A new targeted drug demonstrated its ability to control metastatic gastrointestinal stromal tumor, an uncommon and life-threatening form of sarcoma, after the disease had become resistant to all existing therapies, report investigators at Dana-Farber Cancer Institute who led the worldwide clinical trial.
The treatment of gastrointestinal stromal tumor, or GIST, even in its advanced metastatic stage, has been dramatically improved with two oral targeted drugs - imatinib (Gleevec) and sunitinib (Sutent). To date, these have represented the only two FDA-approved treatments with the proven ability to control GIST. However, in more than 85 percent of patients, GIST becomes resistant to these drugs after seven years and the disease worsens with fatal results.
The new study, whose results are being published in the Lancet, demonstrated that the oral drug regorafenib, which inhibits several cancer-promoting kinase enzymes, was able to control GIST for nearly four months longer than placebo in patients for whom Gleevec and Sutent were no longer effective, a result that was highly significant statistically.
"When added to best supportive care, regorafenib significantly improves disease control, as measured by progression-free survival time in patients with GIST after progression which represents failure of all other therapies," said George Demetri, MD, of Dana-Farber, principal investigator of this clinical trial.
Demonstrating the aggressive nature of this resistant disease, the study found that tumors objectively grew in less than a month, on average, in GIST patients who were initially randomized to receive a placebo. The study's "cross-over" design made it possible to treat those patients whose tumors grew, and 85 percent of the patients initially on placebo were able to receive regorafenib, which then controlled the disease in these patients as well.
Because of the study's cross-over design, Demetri said, it was not expected to prove that the patients initially randomized to receive regorafenib survived longer - the researchers would have had to withhold the drug from the placebo patients to demonstrate that difference. "But there is no question that people are living longer" with regorafenib treatment, he said, based on the results of this trial.
An application to have regorafenib approved for use in resistant GIST is under an accelerated review by the Food and Drug Administration, Demetri said.
GIST is a rare form of sarcoma that develops in the gastrointestinal tract, mainly in the stomach and small intestine. GIST is estimated to affect more than 5,000 people per year in the United States and about 8,000 in Europe.
Regorafenib is a novel rationally designed drug manufactured by Bayer HealthCare Pharmaceuticals that was FDA-approved in September 2012 to treat metastatic colon cancer after failure of standard chemotherapy. It blocks several cancer-promoting enzymes called kinases, which spur runaway growth in GIST and other cancers.