New research suggests the risks of oral sodium phosphate solution and some oral sodium phosphate tablets are rare but real, particularly for elderly patients.

"People should be very cautious in the use of these agents because of their potential of causing kidney damage," said study author Dr. Anand Khurana, of the department of nephrology with the Scott & White Clinic at Texas A&M University in Temple, Texas.

The findings were published in the March 24 issue of the Archives of Internal Medicine.

Another popular prescription colonoscopy preparation -- polyethylene glycol solutions (PEG) -- was not the subject of the current study and does not appear to be associated with similar risks. Neither was the oral sodium phosphate tablet OsmoPrep, which has a lower sodium phosphate content than other tablets.

In 2006, the U.S. Food and Drug Administration put out an alert on oral sodium phosphate products, excluding OsmoPrep, recommending that they be "used with caution" among patients with impaired kidney function due to its high phosphate content.

The latest finding extends the concern to patients with no previous history of kidney trouble.

According to the American Cancer Society, colorectal cancer ranks third in the United States in terms of cancer diagnoses among both men and women. The organization estimates that about 150,000 people will develop the disease this year alone.

Typically, a colonoscopy is recommended for men and women over the age of 50 every 10 years as an effective way to screen for small growths called polyps and other signs of colorectal cancer. Some high-risk groups are encouraged to begin undergoing screenings at an earlier age.

The procedure involves the insertion of a slender and flexible lighted tube, fitted with a video camera, throughout the entire colon. A sigmoidoscopy relies on a similar but shorter tube to examine just the lower colon. Medication ensures that most patients feel no pain, and the screening is usually conducted on an outpatient basis.

However, patients must refrain from eating solid foods the day before the procedure, while also ingesting a bowel-cleansing liquid to clear out the colon.

The phosphate solution and tablets have been the preparations of preference because of convenience, as they are available without a prescription and require less clear liquid consumption than the polyethylene glycol solution.

To examine risks associated with use of the phosphate products, the authors analyzed kidney function among 268 patients at their clinic who had undergone either a colonoscopy or sigmoidoscopy between 1998 and 2005.

Most were white, with an average age of 68. Two-thirds were women, and none had a history of kidney disease. All the patients followed a standard dietary and phosphate solution prep the day prior to their screening.

Khurana and his team found that its use was associated with a 6 percent drop in kidney function six months later; that figure rose to 8 percent one year later.

"This magnitude of loss of kidney function is significant," said Khurana, who noted that patients undergo numerous colonoscopies over their lifetime, and normal kidney function loss is confined to about 1 percent per year among patients over 40.

Khurana pointed out that the safety risks he observed might ultimately be the result of patients simply not following manufacturer instructions to drink large amounts of clear liquid when consuming the preparation. Undetected chronic kidney disease among older patients undergoing colonoscopies might also play a role in the findings.

Nevertheless, "we believe that PEG preps are a safer option for patients" until further testing is done, he said.

Dr. Hemant K. Roy, an associate professor in the department of medicine at Evanston-Northwestern Healthcare in Illinois, described the findings as "quite alarming" in an accompanying editorial.

However, he stressed that warranted concerns about phosphate solutions should not discourage patients from undergoing colon cancer screening.

"Colonoscopies save lives," he stressed. "We know it works. So this should not dissuade people from doing one. I think we just need to be cautious about the type of preparation we use and who we give it to, so that an extraordinarily rare complication is avoided. And we have options, so there is a way to do that."

More information

For additional information on colonoscopies, visit the American Cancer Society.

While blacks who have an increased chance of developing colon cancer continue to lag behind their white counterparts in colonoscopy rates, the lack of a doctor referral stood out as the primary reason why high-risk patients of either race had not been screened.

For people who have close relatives that have been diagnosed with colon cancer, the recommended screening is a colonoscopy every five years after the age of 40.

"People with a family history of colon cancer have a two to four times increased risk of developing the disease compared with people who don't have such a history," explained lead researcher Dr. Harvey J. Murff, an assistant professor of medicine at Vanderbilt University in Nashville, Tenn.

"When you look at people who have more than one close relative diagnosed with colon cancer, African-Americans were about half as likely to have reported undergoing the appropriately recommended screening as compared to whites," Murff said.

The reasons for this disparity aren't clear, Murff said. It could be that doctors don't perceive blacks as having an increased risk for colon cancer, he speculated. It may also be that doctors are remiss in collecting a complete family medical history, he said.

"If providers aren't aware of family history, they may be less likely to recommend the test," Murff said. "There is a problem collecting family history and using it to risk-assess patients."

Other conditions that limit access to care, such as not having health insurance or a usual care provider, may also play a role, Murff said.

The report was published in the March 24 issue of the Archives of Internal Medicine.

In the study, Murff's group collected data on 41,830 people aged 40 to 79. Among these, 32,265 were black and 9,565 were white. The researchers specifically looked at how these patients were screened for colon cancer.

There were 538 blacks who reported having close relatives diagnosed with colon cancer, compared with 255 whites. Among blacks, 27.3 percent reported having a colonoscopy within the past five years, compared with 43.1 percent of whites.

The main reason for not having a colonoscopy among both blacks and whites was that their doctor had not recommended one. Among blacks, 59.3 percent said their doctor had not recommended a colonoscopy, compared with 51 percent of whites.

Doctors need to be sure that they get a complete family medical history, Murff said. "In addition, it is important for patients to know what your family history is, and if you have questions related to your family history or if you are concerned that it might impact your risk of disease, it is important to talk to your physician about it," he said.

More information

For more on disparities in cancer care visit the U.S. National Cancer Institute.

FRIDAY, Jan. 25 (HealthDay News) -- Patients who have had a colonoscopy can help encourage other people to undergo the screening for colorectal cancer, say University of Pennsylvania School of Medicine researchers.

They found that people who received telephone mentoring from a trained "peer coach" who'd had a colonoscopy were two times more likely to keep their first colonoscopy appointment than people who only received an educational brochure about colonoscopy or those who received no brochure or peer support.

The findings were published in the January issue of the Journal of General Internal Medicine.

"This study addresses an important gap in colorectal cancer prevention in the United States -- patients who don't follow through with their appointments," lead author Dr. Barbara J. Turner, a professor of medicine, said in a prepared statement. "This is one of the first studies to show that patients can help other patients overcome barriers to getting tests that can prevent this deadly disease."

Before they started calling patients, the five peer coaches in the study learned about communication strategies, colorectal cancer biology, screening modalities and potential barriers to colonoscopy.

The coaches, who used a scripted guide, called people who were scheduled to have a colonoscopy within two weeks.

The study found that almost 70 percent of people who received the telephone peer counseling kept their colonoscopy appointment, compared with 58 percent of those who only received an information brochure and 48 percent of people who received no brochure or peer support.

A follow-up found that 80 percent of patients who received telephone peer counseling found it "very helpful." Most appreciated hearing about another patient's colonoscopy experience and noted that they needed more information than was provided by their doctor.

More information

The U.S. National Institute of Diabetes and Digestive and Kidney Diseases has more about colonoscopy.

The marker, called colon cancer-specific antigen-2 (CCSA-2), could also differentiate between early- and late-stage disease, the researchers added.

The study was one of several concerning colon cancer being presented at the annual Gastrointestinal Cancers Symposium being held Jan. 25 to 27 in Orlando, Fla.

A second study found that patients who are uninsured or who have coverage with Medicaid tend to be diagnosed with colorectal cancer at a later stage than individuals with private insurance or Medicare. This is the first nationwide survey to confirm similar findings from smaller polls.

And a third study is a step on the road to so-called personalized medicine. "This study assesses the benefit of treatment with a monoclonal antibody for colorectal cancer patients based on their tumor's molecular signature," Dr. Nicholas Petrelli, an official with the symposium, said during a Wednesday teleconference on the findings.

According to the American Cancer Society, colorectal cancer is the third most common cancer among American men and women. Some 150,000 new cases are diagnosed each year in the United States.

Regular screening can catch the disease while it is still curable. Colon cancer can also be prevented if polyps and adenomas are found and removed before they become malignant.

There are already blood tests for colorectal cancer, but they result in false-positives in 60 percent to 90 percent of cases, depending on the test, said the authors of the first study.

The researchers, from Johns Hopkins University and the University of Pittsburgh, looked at 135 blood samples from individuals who had undergone colonoscopies. They were compared with samples from individuals with other types of cancer or with benign diseases.

Only about 20 percent of results were false positives, while only 9 percent of cancers went undetected.

There was also a correlation between the level of CCSA-2 in the blood and the size of the growth. The highest levels of CCSA-2 indicated the presence of actual cancer. The study was funded by Onconome, which has licensed the patent for the test from the University of Pittsburgh researchers.

The second study, conducted by the American Cancer Society, found that patients without health insurance were almost two times more likely and Medicaid patients 40 percent more likely to be diagnosed with stage II colon cancer rather than stage I disease, compared to those with Medicare or private insurance.

And again, uninsured patients were twice as likely while Medicaid patients were 50 percent more likely to be diagnosed with stage III or IV colon cancer than patients in the other insurance categories. The results held steady no matter where the cancer was found.

Minorities, females, older patients, those who lived in areas with low-income and low-education levels and those who were treated at non-research teaching hospitals were more likely to be diagnosed with advanced cancer.

"Improved access to screening and medical care in these populations may be able to reduce these disparities," said study author Dr. Michael Halpern, strategic director of health services research at the American Cancer Society.

And the third study confirmed that only patients who have a normal form of the KRAS gene in their tumors will benefit from the monoclonal antibody Vectibix (panitumumab). Mutations are found in 30 percent to 50 percent of colorectal cancer patients. The study was funded by Amgen, which makes the drug.

More information

Visit People Living With Cancer for more on colorectal cancer.

Before having a colonoscopy, you should follow certain do's and don'ts to ensure an accurate procedure. This list is provided by the U.S. National Digestive Diseases Information Clearinghouse:

• Avoid all solid foods and any beverages with food coloring for one to three days before a colonoscopy.
• You may eat fat-free bouillon or broth soups, or gelatin.
• You may drink water, strained fruit juice, plain coffee, plain tea or diet soda (no food coloring).
• As certain medications may affect your results, tell your doctor if you are taking aspirin, arthritis medications, blood thinners, medications for diabetes, or any vitamins containing iron.