TUESDAY, Aug. 4 (HealthDay News) -- Periodically cutting calories may lower the risk of developing breast cancer better than full-time dieting, according to a new study published in Cancer Prevention Research.

Three sets of mice predisposed to developing breast tumors were put on different diets: unlimited eating, intermittently cutting calories by 25 percent, or permanently reducing caloric intake 25 percent. Those on the intermittent diet fared best, with only 9 percent developing mammary tumors compared to 35 percent of those chronically restricted and 71 percent of those that ate all they wanted.

Although previous studies had shown similar results, the researchers were still surprised. Study author Margot P. Cleary, a professor at The Hormel Institute of the University of Minnesota, said her team thought periodic dieting might foster tumor growth as the return of added nourishment could jumpstart the secretion of insulin-like growth factor 1 (IGF-1), a hormone linked to the promotion of breast cancer.

"Understanding how calorie restriction provides protection against the development of mammary tumors should help us identify pathways that could be targeted for chemoprevention studies," she said in a news release. "Further identification of serum factors that are involved in tumor development would possibly provide a way to identify at-risk individuals and target interventions to these people."

This study "contributes to accumulating evidence that caloric restriction acts by altering hormone levels rather than by directly starving cancers of energy," Dr. Michael Pollak, a professor of oncology at McGill University in Montreal, wrote in an accompanying editorial. "In particular, lower levels of insulin are associated with reduced food intake, and this may be protective," he said.

Finding ways to reduce IGF-1 and insulin in the body, medically or though diet and exercise, should be further investigated, Pollak suggested.

More information

The National Cancer Institute has more about breast cancer.

MONDAY, Aug. 3 (HealthDay News) -- Common variants of a gene that determines blood type are associated with an increased risk of pancreatic cancer, according to U.S. researchers.

They studied the genomes of more than 4,300 pancreatic cancer patients and more than 4,500 people without the disease. This analysis found that people with variants of the ABO gene that produce the blood types A, B or AB are associated with increased risk of pancreatic cancer. Those with blood type O aren't at increased risk for the disease, the researchers noted in the report published online Aug. 2 in the journal Nature Genetics.

The findings are consistent with previous research that showed an increased risk of pancreatic and gastric cancer among people with blood types A, B and AB, according to a news release from the U.S. National Cancer Institute.

"Although it will take much more work, this finding may lead to improved diagnostic and therapeutic interventions that are so desperately needed," study co-author Patricia Hartge, of the division of cancer epidemiology and genetics at the U.S. National Cancer Institute, said in the news release.

Pancreatic cancer, the fourth-leading cause of cancer death in the United States, is hard to detect. Many patients are not diagnosed until the disease has spread to other parts of the body. Fewer than 5 percent of patients survive for five years. Pancreatic cancer risk factors include diabetes, smoking, race and family history of the disease.

More information

The American Cancer Society has more about pancreatic cancer  .

THURSDAY, July 30 (HealthDay News) -- Infection with the human papillomavirus (HPV) may improve survival in patients with head and neck cancer, U.S. researchers report.

They said the finding may explain why black Americans, who have far less HPV infection than whites, have poorer head and neck cancer survival rates.

"There is currently no consensus on why blacks fare worse with squamous cell carcinoma of the head and neck than whites, but this is the first clue that it may be biologic rather than related to issues of access, insurance or provider attitudes," senior study author Dr. Kevin Cullen, director of the University of Maryland's cancer center and a professor of medicine at the University of Maryland School of Medicine, said in a news release from the American Association for Cancer Research.

Cullen and his colleagues found that median overall survival was 70.6 months for white patients and 20.9 months for black patients treated with chemotherapy and radiation. Median survival was 26.6 months for HPV-negative patients, while the survival rate for HPV-positive patients couldn't be calculated because most were still alive.

Four percent of black patients and 34 percent of white patients were HPV-positive, the researchers found.

The study appears in the July 29 online edition of Cancer Prevention Research.

The findings may prove "practice-changing," according to Dr. Scott Lippman, editor-in-chief of Cancer Prevention Research and chairman of the Department of Clinical Cancer Prevention at the University of Texas M.D. Anderson Cancer Center.

"Squamous cell carcinoma of the head and neck is one of the fastest- growing cancers, and this study gives us a new way to assess prognosis for our patients," Lippman said in the news release.

More information

The U.S. National Cancer Institute has more about head and neck cancer.

WEDNESDAY, July 29 (HealthDay News) -- Increased oxygen consumption associated with moderate- to high-intensity exercise appears to reduce the risk of cancer, a new study has found.

The Finnish study included 2,560 men, aged 42 to 61, whose leisure-time physical activity was assessed over one year. None of the men had a history of cancer, according to the report published online July 28 in the British Journal of Sports Medicine.

During an average follow-up of 16 years, 181 of the men died from cancer. Those who engaged in moderate- to high-intensity exercise for at least 30 minutes a day were 50 percent less likely to develop cancer compared with the other men.

The researchers found that an increase of 1.2 metabolic units (oxygen consumption) was related to a decreased risk of cancer death, especially in lung and gastrointestinal cancers, after they took into account factors such as age, smoking, alcohol consumption, body mass index, and fiber/fat intake.

"The intensity of leisure-time physical activity should be at least moderate so that beneficial effect of physical activity for reducing overall cancer mortality can be achieved," the study authors wrote in a news release.

More information

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