However the recall rate for abnormal mammograms seems to be significantly lower in Norway. There is also a difference in the process involved in breast cancerdefine screening in the two countries itself.
In the United States, breast cancer screening is generally done in response to a physician's recommendation, which is known as "opportunistic screening". US women are advised to have screening mammograms annually.
The breast cancer screening programs in Norway and in some other European countries involve sending out letters to women of a specific age group inviting them for screening mammograms. The program seeks to have women screened for breast cancer every two years.
The difference in the two approaches also is a major factor in the complications that arise when there is talk of any effective comparisons. As such, few studies have been initiated to break this ground so far.
The study was conducted by Berta Geller of the University of Vermont in Burlington; Solveig Hofvind, Ph.D., of the Cancer Registry of Norway; and other team members. The team studied over 45,050 women in Vermont and 194,430 women in Norway during the period 1997 to 2003. The women were aged 50 to 69 years at the time of screening.
The researchers compared the screening approaches of the two countries along parameters like the percentage of women recalled for a re-evaluation, the screening detection rate of breast cancer, and the rate of interval cancers.
The screening detection rate of cancers was found to be similar in the two populations (2.77 per 1,000 woman-years in Vermont versus 2.57 in Norway).
More than three times as many women were recalled for further examination following abnormal mammograms in Vermont than in Norway (9.8 percent versus 2.7 percent, respectively).
The rate of interval cancers was shown to be higher in Vermont than in Norway (1.24 per 1,000 woman-years versus 0.86), and 55.9 percent of the interval cancers was lower in Vermont compared to the 38.2 percent observed in Norway.
When all results for all cancers detected during regular screening and between screening mammograms were compared, no substantial differences in the prognostic features of the cancers could be pin-pointed in the two strands of population.
This is what the authors of the study had to say, “Our results demonstrate that despite its longer screening interval, the organized population-based screening program in Norway achieved similar outcomes as the opportunistic screening in Vermont.”
The researchers were surprised to find a higher interval cancer rate in the US women. Their hypothesis is that "Vermont women and/or their health care providers may more readily pursue evaluation of symptoms and clinical findings than their Norwegian counterparts."
The report was published in the July 29 online issue of the Journal of the National Cancer Institute.
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