THURSDAY, July 31 (HealthDay News) -- Although the organized, population-based screening program in Norway has a longer screening interval, opportunistic mammography screening in Vermont achieves similar outcomes, according to a report published online July 29 in the Journal of the National Cancer Institute.
Solveig Hofvind, Ph.D., of the Cancer Registry of Norway in Oslo, Norway, and colleagues examined differences in breast cancer screening and outcomes between the United States and Norway. The United States generally has a shorter screening interval and mammograms are interpreted by a single reader compared to independent double reading in Norway. The investigators determined recall rates, screen detection, interval cancer rates and prognostic tumor characteristics for 45,050 Vermont women and 194,430 Norwegian women aged 50 to 69 years undergoing mammography between 1997 and 2003.
The age adjusted recall rate was significantly higher in Vermont (9.8 versus 2.7 percent), but there was no significant difference in the age-adjusted screen detection rate per 1,000 woman-years after two years of follow-up (2.77 in Vermont versus 2.57 in Norway), the investigators found. Interval cancer rates per 1,000 woman-years were significantly higher in Vermont compared to Norway (1.24 versus 0.86), but a higher percentage of invasive interval cancers in Vermont compared to Norway were 15 mm or smaller (55.9 versus 38.2 percent) and did not involve the lymph nodes (67.5 versus 57 percent). No differences in prognostic factors of the cancers were noted, the researchers report.
"Screening mammography detected cancer at about the same rate and at the same prognostic stage in Norway and Vermont, with a statistically significantly lower recall rate in Norway," the authors write. "The interval cancer rate was higher in Vermont than in Norway, but tumors that were diagnosed in the Vermont women tended to be at an earlier stage than those diagnosed in the Norwegian women."
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