A Method for Making Estimates of the Benefit of the Late Use of Letrozole in Patients Completing 5 Years of Tamoxifen

Extended adjuvant therapy with letrozole: reducing the risk of recurrence

Patients with all stages of primary breast cancer are at continuing risk of relapse following 5 years of adjuvant tamoxifen therapy, even in the absence of lymph node involvement. Tamoxifen has been the standard therapy for reducing risk of recurrence, although more than 50% of relapses and deaths occur after completion of tamoxifen. Tamoxifen use is associated with an increased risk of serious side effects, and extended use beyond 5 years may have a negative impact on disease-free survival. Extended adjuvant letrozole therapy confers a significant benefit in relapse-free survival. The approval of letrozole for this indication in the USA and in many European countries introduces a new, safe and effective treatment for disease-free patients seeking to reduce their long-term risk of recurrence.

Prediction model for estimating the survival benefit of adjuvant radiotherapy for gallbladder cancer

PURPOSE

The benefit of adjuvant radiotherapy (RT) for gallbladder cancer remains controversial because most published data are from small, single-institution studies. The purpose of this study was to construct a survival prediction model to enable individualized predictions of the net survival benefit of adjuvant RT for gallbladder cancer patients based on specific tumor and patient characteristics.

METHODS

A multivariate Cox proportional hazards model was constructed using data from 4,180 patients with resected gallbladder cancer diagnosed from 1988 to 2003 from the Surveillance, Epidemiology, and End Results database. Patient and tumor characteristics were included as covariates and assessed for association with overall survival (OS) with and without adjuvant RT. The model was internally validated for discrimination and calibration using bootstrap resampling.

RESULTS

On multivariate regression analysis, the model showed that age, sex, papillary histology, stage, and adjuvant RT were significant predictors of OS. The survival prediction model demonstrated good calibration and discrimination, with a bootstrap-corrected concordance index of 0.71. The model predicts that adjuvant RT provides a survival benefit in node-positive or >or= T2 disease. A nomogram and a browser-based software tool were built from the model that can calculate individualized estimates of predicted net survival gain attributable to adjuvant RT, given specific input parameters.

CONCLUSION

In the absence of large, prospective, randomized, clinical trial data, a regression model can be used to make individualized predictions of the expected survival improvement from the addition of adjuvant RT after gallbladder cancer resection.

A multidisciplinary approach to the management of breast cancer, part 2: therapeutic considerations

New approaches to breast cancer treatment have enhanced clinical outcomes and patient care. These approaches include advances in breast irradiation and hormonal and systemic adjuvant therapies. In addition to the identification of new drug targets and targeted therapeutics (eg, trastuzumab), there is renewed re-emphasis in the development of biomarkers for the prediction of response to therapy. One example is the pharmacogenetics of tamoxifen metabolism and the individualization of hormonal therapy. The current treatment of breast cancer continues to evolve rapidly, with new scientific and clinical achievements constantly changing the standard of care and leading to substantial reductions in breast cancer mortality. The goal of this article is to provide clinicians who care for women with breast cancer a multidisciplinary, state-of-the art approach to the treatment of these patients.

Continuing with letrozole offers greater benefits

OBJECTIVE

Tamoxifen has been at the foundation of adjuvant treatment to prevent disease recurrence in postmenopausal women with hormone-responsive early breast cancer. After 5 years of adjuvant tamoxifen therapy, however, options for further treatment are limited. Additional tamoxifen is not indicated, as no further benefit in disease-free survival (DFS) has been observed. The aromatase inhibitor letrozole significantly improves DFS over placebo in postmenopausal women who have completed 4.5-6.0 years of adjuvant tamoxifen.

MATERIALS AND METHODS

This article reviews the data supporting extended adjuvant letrozole therapy.

CONCLUSIONS

Extended adjuvant letrozole has been shown to be particularly effective in patients with node-positive disease, who are at a higher risk for disease recurrence, improving both DFS and overall survival. Extended adjuvant letrozole is associated with a significant increase in self-reported osteoporosis, but no significant increases in fracture, endometrial malignancies, hypercholesterolemia, or cardiovascular events and no worsening of quality of life, making it suitable for long-term use. The ASCO treatment guidelines recommend at least 2.5 years of extended adjuvant letrozole for patients completing tamoxifen therapy, based upon the MA.17 trial follow-up period. A recent cohort analysis now suggests that extended adjuvant letrozole treatment for at least 48 months is associated with greater benefit. The efficacy of letrozole for up to 10 years following tamoxifen is also being investigated.

Aromatase inhibitors in early breast cancer therapy: a variety of treatment strategies

Until recently, standard endocrine therapy for estrogen receptor-positive early breast cancer in the preoperative neoadjuvant and postoperative adjuvant settings was the selective estrogen receptor modulator tamoxifen. An alternate therapeutic approach is to suppress total-body estrogen synthesis using an aromatase inhibitor. The highly potent and specific third-generation aromatase inhibitors (anastrozole, exemestane and letrozole) have consistently demonstrated improved efficacy over tamoxifen in large randomised neoadjuvant and adjuvant clinical trials. As neoadjuvant therapy, compared with tamoxifen, all three aromatase inhibitors significantly improved breast-conserving surgery rates, but only letrozole achieved a significantly higher overall response rate. These agents have also been evaluated in three adjuvant strategies: instead of tamoxifen for 5 years, sequenced after 2-3 years of tamoxifen, or as extended adjuvant therapy following a full 5-year course of tamoxifen. In all cases, the aromatase inhibitor was significantly more effective in reducing the risk of recurrence, compared with tamoxifen in the first two approaches and with placebo or no treatment as extended therapy. Long-term aromatase inhibitor treatment is associated with less endometrial cancer, thromboembolic events and strokes than tamoxifen, but more musculoskeletal disorders and bone loss. Further investigation is focusing on identification of the patient subgroups most likely to benefit from each of these adjuvant therapy options.

Cost-Effectiveness of Letrozole in the Extended Adjuvant Treatment of Women with Early Breast Cancer

Adjuvant tamoxifen therapy for 5 years reduces recurrence in hormone receptor positive, post-menopausal women with early breast cancer, but offers no advantage when prolonged to another 5 years, during which the risk of recurrence remains high. Treating patients, who remain disease-free after 5 years of tamoxifen, with letrozole significantly reduces recurrence, regardless of nodal status. This study evaluated the life-time cost-utility of extended adjuvant letrozole therapy in 62-year-old patients from a third-party payer perspective. A Markov model incorporated locoregional, contralateral, and metastatic recurrences. The comparator was placebo. Event rates were based on published trials. Utility values were taken from a clinical trial and published literature. Costs were obtained from published literature, provincial payment schedules, cancer agencies, and drug plans formularies. Resource use reflected Canadian treatment patterns. Robustness of the model was tested using deterministic and probabilistic sensitivity analyses. Extended adjuvant letrozole therapy of a cohort consisting of 50% node-negative and 50% node-positive patients prolonged their lives on average by 0.466 years or 0.267 quality-adjusted life years (QALYs) at an additional cost of Can$8,031 per patient, yielding an incremental cost-utility ratio (ICUR) of $34,058 per QALY. Letrozole was more cost-effective in node-positive than in node-negative patients (Can$26,553 vs Can$46,049 per QALY). Results were robust to variations in age, healthcare costs, and utilities. The degree of confidence that the cost per QALY would be below Can$50,000 reached 100% for node-positive and 77% for node-negative patients. Extended adjuvant letrozole is cost-effective in both node-negative and node-positive patients having ICURs below Can$50,000/QALY.

Extended breast cancer treatment with an aromatase inhibitor (Letrozole) after tamoxifen: why, who and how long?

Breast cancer remains a leading cause of cancer death in women worldwide, and the risk for disease recurrence continues despite improvements in screening and treatment and the use of prophylactic estrogen-inhibiting therapies such as tamoxifen. A number of long-term studies now indicate a significant risk for breast cancer recurrence among patients who have undergone the currently recommended five years of tamoxifen adjuvant therapy following successful treatment of their initial disease. This ongoing recurrence risk extends even to patients commonly considered at low risk for relapse, that is, those with low-grade, small tumors, and/or node-negative disease. Treatment with tamoxifen for more than five years appears detrimental rather than beneficial and, therefore, tamoxifen is not indicated for use beyond the initial five years. Endometrial cancer and thromboembolism are among the serious adverse events that have been observed with long-term tamoxifen treatment. The aromatase inhibitors are able to reduce overall estrogen levels and appear to be better tolerated over a long term. Letrozole is the most potent aromatase inhibitor and has been available in Europe since 1996 and in the United States since 1997. Letrozole has been approved for first-line treatment of postmenopausal women with hormone-receptor-positive or hormone-receptor-unknown, advanced or metastatic breast cancer in the United States and Europe, as well as for neoadjuvant treatment (primary systemic therapy) of early breast cancer prior to surgery in many countries. The results of the pivotal MA-17 trial demonstrate that letrozole is unique in its ability to improve disease-free survival in breast cancer patients who have undergone tamoxifen therapy for five years. The MA-17 results indicate that extended adjuvant therapy with letrozole reduces risk of recurrence in this setting by 42%, reduces risk of distant recurrence (metastasis), and may improve patient survival in the node-positive patient population. The results also show letrozole to be well tolerated and safe over the length of follow-up. The trial outcomes have led to the approval of letrozole for the extended adjuvant indication in more than 40 countries worldwide. Re-randomization of letrozole-treated patients from this pivotal trial is underway to investigate if ten years of extended adjuvant endocrine therapy leads to further improvement, and the results of this extension study should aid in resolving several open questions regarding extended adjuvant therapy, including who should be treated and for how long.

Adjuvant endocrine therapy for postmenopausal women with early breast cancer

Results from multiple clinical trials involving aromatase inhibitors have added to the knowledge base relating to endocrine therapy of postmenopausal women with hormone receptor-positive early breast cancer. In the extended adjuvant setting, data from the Austrian Breast and Colorectal Cancer Study Group 6a trial showed an advantage for anastrozole following 5 years of tamoxifen treatment, consistent with the more robust MA.17 trial that examined letrozole versus placebo following 5 years of tamoxifen treatment. The combined analysis of the Austrian Breast and Colorectal Cancer Study Group 8 trial and the German Arimidex Nolvadex 95 trial, plus the Italian Tamoxifen Anastrozole trial, have shown the advantage of switching to anastrozole over continuing the tamoxifen to complete the full 5 years of adjuvant therapy. These trials support the previously reported larger and double-blind Intergroup Exemestane Study. The Arimidex, Tamoxifen, Alone or in Combination trial now has data out to 68 months of median follow-up showing the maintenance of a significant advantage of anastrozole over tamoxifen for disease-free survival. In this initial treatment setting, the Breast International Group 1-98 trial recently showed a significant advantage for letrozole over tamoxifen. The current debate is centered on whether the optimal strategy is to give an aromatase inhibitor initially or after several years of tamoxifen treatment. Multiple important questions remain, including the predictive value of molecular markers such as progesterone receptor, the optimal duration of aromatase inhibitor therapy, the long-term adverse effects, and the relative efficacy and toxicity of the different aromatase inhibitors.

Meeting Highlights: International Expert Consensus on the Primary Therapy of Early Breast Cancer 2005

The ninth St Gallen (Switzerland) expert consensus meeting in January 2005 made a fundamental change in the algorithm for selection of adjuvant systemic therapy for early breast cancer. Rather than the earlier approach commencing with risk assessment, the Panel affirmed that the first consideration was endocrine responsiveness. Three categories were acknowledged: endocrine responsive, endocrine non-responsive and tumors of uncertain endocrine responsiveness. The three categories were further divided according to menopausal status. Only then did the Panel divide patients into low-, intermediate- and high-risk categories. It agreed that axillary lymph node involvement did not automatically define high risk. Intermediate risk included both node-negative disease (if some features of the primary tumor indicated elevated risk) and patients with one to three involved lymph nodes without additional high-risk features such as HER 2/neu gene overexpression. The Panel recommended that patients be offered chemotherapy for endocrine non-responsive disease; endocrine therapy as the primary therapy for endocrine responsive disease, adding chemotherapy for some intermediate- and all high-risk groups in this category; and both chemotherapy and endocrine therapy for all patients in the uncertain endocrine response category except those in the low-risk group.