Abstract
BackgroundBreast cancer prognosis is strongly associated with tumor size at diagnosis. We aimed to identify factors associated with diagnosis of large (> 2 cm) compared to small tumors, and to examine implications for long-term prognosis.MethodsWe examined 2012 women with invasive breast cancer, of whom 1466 had screen-detected and 546 interval cancers that were incident between 2001 and 2008 in a population-based screening cohort, and followed them to 31 December 2015. Body mass index (BMI) was ascertained after diagnosis at the time of study enrollment during 2009. PD was measured based on the contralateral mammogram within 3 years before diagnosis. We used multiple logistic regression modeling to examine the association between tumor size and body mass index (BMI), mammographic percent density (PD), or hormonal and genetic risk factors. Associations between the identified risk factors and, in turn, the outcomes of local recurrence, distant metastases, and death (153 events in total) in women with breast cancer were examined using Cox regression. Analyses were carried out according to mode of detection.ResultsBMI and PD were the only factors associated with tumor size at diagnosis. For BMI (≥25 vs. < 25 kg/m2), the multiple adjusted odds ratios (OR) were 1.37 (95% CI 1.02–1.83) and 2.12 (95% CI 1.41–3.18), for screen-detected and interval cancers, respectively. For PD (≥20 vs. < 20%), the corresponding ORs were 1.72 (95% CI 1.29–2.30) and 0.60 (95% CI 0.40–0.90). Among women with interval cancers, those with high BMI had worse prognosis than women with low BMI (hazard ratio 1.70; 95% CI 1.04–2.77), but PD was not associated with the hazard rate. Among screen-detected cancers, neither BMI nor PD was associated with the hazard rate.ConclusionsIn conclusion, high BMI was associated with the risk of having a tumor larger than 2 cm at diagnosis. Among women with interval cancer, high BMI was associated with worse prognosis. We believe that women with high BMI should be especially encouraged to attend screening.
Highlights
Breast cancer prognosis is strongly associated with tumor size at diagnosis
Since our long-term goal is to individualize the screening process we focused on risk factors that could be measured before diagnosis
Introducing a term for the time between diagnosis and study entry caused minimal change in the estimated odds ratios (OR) related to high body mass index (BMI); for screen-detected cancers the OR changed from 1.37 to 1.32
Summary
Breast cancer prognosis is strongly associated with tumor size at diagnosis. We aimed to identify factors associated with diagnosis of large (> 2 cm) compared to small tumors, and to examine implications for long-term prognosis. Breast cancer screening has been estimated to reduce breast cancer mortality by around 30%; 23% among those invited and 40% among those attending [1]. Identifying women at risk of being diagnosed with a large tumor may be the best approach to further reduce breast cancer mortality. Breast cancers are detected either through mammographic screening or by clinical symptoms. Among women who regularly attend screening and are diagnosed with breast cancer, about 30% are interval cancers [4], a term used for cancers detected clinically in the time interval after a negative screen and before the planned screen. Patient characteristics hindering mammographic screen detection may well differ from those hindering clinical detection
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