Femara shows reduced risk of death versus tamoxifen after breast cancer surgery

Dec 14 2008

Femara showed reduced risk of death by 13% (P=0.08) versus tamoxifen, despite inclusion of patients who had switched over from tamoxifen to Femara during the study period, following the study's unblinding.

• In a separate censored analysis excluding patients after they crossed over to Femara, reduction in risk of death was 19% (HR= 0.81, 95% CI: 0.69-0.94)
• Long-term follow-up from major independent BIG 1-98 trial adds further evidence that starting with Femara may be the optimal treatment strategy versus tamoxifen

New long-term data from a major international breast cancer study reports that postmenopausal woman with hormone receptor-positive early-stage breast cancer who took Femara (letrozole) for five years following surgery had a 13% (P=0.08) reduced risk of death, when compared with tamoxifen.

These results are from a protocol-defined Intent-to-Treat (ITT) analysis (median follow-up of 76 months) of the Femara and tamoxifen monotherapy arms in the Breast International Group (BIG) 1-98 study. The suggested survival benefit from the ITT analysis is important considering that approximately 25% of patients in the tamoxifen arm selectively crossed over to Femara therapy after the tamoxifen arm was unblinded in 2005. While not statistically significant, these are the first data to suggest a survival benefit for an aromatase inhibitor versus tamoxifen in the monotherapy setting immediately following surgery.

To explore the impact of the selective crossover, an additional analysis was conducted censoring follow-up times at the date of crossover to letrozole for 25% of the patients in the tamoxifen arm. In this analysis, a 19% reduction in risk of death (HR=0.81, 95% CI: 0.69-0.94) was observed in favour of Femara.

The International Breast Cancer Study Group (IBCSG) today presented these results from the BIG 1-98 trial at the 31st Annual CTRC-AACR San Antonio Breast Cancer Symposium (SABCS), an international scientific symposium for scientists and clinicians in breast cancer.

"These data represent an important milestone in the treatment of women with breast cancer. For the first time we are seeing suggested survival benefit with upfront aromatase inhibitor (letrozole) therapy for five years compared with tamoxifen for the same time period," said Professor Nigel Bundred, Professor of Surgical Oncology, University Hospital of South Manchester NHS Foundation Trust.

Also commenting on the study, PhD, Henning T. Mouridsen, MD, Professor of Oncology, Copenhagen University Hospital and one of the investigators of the BIG 1-98 trial said; "The potential reduction in the risk of death that we are seeing with letrozole in the adjuvant setting may be a positive result of letrozole's early and sustained reduction in the risk of recurrence and distant metastases."

BIG 1-98 is the only clinical trial designed to explore both a head-to-head comparison of an aromatase inhibitor with tamoxifen during the first five years following breast cancer surgery and the sequencing of both agents to determine the most effective approach to minimizing the risk of recurrence. In the initial adjuvant setting, Femara is the only aromatase inhibitor to have demonstrated an early significant reduction in distant metastases versus tamoxifen, at a median duration of follow-up of 26 months.

Beyond the potential survival benefit of 13% (P=0.08, HR=0.87, 95% CI: 0.75-1.02) reduction in risk of death for Femara patients seen in the ITT analysis, Femara demonstrated significant long-term benefit in reducing the risk of disease free survival events by 12% (P=0.03, HR=0.88, 95% CI: 0.78-0.99) and reducing the risk of distant metastases by 15% (P=0.05, HR=0.85, 95% CI: 0.72-1.00) compared with tamoxifen.

"Femara has consistently demonstrated remarkable results and these data reaffirm the benefit of Femara for postmenopausal women with early-stage breast cancer," said Alessandro Riva, MD, Executive Vice President, Head of Global Development at Novartis Oncology. "The survival data shown may offer new promise for breast cancer patients."

Also presented at the meeting were results from the Sequential Treatment Analysis (STA) of BIG 1-98 which revealed that sequencing hormone therapy following surgery is not superior to five years of Femara alone.

The five-year disease-free survival rates for the three groups of patients in the STA were 87.9% for those patients receiving Femara only, 86.2% for those patients receiving two years of tamoxifen followed by three years of Femara and 87.6% for those patients receiving two years of Femara followed by three years of tamoxifen. The study investigators conclude that sequential treatment does not improve disease free survival compared with Femara alone.

This Phase III, randomized, double-blind, controlled clinical trial enrolled postmenopausal women with early breast cancer, in 27 countries1.

Patients were randomly assigned one of four treatment regimens: (1) five years of tamoxifen only; (2) five years of Femara only; (3) two years of tamoxifen followed by three years of Femara; (4) two years of Femara followed by three years of tamoxifen. In 1998 the first cohort began enrolling patients to receive either Femara or tamoxifen alone. In 1999, the second cohort (solely contributing to the Sequential Treatment Analysis) began enrolling patients to receive Femara or tamoxifen alone, tamoxifen followed by Femara or Femara followed by tamoxifen (n=6,182 patients). Combined, the monotherapy arms of the trial included 4,922 patients who were randomly assigned either Femara or tamoxifen treatment1. The Primary Core Analysis, reported in 2005, included all 8,010 patients enrolled in the trial.

The primary study endpoint of the study was disease-free survival (DFS), defined as the time from randomization to the first of one of the following events: recurrence at local, regional, or distant sites; a new invasive cancer in the contralateral breast; any second, non-breast cancer; or death without a prior cancer event, which is similar but not identical to the endpoint definitions used in other AI adjuvant trials. Other endpoints included time to breast cancer recurrence [including invasive contralateral breast cancer, ignoring second (non breast) malignancies, and censoring deaths prior to cancer event], time to distant breast cancer recurrence (time to breast cancer recurrence but ignoring local, regional and contralateral breast events), and overall survival.

In 2005, following initial results showing superiority of Femara monotherapy over tamoxifen monotherapy in improving disease-free survival and reducing the risk of recurrence, the tamoxifen-only treatment arm was unblinded and approximately one quarter of those patients selectively crossed over to Femara treatment. The other three treatment arms remained blinded. Subsequent analyses were designed to estimate the extent to which the crossover affected the comparative benefit of Femara1.

With the long-term follow-up in the analysis conducted more than 10 years after the start of the study, adverse events for Femara and tamoxifen were found to be consistent with the known safety profiles of both drugs. Patients will be monitored for the rest of their lives to track disease status, safety and overall survival(2).

Femara is a once-daily oral aromatase inhibitor available in more than 100 countries, including the US, major European countries and Japan. It is approved for a number of indications in the UK:

• Adjuvant treatment of postmenopausal women with hormone-receptor-positive early breast cancer
• Extended adjuvant treatment of hormone-dependent early breast cancer in postmenopausal women who have had prior standard adjuvant tamoxifen therapy for five years
• First-line treatment in postmenopausal women with hormone-dependent advanced breast cancer
• Advanced breast cancer in women with natural or artificially induced postmenopausal status after relapse or disease progression who have been treated with antiestrogens
• Pre-operative therapy in postmenopausal women with localized hormone receptor-positive breast cancer which allows subsequent breast-conserving surgery in patients not originally considered suitable for this type of surgery