Most testicular cancer patients who try to father children after completing their treatment succeed, scientists said on Tuesday.

Men who have surgery to remove the tumor have the least problems but even patients who have radiotherapy and chemotherapy are able to have children.

"The vast majority of men, after testicular cancer treatment, can go on and have a family as normal," said Dr. Robert Huddart of The Institute of Cancer Research in London .

But he added that there is a portion of patients, regardless of what treatment they have had, who will have difficulty having children because the illness and low fertility are associated.

Cases of the cancer, which affects mostly men in their late 20s and early 30s, have risen rapidly in recent decades. In some countries it is the most common cancer among young men. About 50,000 new cases are reported worldwide each year.

Huddart and his colleagues studied 700 patients who had been treated for the disease between 1982-1992 and asked them to complete a questionnaire about their health and fertility. Their findings are published in the British Journal of Cancer.

Store sperm before treatment

Of the 200 patients who admitted they were trying to have a child, 77 percent were successful. An additional 10 percent fathered children through fertility treatment.

Men who had surgery and no follow-up treatment had an 85 percent success rate, followed by 82 percent for patients following radiotherapy and 71 percent after chemotherapy.

For patients who had both chemotherapy and radiotherapy the fertility rate dropped to 67 percent.

Despite the promising results, Huddart said men who want children should bank their sperm before having treatment.

"We would always advise men to bank their sperm before chemotherapy even though we would expect most of them to recover their fertility," Huddart said.

"Overall, it was under 5 percent of the men who wanted to have a family who needed that sort of support."

Testosterone monitored

If the disease is diagnosed and treated early, survival rates are very good. Six-time Tour de France winner Lance Armstrong suffered from the illness.

Denmark , Switzerland and Norway have among the highest rates of testicular cancer in the world. The disease is common is some families so researchers know there is a genetic component to the illness which accounts for about 20 percent of cases.

Doctors also suspect that environmental factors and exposure to higher levels of the female hormone estrogen in the womb are contributing factors to the increase in the disease.

The researchers suggested men's testosterone levels should be monitored because men with low levels tend to be less sexually active.

"We need to be alert for the men who have low testosterone because those men may be having a lower quality of life," Huddart explained.