Vitamin D intake, month the mammogram was taken and mammographic density in Norwegian women aged 50-69.

BACKGROUND: The role of vitamin D in breast cancer etiology is unclear. There is some, but inconsistent, evidence that vitamin D is associated with both breast cancer risk and mammographic density (MD). We evaluated the associations of MD with month the mammogram was taken, and with vitamin D intake, in a population of women from Norway--a country with limited sunlight exposure for a large part of the year. METHODS: 3114 women aged 50-69, who participated in the Norwegian Breast Cancer Screening Program (NBCSP) in 2004 or 2006/07, completed risk factor and food frequency (FFQ) questionnaires. Dietary and total (dietary plus supplements) vitamin D, calcium and energy intakes were estimated by the FFQ. Month when the mammogram was taken was recorded on the mammogram. Percent MD was assessed using a computer assisted method (Madena, University of Southern California) after digitization of the films. Linear regression models were used to investigate percent MD associations with month the mammogram was taken, and vitamin D and calcium intakes, adjusting for age, body mass index (BMI), study year, estrogen and progestin therapy (EPT), education, parity, calcium intakes and energy intakes. RESULTS: There was no statistical significant association between the month the mammogram was taken and percent MD. Overall, there was no association between percent MD and quartiles of total or dietary vitamin D intakes, or of calcium intake. However, analysis restricted to women aged <55 years revealed a suggestive inverse association between total vitamin D intake and percent MD (p for trend = 0.03). CONCLUSION: Overall, we found no strong evidence that month the mammogram was taken was associated with percent MD. We found no inverse association between vitamin D intake and percent MD overall, but observed a suggestive inverse association between dietary vitamin D and MD for women less than 55 years old.

Variation in detection of ductal carcinoma in situ during screening mammography: a survey within the International Cancer Screening Network.

BACKGROUND: There is concern about detection of ductal carcinoma in situ (DCIS) in screening mammography. DCIS accounts for a substantial proportion of screen-detected lesions but its effect on breast cancer mortality is debated. The International Cancer Screening Network conducted a comparative analysis to determine variation in DCIS detection. PATIENTS AND METHODS: Data were collected during 2004-2008 on number of screening examinations, detected breast cancers, DCIS cases and Globocan 2008 breast cancer incidence rates derived from national or regional cancer registers. We calculated screen-detection rates for breast cancers and DCIS. RESULTS: Data were obtained from 15 screening settings in 12 countries; 7,176,050 screening examinations; 29,605 breast cancers and 5324 DCIS cases. The ratio between highest and lowest breast cancer incidence was 2.88 (95% confidence interval (CI) 2.76-3.00); 2.97 (95% CI 2.51-3.51) for detection of breast cancer; and 3.49 (95% CI 2.70-4.51) for detection of DCIS. CONCLUSIONS: Considerable international variation was found in DCIS detection. This variation could not be fully explained by variation in incidence nor in breast cancer detection rates. It suggests the potential for wide discrepancies in management of DCIS resulting in overtreatment of indolent DCIS or undertreatment of potentially curable disease. Comprehensive cancer registration is needed to monitor DCIS detection. Efforts to understand discrepancies and standardise management may improve care.

Asymptomatic breast cancer in non-participants of the national screening programme in Norway: a confounding factor in evaluation?

OBJECTIVE: To evaluate the extent and histopathological characteristics of asymptomatic breast cancer detected outside the Norwegian Breast Cancer Screening Program (NBCSP) in women targeted by the programme. METHODS: Our study included 568 primary breast cancers (523 invasive and 45 ductal carcinoma in situ) diagnosed in 553 women aged 50-70, residing in Møre og Romsdal County, 2002-2008. The cancers were divided into screening-detected cancers in the NBCSP, interval cancers (ICs) and cancers detected in women not participating in the NBCSP (never participated and lapsed attendees), and further into asymptomatic and symptomatic cancers. Nottingham Prognostic Index (NPI) was used for comparisons across the groups and the distributions were compared using chi-square tests for statistical significance. RESULTS: Twenty percent (19/97) of the ICs and 32% (69/213) of the breast cancers in non-participants were asymptomatic, with opportunistic screening as the most frequent detection method (42%, 8/19 for ICs and 54%, 37/69 for non-participants). There were no differences in distribution of NPI prognostic categories across subgroups of asymptomatic invasive cancers (screening-detected cancers in the NBCSP, asymptomatic ICs and asymptomatic cancers in non-participants) or between subgroups of symptomatic invasive cancers (symptomatic ICs and symptomatic cancers in non-participants). Asymptomatic cancers had a significantly more favourable distribution of NPI prognostic categories compared with symptomatic cancers (P < 0.001). The proportion of invasive cancers with excellent/good NPI was 53% (164/310) for all asymptomatic and 25% (52/211) for all symptomatic invasive cancers. CONCLUSIONS: A considerable percentage of breast cancers detected outside the organized screening programme were asymptomatic, with a prognostic profile comparable with screening-detected breast cancers in the NBCSP. Individual data regarding the detection method for all breast cancers are needed for a complete evaluation of the organized screening programme in Norway.