Lung and pancreatic cancer patients treated with a certain drug who develop a rash live longer, according to a study from the drug's maker.

Patients who got a moderate or severe acne-like rash survived 245 percent longer than those with less severe skin problems, after taking erlontinib, sold as Tarceva by OSI Pharmaceuticals Inc.

Researchers found that in the majority of cases, the more severe the rash, the longer a patient's cancer was held in check, the company said.

A company official said that knowing about the rash is important, because it was unpleasant enough that some people wanted to stop treatment.

"Some patients are stopping treatment because of the rash, yet those are the ones who are most likely to benefit," said Bret Wacker, leader author of the study.

According to the researchers, these rashes can be controlled with mild steroids or antibiotics, and in most cases, they will improve with treatment. They are believed to be due to an inflammatory response as a result of the drug's action.

The report was based on studies that included placebos, control groups and doctors and patients who did not know who received the treatment. This kind of study is believed to produce the most reliable results.

In the study of 673 patients, 81 percent taking Tarceva got a rash. Eighteen percent of the placebo group had that reaction. Survival was also longer in that group. That could be due to a stronger immune system, doctors said.