A number of investigational cancer medicines that did not succeed in clinical trials, so-called "failures," are a critical part of the drug development process, according to a report by the Wash. D.C.-based Pharmaceutical Research and Manufacturers of America (PhRMA).

The report, Researching Cancer Medicines: Setbacks and Stepping Stones, illustrates the immense challenges in bringing new medicines to patients with cancer, and explores the factors that contributed to both the approvals of new treatments and those that "failed" between 1998 and 2014. The report focuses on three cancers particularly difficult to treat: melanoma, lung cancer and brain cancer.

Key findings include:

• 96 potential treatments for melanoma did not make it through clinical trials, but paved the way for seven approved medicines, a nearly 14:1 ratio of "failures" to "successes"
• 10 medicines have been approved to treat lung cancer, whereas 167 other potential treatments did not make it through clinical trials
• Only three new medicines have been approved to treat brain cancer, while another 75 investigational medicines were unsuccessful in the development process.

Despite these challenges, America's biopharmaceutical companies continue to invest in research to develop new treatments. According to the PhRMA report, there are 771 cancer medicines and vaccines either in clinical trials or awaiting review by the FDA. Of these medicines, more than 50 are for the treatment of melanoma, 98 for lung cancer and 47 for brain cancer.

"While it may sound counterintuitive, research setbacks are instrumental to furthering efforts to better understand a disease and how to treat it. They also are an indication of the incredible difficulty in developing medicines to treat cancer," said John J. Castellani, PhRMA president and CEO. "These setbacks serve as a reminder that to make progress, we need a public policy framework that supports drug development in combination with promising science so that we can bring important innovations to patients."

Significant advancements in the treatment of diseases like cancer typically are the result of cumulative innovation over time, rather than a single breakthrough in treatment. Every success—and every "failure"—builds on previous advances to improve patients' lives. Research has shown that cancer actually is a set of more than 200 extremely complex diseases and discovering medicines that effectively treat each one is a difficult task.

"While it is incredibly disappointing to see a promising new drug candidate eliminated from the pipeline, researchers take immeasurable learnings from every setback and build upon each one to develop effective therapies for patients," said Castellani.