TUESDAY, Feb. 8 (HealthDay News) -- Men who have had cancer are at a slightly higher risk of bearing children with congenital problems such as a cleft palate compared to their peers with no history of cancer, according to new research.

But the overall risk was low, researchers from Sweden report in the Feb. 8 online edition of the Journal of the National Cancer Institute.

And the findings are also reassuring to male cancer survivors who choose to conceive using assisted reproductive technologies (ART), as they have no additional risk over their peers who conceive naturally.

"The results of our study are reassuring in that men previously treated for cancer needing assisted reproduction to get children do not need to worry about [increasing] the risk of malformations in their children," said study co-author, Dr. Aleksander Giwercman, chairman of the Reproductive Medicine Centre and associate professor at Skane University Hospital, Lund University, Malmo, Sweden. "Furthermore, for this group of patients, in general, although the malformation risk in the offspring is indeed increased, this increase is only slight."

There has been concern that treatments such as chemotherapy and radiation might damage sperm DNA, although the effect is usually temporary.

As in this new study, previous research has found some -- but not much -- increased risk of congenital abnormalities among children of male cancer survivors. None of the earlier studies had looked specifically at ART, which some men use because of difficulties fertilizing an egg after their cancer. (ART includes such procedures as in vitro fertilization, in which fertilization of the egg and sperm occur outside the woman's body, and intracytoplasmic sperm injection, in which a single sperm is injected into the center of an egg to initiate fertilization.)

The study included 8,670 children who had been born in Sweden (between 1994 and 2005) and Denmark (between 1994 and 2004) to men who had a history of cancer. About 500 of these children were conceived using ART.

In addition, the study authors looked at over 1.7 million children who were born during the same time period to men with no history of cancer, of which almost 26,000 were conceived using ART.

Babies of male cancer survivors were 17 percent more likely to have a "major" congenital abnormality compared to babies born to healthy fathers, the investigators found.

However, the overall risk was very low: in absolute terms, it was only 3.7 percent among children of cancer survivors, compared to 3.2 percent for offspring of males without any history of cancer, regardless of mode of conception.

The risk seemed to be highest among men who had had skin, eye and central nervous system cancers, but there was no increased risk with testicular cancer, the researchers noted.

Children conceived using ART also had a 20 percent increased risk of major congenital abnormalities compared to children conceived normally, although the method of conception didn't affect the association between paternal history of cancer and birth defect risk.

There was also a slightly higher risk among men who conceived after the age of 18 and possibly for men who conceived within two years after their cancer diagnosis, but these were not "statistically significant," said Giwercman.

Though not proven yet, the authors indicated that the results suggest that the malignancy itself, as opposed to the treatments, is probably responsible for the abnormalities.

"We cannot say this for sure . . . however our preliminary results indicate that this is rather the cancer diagnosis per se and not the treatment by radio- and/or chemotherapy, which is the cause of slight increase in the malformation risk among the children," said Giwercman.

Besides the very low absolute risk of birth defects, the findings also suggest that a paternal history of cancer may not contribute to the "most adverse" defects, and that using ART may not worsen the risk, the researchers added.

In an accompanying editorial, co-author Lisa Signorello of the International Epidemiology Institute in Rockville, Md., noted that although more study is needed, the findings "are overall quite reassuring" for male cancer survivors.

More information

The Society for Assisted Reproductive Technology has more on these procedures.