Diagnostic tests that look for specific genetic or molecular characteristics may be the key to helping doctors decide which lung cancer treatments work best for patients, two studies released on Wednesday suggest.

In one, researchers found AstraZeneca's lung cancer pill Iressa, or gefitinib, worked far better than chemotherapy in people from East Asia whose tumors had specific mutations in genes for the epidermal growth factor receptor or EGFR.

In another, a Spanish team found that people in Europe whose tumors also had mutations in the EGFR gene were more likely to be helped by Roche's erlotinib, brand name Tarceva, than other lung cancer patients.

Both studies, published in the New England Journal of Medicine, reinforce prior findings and offer new evidence that screening tests may be useful to match patients with the best therapy.

Given the fact that the cost of these drugs is exceedingly high ... I think we have to use them in selective subtypes, the ones most likely to respond, Dr. Adi Gazdar of the University of Texas Southwestern Medical Center, who wrote a commentary, said in a telephone interview.

If you can select out the right subtype, that is an important finding, and an important cost savings as well.

Gazdar said the findings in the East Asians were strong enough to suggest that Iressa might be effective as a first choice therapy for carefully selected patients.

IMPROVING ODDS

Drug companies and regulators increasingly are turning to so-called companion diagnostics -- tests that look for specific genes or proteins -- as a way to increase the odds a high-cost biotechnology drug will work in specific patients.

AstraZeneca stopped most U.S. sales of Iressa in 2004 after it was found to help only about 10 percent to 15 percent of lung cancer patients. But several studies have suggested that some people -- notably nonsmokers, Asians and women -- did better on Iressa.

In the latest study, Dr. Masahiro Fukuoka of Kinki University in Osaka, Japan, and Dr. Tony Mok of the Chinese University of Hong Kong and colleagues analyzed data on a group of 261 East Asians who had been nonsmokers or light smokers and whose tumors had the EGFR mutation.

Nearly 25 percent of people who had the mutations and who took Iressa survived a year without their cancer advancing, compared with just 6.7 percent of those who got chemotherapy.

Gazdar said while Iressa did not save any lives in the end, that may be because it is often not offered until other treatments failed. I think they make a good case that it should be used as first-line therapy, he said.

For the second study, a team lead by Dr. Rafael Rosell of the Catalan Institute of Oncology in Spain screened more than 2,100 patients with non-small cell lung cancer for EGFR mutations.

Like earlier studies in East Asians, they found people who had the mutations were more likely to respond to Tarceva. And it showed that diagnostic testing for EGFR mutations can be done quickly, and on a large scale, Gazdar said.

The evidence is building that there is potentially a particular benefit for the group of people who have EGFR mutations, said Charlotte Arnold, a spokeswoman for Genentech, now wholly owned by Roche.

She said Roche is conducting a late-stage study in Europe looking at the effectiveness of Tarceva as a first-line treatment for lung cancer patients with EGFR mutations. The study incorporates the use of a companion diagnostic test.

Tarceva, which costs about $3,600 per month, is already approved for lung cancer patients who have failed at least one round of chemotherapy.

Lung cancer kills 1.2 million people a year and is the top cause of cancer death globally.

Japan Medicine Cancer