To try to understand why chemotherapy kills some tumors more effectively than others, Dallas researchers and their colleagues have delved into the individual characteristics of lung tumors.

Their study is part of a growing trend in cancer research to personalize treatments, matching them to each patient's tumor. "We should have individualized therapy rather than mass therapy off the shelf," said Dr. Adi Gazdar, the lung cancer specialist at UT Southwestern Medical Center who led the new study.

The study, which appeared last week in the journal PLoS Medicine, was conducted to help explain why lung cancer patients of East Asian descent often respond better to chemotherapy than other ethnic groups do.

Many lung cancers are fueled by a gene, known as EGFR, that drives cell division. Two drugs used to treat lung cancer, Iressa and Tarceva, are aimed at blocking the effects of the EGFR gene. Doctors have found that people of East Asian descent respond much better to the drugs, although their tumors later develop resistance. Studies have suggested that the good initial response is caused by mutations in the EGFR gene within the tumor cells themselves. The mutations allow the drugs to work more effectively.

In the new study, Dr. Gazdar and colleagues tried to figure out why East Asians are more likely to develop those mutations and be more responsive to the drugs. The scientists studied genes from healthy people of various ethnicities and more than 500 samples of normal and cancerous lung tissue. East Asians in the study were from Taiwan, Korea, Japan, Hong Kong and China.

The researchers found a complex genetic scenario they say may explain why East Asians are more likely to develop the mutations. East Asians are more likely than Caucasians (the group that served as a comparison) to start with what seems to be a weaker form of the EGFR gene. So the East Asians' tumor cells may be more likely to develop mutations as a way to make up for that weaker gene. East Asians were also more likely to harbor extra copies of the gene in their tumor cells, another genetic glitch that would make up for the weaker gene.

Currently, doctors test for the mutations in lung tumor cells to determine who should get the two drugs. Dr. Gazdar said his study suggests that testing for the extra copies of the gene as well as the presence of the weaker gene might be beneficial, too.

"A further understanding of the gene alterations and how they relate to ethnicity will help refine who is going to benefit from therapy," said Pasi Jänne, a cancer researcher at the Dana-Farber Cancer Institute in Boston who commented on the study.

Researchers are also making strides in figuring out how tumors become resistant to chemotherapy. In a report published in Friday's issue of the journal Science, Dr. Jänne reported on genetic changes that make lung cancer cells resistant to Iressa.

Extra copies of a gene called MET make lung cancer cells resistant to the drug. Blocking the effects of the MET gene made lung cancer cells sensitive to the drug once again, Dr. Jänne said.

Other UT Southwestern researchers who participated in the study of East Asians were Masaharu Nomura, Hisayuki Shigematsu, Makoto Suzuki, Takao Takahashi, Pila Estess, Mark Siegelman, Jerry Shay, and John Minna. Researchers from Seattle, Houston, Tokyo and Italy also participated.