The following article features coverage from the 2019 San Antonio Breast Cancer Symposium. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

Breast cancer drugs approved in the United States may lack substantial clinical benefit, particularly those used in the palliative setting, an analysis of clinical trials that support these drug approvals found. The analysis results were presented during a poster discussion at the 2019 San Antonio Breast Cancer Symposium (SABCS) in Texas.

Using the Drugs@FDA website, study researchers identified 18 breast cancer drugs that were approved between January 1, 2006, and June 30, 2019. The approved drugs spanned 24 indications and were supported by 28 pivotal clinical trials. Most of the trials (79%) were for the palliative setting and the rest (21%) were for the curative setting.

The study researchers used the following validated tools to quantify the clinical benefit of cancer drugs: the American Society of Clinical Oncology (ASCO) Cancer Research Committee (ASCO-CRC), the ASCO Value Framework Net Health Benefit score version 2 (ASCO-NHB v2), and the European Society for Medical Oncology-Magnitude of Clinical Benefit Scale version 1.1 (ESMO-MCBS v1.1). Substantial clinical benefit was defined according to criteria for each validated tool. 

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Using these validated tools, the study researchers found a varying proportion of trials that achieved the established threshold of substantial clinical benefit. 

For trials in the palliative setting, the proportion of trials that showed substantial clinical benefit ranged from 23% with ESMO-MCBS v1.1 to 79% with ASCO-CRC; according to ASCO-NHB v2, 45% of trials showed a substantial clinical benefit. For trials in the curative setting, the proportion of trials that showed substantial clinical benefit ranged from 25% with ASCO-NHB v2 to 80% with ESMO-MCBS v1.1.

In addition, only 9% of trials in the palliative setting showed a considerable overall survival (OS) benefit, whereas no trials in the curative setting showed an extensive OS benefit. Also, among the trials that reported quality of life (QoL) measures, 60% in the palliative setting and none in the curative setting showed a QoL benefit. 

“Perhaps these findings weren’t terribly surprising,” said study discussant Michael Hassett, MD, MPH, Dana-Farber Cancer Institute, Boston, Massachusetts, on the study group’s results evaluating drug benefit in the palliative and curative settings. One reason for this is that initial drug evaluations often focus on patients with advanced disease, he said. “These are the folks for whom value is least likely to be demonstrated because outcomes are hardest to improve.”

In metastatic disease, the analysis found that “most FDA approval trials do not meet the ASCO-NHB v2 and ESMO-MCBS v1.1 thresholds for substantial clinical benefit.” The authors also wrote in the abstract that “in patients with early breast cancer, low agreement observed between the ASCO-NHB v2 and ESMO-MCBS v1.1 suggest that the respective frameworks may require additional refinement to accurately capture substantial clinical benefit in the curative setting.”

The analysis also revealed that, according to ESMO-MCBS v1, drugs that were approved with a companion diagnostic had a higher likelihood of having a substantial clinical benefit (odds ratio, 18.23; 95% CI, 1.56-212.49; P =.020). The other validated tools did not show such an association. 

Read more of Cancer Therapy Advisor‘s coverage of SABCS by visiting the conference page.

Reference

  1. Tapia JC, Molto C, Bujosa A, et al. Clinical benefit of breast cancer drugs approved by the United States Food and Drug Administration. Poster presentation at: 2019 San Antonio Breast Cancer Symposium; December 10-14, 2019; San Antonio, TX. Abstract PD10-06.