U.S. and Japanese Patients With NSCLC Respond Differently to Chemotherapy

June 5, 2004

A new study shows that paclitaxel (Taxol) is more effective but also more toxic in Japanese patients with advanced stage non-small cell lung cancer (NSCLC) than in U.S. patients. Non-small cell lung cancer is the most common type of lung cancer.

To address differences in study results from country to country, doctors from the Japanese Four Arm Cooperative Study (FACS) and the Southwest Oncology Group (SWOG) in the United States designed separate, parallel phase III trials for the treatment of NSCLC. One group of patients in each trial received the same treatment - a combination of paclitaxel and carboplatin. Because the dose of paclitaxel the patients received was based on previous phase I studies, the Japanese patients received 200 mg/m² and the American patients received 225 mg/m².

The study found that the characteristics of the patients (such as age, ratio of men to women, stage, and type of cancer) enrolled in Japan were statistically identical to those of the patients enrolled in the United States. But, the response to treatment was different. After one year of treatment, 51% of the Japanese patients were living, compared with 37% of the American patients. The Japanese patients were also 2.5 times more likely to experience severe neutropenia (low white blood cell count) and almost five times more likely to experience neutropenia accompanied by a fever than U.S. patients.

"Results of a cancer clinical trial performed in one part of the world may not necessarily hold true for populations in another region," said lead author David Gandara, MD, Director of Clinical Research at the University of California, Davis Cancer Center and Professor of Medicine at the University of California, Davis School of Medicine. "Compared to the relatively homogenous population in Japan, the United States is very diverse. When we examine studies, we have to take these population-related differences into consideration."

Dr. Gandara and his fellow researchers think that genetic differences in the way people's bodies break down drugs may explain these results, and that this effect may be why the response to cancer treatments varies in different parts of the world.

What This Means For Patients

The study demonstrates that people from different countries can have different responses to treatment, such as chemotherapy, than patients in the United States. This result may help doctors interpret clinical trial results from countries outside the United States.