New stomach cancer therapy potentially more convenient and better tolerated

Data suggest that it may pack an improved punch against gastric cancer

A new combination chemotherapy appears to battle advanced stomach cancer harder than other platinum-based therapies, while offering patients more convenience and potentially less discomfort, according to results announced at the 2005 Annual Meeting of the American Society of Clinical Oncology. Researchers studied the combination of a new drug, called S-1, and the platinum-based chemotherapy called cisplatin in patients with advanced gastric cancer.

Overall, 13 of the 20 patients (65 percent) evaluated so far in the phase II trial responded to the chemotherapy. That means tumors shrank in response to the drug. “We believe the therapy has the potential to not only fight cancer more effectively, but also is easier for cancer patients to deal with,” says study co-author and medical oncologist Heinz-Josef Lenz, M.D., associate professor of medicine at the Keck School of Medicine of the University of Southern California and USC/Norris Comprehensive Cancer Center.

The study was presented at ASCO by Jaffer A. Ajani, M.D., professor in gastrointestinal medical oncology at University of Texas/M.D. Anderson Cancer Center.

In 2005, experts estimate that 21,860 Americans will be diagnosed with stomach cancer during 2005 and another 11,550 will die from the disease.

In addition to surgery, physicians today use a variety of chemotherapy drugs against stomach cancer. Yet researchers have not found a standard chemotherapy regimen that dramatically improves survival more than any other.

One commonly used drug is the traditional chemotherapy called 5-FU (5-fluorouracil). Studies have shown that when cisplatin is combined with 5-FU, cancer shrinks in 46 percent to 51 percent of stomach cancer patients. The combination of S-1 and cisplatin aims to take that a step further.

S-1 consists of a number of parts. One portion of S-1 actually breaks down into 5-FU in the body. At the same time, it contains another element that keeps levels of 5-FU fairly steady in the body, reducing the ups and downs of chemotherapy. It contains a third element, too, that fights 5-FU’s toxic effects in gastrointestinal tissues-a cause of chemotherapy nausea and vomiting. Finally, it is available in a capsule, instead of through an intravenous infusion, making it more convenient for patients.

In this study, patients received an infusion of cisplatin on the first day of treatment, then took S-1 twice a day every day for three weeks, and took a week off to recover before starting the cycle all over again.

In all, 41 patients participated and were evaluable; researchers have examined information on the drug’s safety in 30 patients and on the drug’s effectiveness in 20 patients. In the 13 patients whose cancer responded to the drug, tumors began growing again about 4.8 months after treatment.

Lenz is optimistic about the drug’s potential. “At USC/Norris, we established the genetic profile giving the rationale for this drug, so we understand how and why it works,” he says. He noted that another early study in Japan of S-1 and cisplatin for advanced gastric cancer showed 19 of 25 patients, or 76 percent, responded to the drug.

The most common side effects were fatigue, nausea and anorexia.

S-1 is under development by Taiho Pharma USA Inc.