TUESDAY, Sept. 20 (HealthDay News) -- The ever-improving treatments that are successfully helping cancer patients are also increasing the risk they will live long enough to develop second cancers, a study sponsored by the National Cancer Institute indicates.

The finding shows the need to develop effective cancer treatments that do less long-range damage, raising the possibility of a second cancer, said Dr. Charles F. Lynch, professor of epidemiology at the University of Iowa, and a member of the research team.

Cancer therapists are starting to meet that need, he said.

The study involved men who lived at least 10 years after a diagnosis of testicular cancer. And it found they had a substantially greater risk than the general population of having a cancer later in life, a risk that lasted for at least 35 years. The elevated risk was mostly due to the late side effects of treatment for the original cancer, according to the report published in the Sept. 21 issue of the Journal of the National Cancer Institute.

There have been other reports that reached similar conclusions, Lynch said, but "this is the largest cohort that has been put together looking at this, and one of the longest follow-ups."

The study used data on 40,576 survivors of testicular cancer from 14 tumor registries in North America and Europe. It found a slightly higher risk of a second cancer among men who had only radiation therapy as compared to those who had only chemotherapy.

A significant finding was that more than 30 percent of men treated at age 35 developed second cancers over the next 40 years, compared to the 23 percent cancer risk of the general population.

The most common second cancers were of the bladder, colon, lung, pancreas and stomach, and they accounted for 60 percent of the additional risk.

Testicular cancer affects predominantly young men, and the survival rate is high, in the neighborhood of 95 percent. The most prominent testicular cancer survivor is 34-year-old Lance Armstrong of Texas, seven-time winner of the Tour de France bicycle race.

But the study results also apply to a growing number of people who survive other forms of cancer, Lynch said. Aside from particularly deadly forms of malignancy, such as lung tumors, cancer is increasingly treatable, he said.

"The clinical implications are growing now that many more people survive a first cancer and live to get a second one," Lynch said. "These people can anticipate living for many years. The five-year survival rate for cancer is now over 50 percent."

The study researchers focused "on treatment for the first cancer, particularly on radiotherapy and chemotherapy," Lynch said. A problem with the newly reported research was a lack of information on exactly what treatments the survivors got -- how much radiation, how much chemotherapy, he said.

But Lynch sees reason for hope. "The bottom-line message is that in general, the treatments we have been using are less toxic," he said. "The second-cancer rates are going down. What we must do is find a cure for the first cancer but at minimum risk for second cancers."

More information

Learn more about testicular cancer and its treatment from the National Cancer Institute.