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The Next Generation of Breast Cancer Prevention:
Clinical Trial Background for NSABP P-4

The Study to Evaluate Letrozole and Raloxifene (STELLAR), or NSABP P-4, is a clinical trial that represents an opportunity to dramatically reduce the toll of breast cancer. With 175,000 women diagnosed with invasive beast cancer each year – and 40,000 women dying each year from the disease – NSABP P-4 is designed to evaluate the efficacy of letrozole, a drug that shows the potential to reduce breast cancer incidence by more than 70%.

NSABP P-4 Review and Approval Process To-Date

Fall 2005
NSABP submitted the NSABP P-4 study concept to the NCI’s Division of Cancer Prevention.

October 2005
The NCI’s Executive Committee reviewed and approved the NSABP P-4 study proposal.

May 2006
The NCI’s Clinical Trials Operations Committee (CTOC) and a Special Emphasis Panel approved the trial proposal.

October 2006
The NCI’s Division of Cancer Prevention conditionally approved the full NSABP P-4 protocol, pending review by the U.S. FDA.

December 2006
Full competitive renewal of the NSABP Community Clinical Oncology Program (CCOP) Research Base award (which included the P-4 study) underwent peer review at the NCI and was awarded a priority score of 131 – the best grant proposal score in the nearly 50- year history of NSABP. A Special Emphasis Panel recommended that the NSABP receive approximately $66 million in direct funding over a five-year period for NSABP P-4, with $12.3 million recommended for Year 1.

December 2006
The U.S. FDA provided approval for the NSABP to proceed with the NSABP P-4 trial.

January 2007
The NCI’s Executive Committee issued the agency’s final approval to proceed with the trial on the 22nd. The following day, NCI Director Niederhuber placed the study on hold and continues to delay commencement of the trial.

March 2007
Dr. Niederhuber convened an ad hoc expert panel to further discuss the P-4 trial in an unusual, closed-door session. The same month, prior to the ad hoc panel meeting, Dr. Niederhuber indicated in an interview with the Cancer Letter “it is unlikely that the trial would open this year, if at all.”Health Canada provided approval for the NSABP to proceed with the NSABP P 4 trial at sites located throughout Canada.

June 2007
The report of the ad hoc panel was presented to the NCI National Cancer Advisory Board (NCAB) on Thursday, June 14th. Dr. Niederhuber issued his decision on Tuesday, June 19th stating that “the NCI will not commit to the funding of this particular trial.”

The NSABP P-4 Trial
  • NSABP P-4 would be the third in a series of trials for breast cancer prevention.
    • In 1998, NSABP P-1 found that tamoxifen prevented invasive breast cancer in 49 percent of participants.
    • In 2006, NSABP P-2 found that tamoxifen and raloxifene were equivalent in reducing invasive breast cancer among high-risk trial participants, but raloxifene resulted in fewer serious side effects.
    • Combined, the two trials provided risk assessments to more than one quarter of a million women, with roughly one million more receiving important educational information at our trial sites.
  • The NSABP P-4 trial will require four years to accrue 12,800 participants at high risk for developing breast cancer and an additional two-to-three years of follow-up prior to analysis of the study data.
  • The study would help identify the differential benefits and risks of letrozole and raloxifene, two alternative therapies for breast cancer prevention, among high-risk, post-menopausal women to help them make smarter choices in their fight against this disease.

NSABP Heritage of Breast Cancer Treatment and Prevention
  • Since 1971, the NSABP has played a vital role in improving and setting the standard for breast cancer treatment and prevention.
  • Funded by the NCI, the group has conducted large-scale clinical trials at nearly 200 institutions—and 300 satellite centers—throughout the U.S. and four other countries, enrolling more than 110,000 individuals in breast cancer trials to date.
  • In the 1970s, the NSABP showed that a total mastectomy was as effective in treating breast cancer as a radical mastectomy; the NSABP went on later to prove lumpectomy was an effective alternative to mastectomy.
  • The NSABP has been successfully conducting breast cancer prevention trials since 1992, advancing the knowledge base and testing new prevention options through its clinical trials.
  • Because of the prior breast cancer prevention research trials, an estimated 750,000 women are more aware of their personal risks for developing breast cancer and are aware of what options are available to them; this effort has significantly improved the public health of the nation.