57% Decline in Rhode Island Invasive Breast Cancer Mortality Between 1987 and 2017: Mammography Predominates in Preventing Mortality
Blake Cady, John Fulton
Rhode Island Cancer Registry, Department of Public Health, Providence, RI
BACKGROUND: Controversy exists regarding proportional contributions of mammographic screening versus systemic therapy to declining disease-specific mortality of female invasive breast cancer in the U.S. Understanding these relative contributions may help address allocation of medical resources.
METHODS: A 31-year (1987-2017) review of Rhode Island Cancer Registry data of female invasive breast cancer was carried out in a state with a high rate of mammographic screening.
RESULTS: Over 31 years in RI, statistically significant improvements occurred in initial clinical presentation of invasive breast cancer: mean and median maximum cancer diameter decreased by 21% and 30% respectively. Despite 1997 introduction of more accurate sentinel lymph node biopsy, the proportion of patients with axillary lymph node metastases decreased by 27%; extent of nodal metastases also decreased; patients with over 3 node metastases decreased 67%.
By 2017, 53% of all patients with node metastases had only one. Poorly differentiated cancers decreased 50%. Disease-specific mortality decreased 57%.
CONCLUSIONS: Improvements in initial presentation of invasive breast cancers are consistent with most cases having progressive growth, from cellular origin to palpable mass, the currently accepted biological model. Breast cancers identified earlier in clinical presentation through screening mammography are characterized by smaller size, fewer axillary lymph node metastases, better grade differentiation, and decreased mortality. Extrapolation from improved clinical parameters at diagnosis indicate that majority of mortality decline of invasive breast cancer in RI can be attributed to earlier detection.
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