Tumor Characteristics Associated With Mammographic Detection of Breast Cancer in the Ontario Breast Screening Program

• Published in: JNCI : Journal of the National Cancer Institute Vol. 103; no. 12; pp. 942 - 950
• Main Authors: Kirsh, Victoria A., Chiarelli, Anna M., Edwards, Sarah A., O'Malley, Frances P., Shumak, Rene S., Yaffe, Martin J., Boyd, Norman F.
• Format: Journal Article
• Language: English
• Published: Cary, NC Oxford University Press 22.06.2011; Oxford Publishing Limited (England)
• Subjects: Aged; Biological and medical sciences; Biomarkers, Tumor - analysis; Breast cancer; Breast Neoplasms - chemistry; Breast Neoplasms - diagnostic imaging; Breast Neoplasms - pathology; Case-Control Studies; Comparative studies; Confounding Factors (Epidemiology); Early Detection of Cancer; Female; Gynecology. Andrology. Obstetrics; Humans; Logistic Models; Mammary gland diseases; Mammography; Mass Screening - methods; Medical prognosis; Medical sciences; Middle Aged; Odds Ratio; Ontario; Predictive Value of Tests; Prognosis; Receptors, Estrogen - analysis; Receptors, Progesterone - analysis; Research Design; Risk Factors; Surveys and Questionnaires; Tumors; Womens health; Canada; North America; Ontario; America; Ontario Canada; Mammary gland diseases; Breast disease; Cancerology; Program; Radiodiagnosis; Breast cancer; Mammography; Malignant tumor; Diagnosis; Medical screening; Cancer
• ISSN: 0027-8874; 1460-2105
• DOI: 10.1093/jnci/djr138

Background Few studies have compared the prognostic value of tumor characteristics by type of breast cancer diagnosed in the interval between mammographic screenings with screen-detected breast cancers. Methods We conducted a case-case study within the cohort of women (n = 431 480) in the Ontario Breast Screening Program who were aged 50 years and older and were screened between January 1, 1994, and December 31, 2002. Interval cancers, defined as breast cancers diagnosed within 24 months after a negative screening mammogram, were designated as true interval cancers (n = 288) or missed interval cancers (n = 87) if they were not identified at the time of screening but were identified in retrospect. Screen-detected breast cancers (n = 450) were selected to match interval cancers. Tumors were evaluated for stage, grade, mitotic index, histology, and expression of hormone receptors and odds ratios (ORs) and 95% confidence intervals (CIs) were calculated by conditional logistic regression. Results Both true and missed interval cancers were of higher stage and grade than matched screen-detected breast cancers. However, true interval cancers had a higher mitotic index (OR = 3.13, 95% CI = 1.81 to 5.42), a higher percentage of nonductal histology (OR = 1.94, 95% CI = 1.05 to 3.59), and were more likely to be both estrogen receptor-negative (OR = 2.09, 95% CI = 1.32 to 3.30) and progesterone receptor-negative (OR = 2.49, 95% CI = 1.68 to 3.70) compared with matched screen-detected tumors. Conclusions In this study, interval cancers were of higher stage and grade compared with screen-detected cancers. True interval cancers were more likely to have additional adverse prognostic features of estrogen and progesterone receptor negativity and nonductal morphology. The findings suggest a need for more sensitive screening modalities to detect true interval breast cancers and different approaches for early detection of fast-growing tumors.