Environment, not ‘bad luck’, mainly to blame for cancer

Screening may cut ovarian cancer deaths

PARIS, Dec 18, (Agencies): Environmental factors such as sunshine and tobacco smoke cause more cancers than random DNA mutations, researchers have affirmed -contesting another team’s conclusions that “bad luck” was mainly to blame.

The study, published in the journal Nature on Wednesday, was conducted to challenge a controversy-stirring paper carried by US-based Science in January, which said unavoidable errors in gene coding was the main cancer cause.

The latest work -- based on several mathematical analyses of cancer data -- found “strong evidence” that random errors that occur during DNA replication contributed “only modestly” to the development of many common cancers.

Seventy to 90 percent, in fact, were caused by environmental factors such as ultraviolet radiation, the team found.

Other experts not involved in the study cautioned against reading too

much into the results.

“Their analysis supports conventional thinking around cancer formation and development, and casts doubt on the idea that some cancers are relatively independent of how you live and what you’re exposed to,” Andrew Maynard of Arizona State University wrote in a comment.

But the findings were not definitive, he said, and were based on a number of assumptions that may have influenced the conclusions.

Giles Hooker from Cornell University in New York, said the findings were based on a “very simplified model of cancer mutation” and the numbers “should at best be regarded as ballpark estimates.”

“By using only the lowest risk cancers and assuming that mutation rates are the same for all tissues, the study maximises the risk attributed to environmental factors,” he wrote.

“However, we don’t know how tissues differ in their intrinsic mutation rates.”

Paul Pharaoh, a cancer epidemiology professor at Cambridge University, pointed out there were different levels of internal and external risk for different cancer types. The results, he said, “do not tell us anything about the absolute risks of any given cancer. “These findings do not have any implications for cancer treatment, but they do tell us that most cancers would be preventable if we knew all of the extrinsic risk factors that cause disease.”

The Science study had caused much debate for suggesting that “bad-luck” DNA mutations could explain about 75 percent of cases for many types of cancer -- meaning they could not be prevented by a healthy lifestyle.

The World Health Organization’s cancer agency at the time “strongly disagreed” with the study’s findings, which it said could have “serious negative consequences” for cancer

research and healthy behaviour.

Regular testing for ovarian cancer could reduce deaths from this “silent killer” of women by a fifth, researchers said Thursday.

There is no standard or routine test for early detection of ovarian cancer -- a process known as “screening” to boost survival chances by allowing for treatment to begin as soon as possible after disease onset.

The rare but deadly disease, with few early symptoms, is often diagnosed at a very advanced stage, and about 60 percent of patients die within five years.

To test whether screening would be useful, researchers conducted a trial with more than 200,000 women between the ages of 50 and 74 in England, Northern Ireland and Wales. The research team from Britain and Australia divided the women into three groups.

Over an average period of 11.1 years, 50,624 women were given an annual blood test as well as ultra- sound scan, another 50,623 an annual scan only, and 101,299 women received no screening. By the end, 649 of the women in the trial died of ovarian cancer, the team reported in The Lancet medical journal.

Comparing the groups, the researchers calculated a “mortality reduction” ranging from 15-28 percent depending on the number of years of screening.

On average, death was reduced by 20 percent. The researchers calculated that 641 women would need to be screened to prevent one ovarian cancer death over a 14-year period.

“The findings are of importance given the limited progress in treatment outcomes for ovarian cancer over the last 30 years,” said study co-author Usha Menon of University College London.

Screening improves the chances of diagnosing the disease, but there is also the question as to whether it helps the patient, or whether the money spent on investing in testing could be put to other uses.

Federal health officials have cleared a wearable heartzapping device for children who are at risk of deadly irregular heartbeats.

The LifeVest is intended for children who need round-the-clock heart monitoring but cannot receive an implantable device, due to health problems or parental objections. Defibrillators correct dangerous heart rhythms by jolting the heart with an electrical current. Most adults at risk of cardiac arrest have the life-saving devices surgically implanted. External defibrillators are also used in emergencies, but they must be operated by a second person.

LifeVest which includes an electrode belt and a heart monitor is already approved for adults. It is intended for patients who weigh at least 41 pounds.

Food and Drug Administration officials said Thursday’s approval would help doctors safely prescribe the device for children.