Bowel Project adjuvant studies in stage I breast cancer.

Before 1989, credible information about the treatment of breast cancer was derived mainly from randomized clinical trials that enrolled women with either metastatic (stage IV); locally advanced (stage III); or primary, operable, axillary lymph node-positive (stage II) disease. This report provides information from six recent National Surgical Adjuvant Breast and Bowel Project (NSABP) trials involving lymph node-negative (stage I) patients. Findings from NSABP B-13 demonstrated, through 14 years of follow-up, improvements in disease-free survival (DFS) and overall survival from methotrexate and fluorouracil (MF), regardless of age, in women with estrogen receptor (ER)-negative tumors. Results from NSABP B-19, which was conducted with similar patients, demonstrated, through 8 years, a greater overall DFS and survival advantage with cyclophosphamide and MF (CMF) than that observed with MF. Findings from NSABP B-23, in which patients similar to those in B-13 and B-19 were randomly assigned to receive CMF plus placebo, CMF plus tamoxifen (TAM), doxorubicin (Adriamycin) and cyclophosphamide (AC) plus placebo, or AC plus TAM, demonstrated no difference in relapse-free survival (RFS) or overall survival among the four groups through 5 years, either for all patients or relative to age. NSABP B-14, which was carried out in women with ER-positive tumors, compared the outcomes of those who received either placebo or TAM. Through 14 years, superior DFS and overall survival advantages, as well as a reduction in contralateral breast cancer, were observed with TAM. No additional benefit resulted from TAM administration beyond 5 years. Findings from NSABP B-20, a second study conducted in patients with ER-positive tumors, showed, after 8 years, both a DFS and an overall survival advantage from TAM plus either MF or CMF over that achieved with TAM alone. A recent meta-analysis in women with negative lymph nodes and either ER-negative or ER-positive tumors of less than or equal to 1 cm in size was conducted using patients from five NSABP trials. After 8 years, the RFS in women with ER-negative tumors was greater in the group treated with surgery and chemotherapy than in those who underwent surgery alone. In women with ER-positive tumors, RFS and overall survival advantages were observed from the addition of chemotherapy to TAM when that treatment regimen was compared with TAM alone. In addition, evidence has been presented from NSABP B-21, a trial evaluating radiation therapy (XRT) and/or TAM for the prevention of ipsilateral breast tumor recurrence (IBTR) after lumpectomy in women with tumors less than or equal to 1 cm. Findings have shown that XRT is superior to TAM and that XRT + TAM is superior to XRT alone for preventing IBTR. The findings demonstrate that chemotherapy and/or hormonal therapy is effective for the management of women with negative axillary lymph nodes and either ER-negative or ER-positive tumors. Because it also has been proven effective in women with tumors less than or equal to 1 cm, such therapy might also be considered in the treatment of that patient population.     

Endocrine effects of adjuvant chemotherapy and long-term tamoxifen administration on node-positive patients with breast cancer

Ovarian and pituitary hormones were determined in pre- and postmenopausal breast cancer patients before and at intervals during adjuvant chemotherapy or chemotherapy plus tamoxifen (TAM). Chemotherapy did not affect gonadotrophin levels in postmenopausal patients; however, inclusion of TAM in the regimen produced a partial (approximately 50%) reduction in circulating levels of luteinizing hormone (LH) and follicle-stimulating hormone. Gonadotrophin levels remained reduced as long as TAM therapy continued, at which time they rose to postmenopausal values. Chemotherapy (6-12 months) caused ovarian failure in premenopausal patients with decreases in estrogen (estrone plus estradiol) and rises in gonadotrophin levels to postmenopausal levels. Inclusion of TAM in the regimen caused an initial 3-fold rise in peak circulating estrogen levels before ovarian failure (6-9 months of therapy). Some younger patients (approximately 40 years of age) who had a short course (4 months) of chemotherapy plus TAM followed by continuous TAM therapy alone resumed ovulatory menstrual cycles. Estrogen, progesterone, and follicle-stimulating hormone levels were increased compared with control subjects. Those patients who experienced ovarian failure with adjuvant chemotherapy plus TAM only had a partial rise in gonadotrophins compared with patients receiving chemotherapy alone. TAM maintained the levels of gonadotrophins for as long as therapy was administered, at which time they rose to postmenopausal levels. Although TAM exhibited estrogen-like effects on gonadotrophins there was no estrogen-like increase in circulating prolactin levels in either pre- or postmenopausal patients. One patient experienced an estrogen receptor-positive recurrence during long-term tamoxifen therapy. Serum levels of tamoxifen and metabolites declined in the year prior to the recurrence and this was associated with a rise in gonadotrophins. This indicated noncompliance by the patient. Compliance can be monitored either directly with serum levels of TAM or by serial gonadotrophin determinations. We suggest that the optimal antitumor activity of TAM will be achieved in a low estrogen environment with continuous high levels of the drug in the serum. We recommend that patients undergoing long-term TAM therapy be monitored for complete ovarian failure and drug compliance.     

Adjuvant therapy approaches to breast cancer: Should taxanes be incorporated?

The triplet of docetaxel, doxorubicin, and cyclophosphamide (TAC) has emerged as an alternative chemotherapy regimen for adjuvant management of node-positive breast cancer. Based on recently reported 3-year data from the Breast Cancer International Research Group (BCIRG) 001, disease-free survival was significantly higher in patients who underwent adjuvant chemotherapy with TAC rather than the established regimen of 5-fluorouracil, doxorubicin, and cyclophosphamide (FAC). TAC reduced the risk of disease recurrence in estrogen receptor-positive and -negative patients. Whereas overall survival was not significantly different between the two groups, TAC led to a significant reduction in mortality in the subset of patients with one to three involved axillary lymph nodes. Overall, these interim BCIRG 001 results, coupled with those from Cancer and Leukemia Group B-9344 and National Surgical Adjuvant Breast and Bowel Project (NSABP) B-28 (phase III trials of sequential adjuvant chemotherapy with doxorubicin and cyclophosphamide followed by paclitaxel), suggest that taxanes are a valuable component of adjuvant chemotherapy for patients with node-positive breast cancer, including those with estrogen receptor positivity and/or extensive lymph node involvement. Accumulating data in the neoadjuvant setting lend further support to the view that the taxanes confer clinically meaningful benefits in the management of early-stage breast cancer. Such ongoing studies as NSABP B-30 will be instrumental in establishing the relative merits of sequential versus concurrent taxane-anthracycline adjuvant regimens for patients with node-positive breast cancer.     

Assessing the cost effectiveness of adjuvant therapies in early breast cancer using a decision analysis model

Summary Background: We have developed a decision analysis model that uses the results of available randomized controlled trials to model the natural history of early breast cancer and assess the potential clinical and financial effects of using adjuvant therapies. Patients and Methods: The original model was used to assess the impact of chemotherapy in hypothetical groups of 45-year-old and 60-year-old node-negative, estrogen receptor-negative women. Using the 1992 Early Breast Cancer Trialists' Collaborative Group report, we have expanded and revised the model to assess: 1) the role of tamoxifen alone, chemotherapy alone, or combined therapy in pre-menopausal women, and 2) chemotherapy in elderly women with node-negative, estrogen receptor-negative cancer. Results: For pre-menopausal women, we found that chemotherapy increases quality adjusted life expectancy and survival by a substantial amount at a cost less than most accepted medical interventions. Combined therapy is beneficial and cost-effective in estrogen receptor-positive cancer. For the elderly, chemotherapy prolongs survival but to a lesser extent compared to younger women. The cost of this benefit is high but within the range of commonly reimbursed procedures for women under age 75 without other co-existing conditions. Conclusions: For most patients some form of adjuvant therapy is beneficial and cost-effective. The model builds upon the data derived from collaborative efforts assessing the effectiveness of adjuvant therapies. The model highlights the need for an equal commitment to assessing the economic and quality of life impacts of breast cancer treatments.This minisymposium was presented December 8, 1992, at the annual San Antonio Breast Cancer Symposium, and was sponsored by educational grants from Amgen and from Bristol-Myers Oncology Division.     

The ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial: an update

Until recently, tamoxifen was the only adjuvant endocrine therapy for postmenopausal women with hormone receptor-positive, early-stage breast cancer. However, the first efficacy update from the ATAC (Arimidex, Tamoxifen, Alone or in Combination) trial has introduced a choice of adjuvant therapy in this setting. After a median follow-up of 47 months, these data indicated that anastrozole continued to show superior efficacy compared with tamoxifen, including significantly greater disease-free survival, a longer median time to recurrence, and a reduced incidence of contralateral breast cancer. Anastrozole also exhibited a number of important tolerability benefits compared with tamoxifen, including reduced incidences of thromboembolic events, vaginal bleeding, and endometrial cancer. Additional ATAC subprotocols included the examination of bone mineral density and its associated sequelae, endometrial abnormalities, and quality of life. The results of these studies support the primary conclusions of the main efficacy and safety analyses: the efficacy benefits of anastrozole were not at the expense of quality of life, anastrozole was associated with reduced endometrial stimulation compared with tamoxifen, and only patients receiving tamoxifen had endometrial atypical hyperplasia. Anastrozole was associated with a modest loss of bone mineral density and an initial increase of fractures compared with tamoxifen. However, the fracture rate with anastrozole stabilizes after 2 years, and indirect comparison suggests that any increased fracture risk with anastrozole is modest. This review concludes that, based on the overall risk-benefit profile from the ATAC study, anastrozole is a rational alternative to tamoxifen for the adjuvant treatment of women with hormone-sensitive early-stage breast cancer.     

Emerging role of aromatase inhibitors in the adjuvant setting

Aromatase inhibitors (AIs) have been approved as second-line treatment for estrogen receptor-positive (ER+) metastatic breast cancer after first-line treatment with the selective estrogen receptor modulator (SERM) tamoxifen. Anastrozole and letrozole have also recently been widely approved as first-line endocrine therapy for postmenopausal women with hormone receptor-positive metastatic breast cancer. The three third-generation selective oral AIs approved for use in the United States include two nonsteroidal agents, anastrozole (Arimidex) and letrozole (Femara), and the irreversible steroidal inhibitor exemestane (Aromasin). Several major ongoing clinical trials with a variety of treatment regimens are comparing the relative efficacy of tamoxifen with the steroidal and nonsteroidal AIs in the adjuvant setting. The first strategy compares an AI against tamoxifen directly. Among these are the ATAC (Arimidex, Tamoxifen Alone or in Combination) trial (anastrozole), the BIG FEMTA (Femara-Tamoxifen Breast International Group) trial (letrozole), and the EXEM and TEAM (exemestane) trials. A second strategy is examining the use of an AI as an extension after the initial 5 years of tamoxifen. Examples of this trial design are the MA-17 (letrozole) and the National Surgical Adjuvant Breast and Bowel Project (NSABP B-33, exemestane) trials. A third approach is the use of these agents in sequence with tamoxifen as therapy within the initial 5 postoperative years. Examples of this approach are the International Collaboration Cancer Group trial (tamoxifen for 2-3 years followed by either tamoxifen or exemestane for the remainder of the 5-year period), the BIG FEMTA trial (patients are crossed over from tamoxifen to Ietrozole or letrozole to tamoxifen), and the Arimidex-Nolvadex (ARNO) trial (patients receiving tamoxifen are randomized either to continue with tamoxifen or to switch to anastrozole). A single trial is comparing tamoxifen and anastrozole as initial 5-year therapy, or a combination of the two. The study addressing this design is the ATAC trial. Finally, a small trial in Norway is comparing 2 years of an AI versus a placebo in very low-risk patients with receptor-positive breast tumors. Most adjuvant trials have companion studies associated with the main protocol. These are to determine the end-organ effects of the inhibitors and include measurements of quality of life, bone and lipid metabolism, and endometrial effects. This review addresses the clinical implications of these studies of AIs.     

Cost-utility of the 21-gene recurrence score assay in node-negative and node-positive breast cancer

The 21-gene recurrence score (Oncotype DX: RS) appears to augment clinico-pathologic prognostication and is predictive of adjuvant chemotherapy benefit in node-negative (N-) and node-positive (N+), endocrine-sensitive breast cancer. RS is a costly assay that is associated with good 'value for money' in N- disease, while economic evaluations in N+ disease based on most recent data have not been conducted. We examined the cost-utility (CU) of a RS-guided adjuvant strategy, compared to current practice without RS in N- and N+, endocrine-sensitive, breast cancer from a Canadian health care system perspective. A generic state-transition model was developed to compute cumulative costs and quality-adjusted life years (QALYs) over a 25-year horizon. Patient outcomes with and without chemotherapy in RS-untested cohorts and in those with low, intermediate and high RS were examined based on the reported prognostic and predictive impact of RS in N- and N+ disease. Chemotherapy utilization (current vs. RS-guided), unit costs and utilities were derived from a Nova Scotia Canadian population-based cohort, local unit costs and the literature. Costs and outcomes were discounted at 3% annually, and costs were reported in 2011 Canadian dollars ($). Probabilistic and one-way sensitivity analyses were conducted for key model parameters. Compared to a non-RS-guided strategy, RS-guided adjuvant therapy was associated with $2,585 and $864 incremental costs, 0.27 and 0.06 QALY gains, and resultant CUs of $9,591 and $14,844 per QALY gained for N- and N+ disease, respectively. CU estimates were robust to key model parameters, and were most sensitive to chemo utilization proportions. RS-guided adjuvant therapy appears to be a cost-effective strategy in both N- and N+, endocrine-sensitive breast cancer with resultant CU ratios well below commonly quoted thresholds.     

Systemic therapy in node-negative patients: updated findings from NSABP clinical trials. National Surgical Adjuvant Breast and Bowel Project.

This report updates findings from two National Surgical Adjuvant Breast and Bowel Project (NSABP) clinical trials conducted to evaluate the worth of systemic therapy for the treatment of node-negative breast cancer patients. In trial B-13, 737 women with estrogen receptor (ER)-negative tumors treated by sequential methotrexate and fluorouracil (MTX----5-FU) followed by leucovorin were compared with a control group treated by surgery alone. Findings for all patients through 5 years of follow-up indicate a 27% reduction in treatment failure as a result of MTX----5-FU (76% vs 67%). While patients 49 years old or less and 50 years old or more benefited significantly from MTX----5-FU, the effect on disease-free survival (DFS) was greatest in those 50 years or older, where a 50% reduction in treatment failure occurred (86% vs 72%). A 69% reduction in mortality resulting from MTX----5-FU was observed in the older group (95% vs 84%). Trial B-14 compared placebo with tamoxifen (TMX) in 2844 patients with ER-positive tumors. As originally reported, findings through 5 years of follow-up indicate a significant reduction (36%) in treatment failure as a result of the TMX (82% vs 72%). Improvement in DFS was highly significant in both age groups. In patients 49 years old or younger, there was a 44% reduction in DFS (81% vs 66%) and, in those 50 years old or more, a 31% reduction (82% vs 74%). A Cox proportional hazards model failed to indicate a benefit from MTX----5-FU and TMX in all patient subgroups. Both therapies reduced local-regional and distant recurrence, as well as breast tumor recurrence following lumpectomy. Updated findings from trials B-13 and B-14 continue to support our conclusions that (a) no subgroups of node-negative patients that we examined have such a good outcome as to preclude the use of effective systemic therapy in their treatment and (b) despite the benefits observed from MTX----5-FU and TMX, no subgroup of patients was so affected as to preclude use of a particular subgroup in assessing other therapy regimens in additional clinical trials. The identification and evaluation of markers to determine which patients should receive systemic therapy are of the highest priority. At present, however, the use of markers for therapeutic decision making regarding individual patients is tenuous.     

Results of two randomized trials evaluating adjuvant anthracycline-based chemotherapy in 1146 patients with early breast cancer

Two randomized trials evaluated the effect of 6 courses of anthracycline-based chemotherapy in early breast cancer. A total of 1 146 patients were included: 311 high-risk node-negative premenopausal patients and 835 high-risk node-negative or node-positive postmenopausal patients. Patients were randomized after surgery to receive either no chemotherapy (control group) or 6 courses of anthracycline-based chemotherapy (CT group). Postmenopausal patients received adjuvant tamoxifen for at least two years. Radiotherapy was delivered after completion of chemotherapy in the CT group. The 10-year disease-free survival (DFS) rates were 60% in the control group and 65% in the CT group (log-rank test, p = 0.01). The 10-year distant metastasis rates were 28% and 23% (p = 0.02), and the 10-year local recurrence rates were 12% and 10%, respectively (p = 0.24). Chemotherapy was significantly less effective in post-menopausal patients with estrogen receptor-positive tumors. Adjuvant anthracyclin-based chemotherapy yielded a significant benefit for DFS by lowering the risk of distant metastases. After up to 10 years of follow-up, deferring radiotherapy after chemotherapy did not compromise local control.     

Impact of systemic treatment on local control for patients with lymph node-negative breast cancer treated with breast-conservation therapy.

PURPOSE: To determine the impact of tamoxifen and chemotherapy on local control for breast cancer patients treated with breast-conservation therapy. PATIENTS AND METHODS: The data from 484 breast cancer patients who were treated with breast-conserving surgery and radiation were analyzed. Only patients with lymph node-negative disease were studied to provide comparative groups with a similar stage of disease and a similar competing risk for distant metastases. Actuarial local control rates of the 277 patients treated with systemic therapy (128, chemotherapy with or without tamoxifen; 149, tamoxifen alone) were compared with the rates for the 207 patients who received no systemic treatment. Only 10% of the patients had positive (2%), close (3%), or unknown margin status (5%). RESULTS: Patients treated with systemic therapy had improved 5-year (97.5% v 89.8%) and 8-year (95.6% v 85.2%) local control rates compared with those that did not receive systemic treatment (P =.004, log-rank test). There was no statistical difference in local control between patients treated with chemotherapy and patients treated with tamoxifen alone (P =.219). Systemic treatment, margin status, young patient age, estrogen and progesterone receptor status, and primary tumor size were analyzed in a Cox regression analysis. The use of systemic treatment was the most powerful predictor of local control: patients who did not receive systemic treatment had a relative risk of local recurrence of 3.3 (95% confidence interval, 1.5 to 7.5; P =.004). CONCLUSION: In this retrospective analysis, systemic therapy appears to contribute to long-term local control in patients with lymph node-negative breast cancer treated with breast-conservation therapy.     

DNA-methylation of the homeodomain transcription factor PITX2 reliably predicts risk of distant disease recurrence in tamoxifen-treated, node-negative breast cancer patients--Technical and clinical validation in a multi-centre setting in collaboration with the European Organisation for Research and Treatment of Cancer (EORTC) PathoBiology group

Our aim was to identify and validate DNA-methylation markers associated with very good outcome in node negative, hormone receptor positive breast cancer patients after adjuvant endocrine therapy which might allow identifying patients who could be spared the burden of adjuvant chemotherapy. Using a methylation microarray, we analysed 117 candidate genes in hormone receptor-positive tumours from 109 breast cancer patients treated by adjuvant tamoxifen. Results were validated in an independent cohort (n=236, 5 centres). Independent methodological validation was achieved by a real-time polymerase chain reaction (PCR)-based technique. DNA methylation of PITX2 showed the strongest correlation with distant recurrence. Its impact on patient outcome was validated in the independent cohort: 86% of patients with low PITX2 methylation were metastasis-free after 10 years, compared to 69% with elevated PITX2 methylation. Moreover, PITX2 methylation added significant independent information to established clinical factors. All clinical and technical findings were confirmed by quantitative DNA-methylation PCR. These results provide strong evidence that DNA-methylation analysis allows clinically relevant risk assessment in tamoxifen-treated primary breast cancer. Based on PITX2 methylation, about half of hormone receptor-positive, node-negative breast cancer patients receiving adjuvant tamoxifen monotherapy can be considered low-risk regarding development of distant recurrences and may thus be spared adjuvant chemotherapy. In addition, these low-risk postmenopausal patients seem to respond sufficiently well to tamoxifen so that they may not require up-front aromatase inhibitor therapy.     

Combination of anthracyclines and anti-CD47 therapy inhibit invasive breast cancer growth while preventing cardiac toxicity by regulation of autophagy

Background

The 21-gene recurrence score (RS) predicts outcome and benefit from adjuvant chemotherapy benefit in breast cancer patients treated with adjuvant endocrine therapy. In the NSABP B-28 study, we evaluated the 21-gene RS for its prognostic impact and its ability to predict benefit from paclitaxel (P) in node-positive, estrogen receptor-positive (ER+) breast cancer patients treated with adjuvant chemotherapy plus tamoxifen.

Methods

The B-28 trial compared doxorubicin/cyclophosphamide (AC) with AC followed by P in 3060 patients. Tamoxifen for 5 years was also given to patients > 50 years and those < 50 years with ER+ and/or progesterone receptor-positive (PR+) tumors. The present study includes 1065 ER-positive, tamoxifen-treated patients with RS assessment. Median follow-up time was 11.2 years.

Results

In univariate analyses, RS was a significant predictor of outcome. In multivariate analyses, RS remained a significant independent predictor of outcome beyond clinico-pathologic factors, age, and type of surgery (p < 0.001). In the study population (n = 1065), the disease-free survival (DFS) hazard ratio (HR) with adding P to AC was 0.87 (95% CI 0.72–1.05; p = 0.14). RS was not a significant predictor of P benefit: for DFS, HRs for adding P to AC in RS low, intermediate, and high subgroups were 1.01 (95% CI 0.69–1.47; p = 0.99), 0.84 (95% CI 0.62–1.14; p = 0.26), and 0.81 (95% CI 0.60–1.10; p = 0.21), respectively (interaction p = 0.64). Similar findings were observed for the other study endpoints.

Conclusions

RS maintains significant prognostic impact in ER-positive, node-positive patients treated with adjuvant chemotherapy plus tamoxifen. However, RS did not significantly predict benefit from adding paclitaxel to AC chemotherapy. (Trial Registration: PDQ: NSABP-B-28).

     

Antiaromatase agents after adjuvant tamoxifen: rationale and clinical implications

Although tamoxifen is considered standard adjuvant hormonal therapy in receptor-positive, stage I and II breast cancer, information on its optimal duration of administration has only been reported recently and, for many, the subject is still a matter of scientific debate. Data suggest that there is a time period beyond which, if tamoxifen is continued, it may become ineffective or even detrimental to the patient. Tamoxifen is usually discontinued after approximately 5 years of therapy, at which time most patients are thought to be disease free; however, some patients may harbor residual micrometastases. A fraction of these patients will have micrometastatic tumor cells that are still responsive to tamoxifen, and tamoxifen discontinuation could result in cancer cell growth. The preponderance of clinical data, however, indicate that a greater fraction of patients will have micrometastatic tumor cells that have become progressively resistant to tamoxifen. In fact, tumor cell growth could be stimulated by continued therapy with the drug. Although in some patients the micrometastatic tumor cells may have become hormonally unresponsive, in most cases (tamoxifen-responsive or tamoxifen-stimulated micrometastases), the tumor remains hormonally responsive. Therefore, the use of anti-aromatase agents to reduce the level of estrogenic stimulation and, as a result, the risk of recurrence may prove to be a valuable approach at the time of tamoxifen discontinuation. The National Surgical Adjuvant Breast and Bowel Project (NSABP) is in the final stages of developing a clinical trial (NSABP B-33) to evaluate the effect of administering 2 years of therapy with the aromatase inactivator exemestane to postmenopausal, receptor-positive patients who have completed 5 years of tamoxifen therapy and are disease free at the time of tamoxifen discontinuation.     

Who should not receive chemotherapy? Data from American databases and trials.

The demonstration of the effectiveness of chemotherapy in both premenopausal and postmenopausal women, regardless of estrogen receptor (ER) status, raises the question of whether all breast cancer patients should receive chemotherapy. Several patient groups with such a favorable long-term prognosis that they will obtain an extremely small benefit from chemotherapy can be identified. They include patients with lymph node-negative tumors of 1 cm or less in size, those with grade 1 tumors between 1.1 and 2.0 cm in size, and those with tumors of favorable histologic type (tubular and mucinous) up to 3 cm in size. A patient subgroup in which it is not clear that the benefits of chemotherapy routinely exceed the risks is postmenopausal women with ER-positive, lymph node-negative cancers receiving tamoxifen. There is a wide variation in prognosis in this group, and chemotherapy should be reserved for those at high risk of recurrence. Finally, no benefit for chemotherapy in women aged 70 years and older has been identified. The high rate of death from causes other than breast cancer may negate small survival benefits, and after adjustment for quality of life, the duration of treatment exceeds the gain in life expectancy.     

Adjuvant chemotherapy with doxorubicin and cyclophosphamide in women with rapidly proliferating node-negative breast cancer

This prospective clinical trial was designed to assess the impact of adjuvant chemotherapy in women with rapidly proliferating node-negative breast cancer. This group has been predicted to have a 5-year disease-free survival (DFS) of 70% without adjuvant chemotherapy. In this study, 449 women with rapidly proliferating breast cancer (91% measured by S-phase fraction and 9% by histochemistry) received adjuvant chemotherapy with doxorubicin/cyclophosphamide (AC) plus tamoxifen for estrogen receptor-positive or progesterone receptor-positive cancer. The 5-year DFS was 90% (+/- 2%) and the 5-year overall survival was 94% (+/- 1%). At a median follow-up of 62 months, the strategy of administering 6 cycles of AC to women with T2 N0 cancer and 3 cycles in those with smaller T1 N0 cancers appeared to eliminate tumor size as a potential prognostic factor. Adjuvant chemotherapy with AC appears effective in reducing recurrence rates for women with rapidly proliferating node-negative breast cancer.     

Controversies in adjuvant endocrine treatment of premenopausal women

For patients with hormone receptor-positive breast cancer, some form of endocrine therapy is central to the management of their disease. For premenopausal patients in whom estrogen synthesis occurs primarily in the ovaries, current treatment options include ovarian ablation or suppression and selective estrogen receptor modulators such as tamoxifen and toremifene. Ovarian ablation and tamoxifen have demonstrated their effectiveness in the adjuvant setting, reducing the risk of recurrence and death. However, although some studies suggest ovarian ablation results in an equivalent outcome to chemotherapy alone, studies examining the combination have not demonstrated a clear benefit with the addition of ovarian suppression to standard chemotherapy. Results from trials combining ovarian suppression with tamoxifen have also been inconclusive. Finally, although aromatase inhibitors cannot be used as monotherapy in premenopausal patients, the reduction in the risk of recurrence observed with the integration of these agents into adjuvant regimens in postmenopausal patients when compared with the standard 5 years of tamoxifen has stimulated interest in evaluating the combination of ovarian suppression with an aromatase inhibitor in premenopausal women. Several ongoing trials will investigate these combinations as well as ovarian suppression plus tamoxifen.     

Optimizing adjuvant endocrine therapy in postmenopausal women with early-stage breast cancer: a decision analysis.

PURPOSE: The optimal adjuvant endocrine strategy for postmenopausal breast cancer is unknown. Options include the antiestrogen tamoxifen, estrogen deprivation with aromatase inhibitors, and sequential therapy with tamoxifen and then an aromatase inhibitor. METHODS: We developed Markov models to simulate 10-year disease-free survival among postmenopausal women with hormone receptor-positive breast cancer. The treatment strategies analyzed were 5 years of tamoxifen alone, 5 years of an aromatase inhibitor alone, and sequential treatment consisting of tamoxifen with cross over to an aromatase inhibitor at 2.5 or 5 years. Risk estimates were derived from reported randomized clinical trials. RESULTS: Sequential therapy with tamoxifen followed by cross over to an aromatase inhibitor at 2.5 years yielded a modest improvement in disease-free survival compared with planned aromatase inhibitor monotherapy. At 10 years, the cross-over strategy yielded absolute disease-free survival rates of 83.7% and 67.6% for node-negative and node-positive patients, respectively, compared with 82.6% and 65.5%, respectively, for aromatase inhibitor monotherapy, which is a 6% relative risk reduction. Sequential therapy improved disease-free survival estimates by year 6 after treatment initiation. Later cross over from tamoxifen to an aromatase inhibitor at 5 years did not further improve 10-year disease-free survival estimates. Sensitivity analyses suggest that sequential treatment strategies optimized 10-year disease-free and distant disease-free survival independent of the degree of the beneficial carryover effect after aromatase inhibitor therapy or the ratio of local to distant tumor recurrence. CONCLUSION: Modeling estimates suggest that sequential adjuvant therapy with tamoxifen followed by an aromatase inhibitor after 2.5 years yields improved outcomes compared with either drug alone or cross-over treatment after 5 years of tamoxifen.     

Partial breast irradiation versus whole breast radiotherapy for early-stage breast cancer: a decision analysis

PURPOSE: To compare the quality-adjusted life expectancy between women treated with partial breast irradiation (PBI) vs. whole breast radiotherapy (WBRT) for estrogen receptor-positive early-stage breast cancer. METHODS AND MATERIALS: We developed a Markov model to describe health states in the 15 years after radiotherapy for estrogen receptor-positive early-stage breast cancer. Breast cancer recurrences were separated into local recurrences and elsewhere failures. Ipsilateral breast tumor recurrence (IBTR) risk was extracted from the Oxford overview, and rates and utilities were adapted from the literature. We studied two cohorts of women (aged 40 and 55 years), both of whom received adjuvant tamoxifen. RESULTS: Assuming a no evidence of disease (NED)-PBI utility of 0.93, quality-adjusted life expectancy after PBI (and WBRT) was 12.61 (12.57) and 12.10 (12.06) years for 40-year-old and 55-year-old women, respectively. The NED-PBI utility thresholds for preferring PBI over WBRT were 0.923 and 0.921 for 40-year-old and 55-year-old women, respectively, both slightly greater than the NED-WBRT utility. Outcomes were sensitive to the utility of NED-PBI, the PBI hazard ratio for local recurrence, the baseline IBTR risk, and the percentage of IBTRs that were local. Overall the degree of superiority of PBI over WBRT was greater for 55-year-old women than for 40-year-old women. CONCLUSIONS: For most utility values of the NED-PBI health state, PBI was the preferred treatment modality. This result was highly sensitive to patient preferences and was also dependent on patient age, PBI efficacy, IBTR risk, and the fraction of IBTRs that were local.