Weedon-Fekjær et al [1] write in their abstract “The incidence of invasive breast cancer in Norway increased steadily until 2002, levelled off, and then declined from 2006”. This is simply not true.

The incidence rate of breast cancer was 178 per 100 000 women in 1991 (for the age group 40-79 year). Then it suddenly increased from 183 (in 1995) to 210 in 1996 when screening started. It peaked in the period 2002-2005 (231, 233, 232 and 230 per 100 000 women). All increase was in the age group 50-69 years who were invited to screening [2,3,4]. In 2006 it was 219.6 and in 2009 it was 217.1 [5]. The decline after the peak was only observable in counties that had done a prevalence screening [3,4]. Incidence rates always drop after a prevalence screening and this decline cannot be attributed to hormones. The decline after 2006 is 1.2% and is not significant.

After year 2002 the sale figures of hormone replacement therapy have dropped 70% while there has not been any drop in breast cancer rates that cannot be explained by the prevalence peak in the screening program [3,4]. You do not need age-period-cohort models to understand that hormone replacement therapy cannot be important for understanding the trends in the incidence rates in Norway. If Weedon-Fekjær et al. [1] had published any raw data in their paper, the flaws in this paper would have been evident. Thank God that we have raw data available on internet [5]. And thank BMJ for their system of rapid responses so obvious flaws can be corrected.

1. Weedon-Fekjær, H, bakken K, Vatten LJ, Tretli S. Understanding recent trends in incidence of invasive breast cancer in Norway: age-period-cohort analysis based on registry data on mammography screening and hormone treatment use. BMJ 2012; 344: e299.
2. Zahl P-H, Strand BH, Mæhlen J. Breast cancer incidence in Norway and Sweden during introduction of nation-wide screening: prospective cohort study. BMJ 2004; 328: 921-4.
3. Suhrke Suhrke P, Mæhlen J, Zahl P-H. Hormone therapy use and breast cancer incidence by histological subtypes in Sweden and Norway. The Breast Journal 2011 (in press).
4. Zahl P-H, Mæhlen J. Overdiagnosis of breast cancer after 14 year with mammography screening. Tidsskr Nor Lægeforen 2012 (in press).
5. http://www-dep.iarc.fr/nordcan.htm (accessed February 9th, 2012)

Competing interests: None declared