FRIDAY, July 29 (HealthDay News) -- Developed countries have seen a drop in breast cancer death rates in recent years, but a new international study suggests this trend is less about rising screening rates and more about the availability of increasingly effective treatments and improving health-care systems.

The finding stems from an analysis of World Health Organization (WHO) breast cancer data collected between 1980 and 2006, in which French, British and Norwegian researchers compared the screening and fatality rates of several Western European countries. The observations were presented online July 29 in the British Medical Journal.

"The contrast between the time differences in implementation of mammography screening and the similarity in reductions in mortality between the country pairs suggest that screening did not play a direct part in the reductions in breast cancer mortality," a team of researchers led by Philippe Autier, research director of the International Prevention Research Institute in Lyon, France, said in a journal news release.

To explore to what degree breast cancer screening rates appeared to be related to fatality rates, the authors chose six countries for points of comparison.

Northern Ireland was stacked up against the Republic of Ireland; the Netherlands was compared with Belgium/Flanders; and Sweden was examined alongside Norway.

The team noted that medical services and the prevalence of breast cancer death risk factors were comparable in each pairing. However, in the space of the study, the second country of each of the three groups was 10 to 15 years behind the first country in terms of their implementation of mammography screening protocols.

The results: Breast cancer death rates, which dropped across the board, were more or less similar in each country pairing, despite stark differences in screening histories.

For example, fatalities between 1989 and 2006 had plummeted by 29 percent in Northern Ireland, as compared with 26 percent in the Republic of Ireland.

The Netherlands registered a 25 percent drop, compared with a 20 percent to 25 percent drop in Belgium/Flanders, while the downward trend of 16 percent in Sweden compared with 24 percent in Norway.

In general terms, Autier's team also noted breast cancer death rates were not that different among women who had undergone almost no screening as compared with those who had been screened quite often.

And the biggest death rate drop seen overall was among women between the ages of 40 and 49, whether or not they had undergone screening.

Dr. Lauren Cassell, chief of breast surgery at Lenox Hill Hospital (affiliated with Northshore/LIJ) in New York City, cautioned that it's not clear that the current findings are easily generalizable to other nations.

"I'm not sure how well this finding would translate in comparison with the U.S.," she noted. "I suspect that we may be more aggressive in our screening protocols, and our health system is very different from the ones they looked at."

"And, in any case, I would certainly say that people should continue getting screened," Cassell stressed. "Because we still do know that catching any cancer at an earlier stage does translate into better outcomes and maybe less treatment. Because even if the end result is the same, and fatal, I certainly would like to have a cancer that could be treated with hormonal treatment and not chemotherapy, if possible."

More information

For more on breast cancer screening guidelines in the United States, visit the American Cancer Society.