MONDAY, July 19 (HealthDay News) -- Children conceived using in vitro fertilization have a higher risk of developing cancer than do children who were conceived naturally, new research shows.

While the study found the risk of cancer was increased by 42 percent for Swedish youngsters conceived with IVF, the absolute risk of cancer was still quite low.

"We found a roughly 50 percent increased risk for cancer in the IVF children, which means that if the risk without IVF is two per 1,000, it increases to three per 1,000 after IVF," explained study author Dr. Bengt Kallen, a professor emeritus in embryology at the Tornblad Institute at the University of Lund in Sweden.

The findings will be published in the August print issue of Pediatrics, but were posted online on July 19.

In vitro fertilization (IVF) is an assisted reproduction technology. Using eggs harvested from the prospective mother and sperm given by the prospective father, doctors can create human embryos that are then implanted into the mother's uterus.

Babies born using this technology are known to have an increased risk of birth defects and of birth complications, such as preterm birth. Previous research has also suggested that children born through this method of conception may also have an increased risk of cancer.

Using the Swedish Medical Birth Register, the researchers gathered information on almost 27,000 children who were born using IVF in Sweden from 1982 through 2005.

When they looked at the number of children who had cancer, they found that 53 children born from IVF had developed cancer compared to the expected rate of 38 cases of cancer in non-IVF children.

Other factors appeared to influence the risk of cancer as well. Children born before 37 weeks' gestation and those with a low birth weight, respiratory problems or a low Apgar score (a test given at birth to assess a newborn's health), had higher rates of cancer.

A mother's age, weight, smoking status and the number of miscarriages she'd already had didn't appear to affect a child's cancer risk. A multiple birth pregnancy also didn't appear to affect the risk of cancer.

Cancers of the blood, such as acute lymphoblastic leukemia, were the most common, affecting 18 children. The next most common were cancers of the eye or central nervous system, affecting 17 children.

Although it's not clear what's to blame for the increase, the study authors think it's unlikely that IVF is at the root of the increased risk of cancer.

"This study is interesting and thought-provoking, and it adds to our growing knowledge of potential IVF consequences," said Dr. David Cohen, chief of reproductive medicine at the University of Chicago.

"But, it's difficult to think what the biological plausibility would be. If it were something that occurs during the in vitro process or some substance in the media used, I would think that it would cause a much higher number of cancers. This may just be a statistical oddity," he added.

"This is the largest study that I'm aware of, and it does suggest an increased risk of childhood cancers ... but it doesn't really delineate whether it's the IVF process or the patient selection. Is this increase due to the procedure, or is it secondary due to a difference in the patient population?" said Dr. Edward Illions, a reproductive endocrinology specialist at the Montefiore Medical Center in New York City and the Montefiore Institute for Reproductive Medicine in Hartsdale, N.Y.

The three experts do not believe these findings will have a significant influence on a couple's decision to have the IVF procedure.

"The absolute risk is so small that it will hardly influence the decision to get an IVF," Kallen said.

"This adds more information to the [pre-IVF] counseling session, but I don't think it will change the decision. The absolute risk is still well less than 1 percent," said Cohen.

More information

Learn more about in vitro fertilization from the American Pregnancy Association  .

MONDAY, July 19 (HealthDay News) -- Exposure to cigarette smoke can undermine the immune system and raise the risk for cancer, cell death and metabolic problems by harming gene expression, new research reveals.

Gene expression is a crucial process in which a gene's information is changed into the structures and functions of a cell. The study, conducted by researchers from the Southwest Foundation for Biomedical Research (SFBR), uncovered the association by identifying links between the specific expression patterns of 323 genes (all located within white blood cells) among a pool of 1,240 people including 297 current smokers.

"Our results indicate that not only individual genes but entire networks of gene interaction are influenced by cigarette smoking," lead study author Jac Charlesworth said in a news release from SFBR. "The scale at which exposure to cigarette smoke appears to influence the expression levels of our genes is sobering."

Charlesworth, formerly of SFBR, is currently a research fellow at the Menzies Research Institute at the University of Tasmania in Australia. He and his colleagues published their findings online July 15 in BMC Medical Genomics.

The authors noted that their research, co-funded by the U.S. National Institutes of Health, is the largest study to date investigating smoking's effect on gene expression.

"It is likely that this observed effect of smoking on [RNA biosynthesis] has larger implications for human disease risk," Charlesworth added, "especially in relation to the increased risk of a wide variety of cancers throughout the body as a result of cigarette smoke exposure."

More information

For more on smoking and health risks, visit the American Cancer Society  .

FRIDAY, July 16 (HealthDay News) -- Being poorer and having co-existing health problems are among the reasons why black colorectal cancer patients have lower survival rates than whites or Asians in the United States, new study findings suggest.

In the study, researchers analyzed data from 37,769 Medicare beneficiaries diagnosed with stages I to III colorectal cancer between 1992 and 2002. Compared with Asians, who had the lowest risk of death, whites had a 26 percent higher risk of death, while blacks had a 56 percent higher risk, the study authors found.

Although being poorer and having other medical conditions ("comorbidities") partly explained worse survival rates among blacks compared with whites and Asians, a number of racial and ethnic differences in colorectal cancer survival persisted and weren't fully explained by variations in a number of factors looked at by the researchers.

Some of these factors significantly reduced the difference in death risk between whites and blacks, but didn't have an effect on the difference between blacks and Asians, according to the report, which was released online July 12 in advance of publication in an upcoming print issue of the journal Cancer.

"The results from this study will inform our progress towards eliminating health disparities and reducing the number of deaths from colorectal cancer," study leader Arica White, of the University of Texas School of Public Health at Houston, said in a news release from the journal's publisher. "It also sets the stage for future research to examine the role of socioeconomic status, comorbidities and other factors not included in this study."

Future research should assess the role of other factors related to quality of care, such as treatment and post-treatment surveillance, she added.

More information

The U.S. National Cancer Institute has more about colorectal cancer.

THURSDAY, July 15 (HealthDay News) -- Shielding the eye with silicon oil may safeguard the eyesight of patients who must undergo radiation therapy for an eye cancer known as ocular melanoma, new research suggests.

Although the study authors caution that more research is needed, they say that their current investigation reveals that the pre-radiation procedure appears to absorb about 50 percent of radiation rays that might otherwise hit the back and sides of the eye and cause irreversible damage.

"Vision loss is a devastating yet common side effect of radiation therapy," vitreoretinal surgeon Dr. Tara McCannel, an assistant professor of ophthalmology and director of the University of California Los Angeles (UCLA) Ophthalmic Oncology Center at the Jules Stein Eye Institute, said in a UCLA news release. "Until recently, physicians focused on killing the tumor and considered vision loss secondary. Our results suggest that silicon oil offers a safe tool for protecting the patient's vision during radiation," she added.

The finding is reported in the July issue of the Archives of Ophthalmology.

Ocular melanoma takes hold under the retina and is the most common adult eye cancer. Standard treatment involves the surgical application, and subsequent removal, of radioactive "seeds" to the white of the eye. Although effective at killing cancer cells, the process can also cause central vision loss by doing irreparable harm to optic nerve fibers and blood vessels.

"If patients survive the cancer, more than half will suffer vision loss in the treated eye six months to three years later," noted McCannel.

However, McCannel's team found that such risk can be significantly minimized by pre-surgical application of FDA-approved silicon oil shields around the interior of the eye. Post-surgery, the silicon is washed away with saline, and ultimately replaced by the patient's natural fluids.

The authors note that such silicon shields are already commonly used in retinal surgery. In addition, they found that the process does not hamper the effective use of radiation to attack tumor cells.

More information

For more on eye cancer, visit the American Cancer Society  .