Stage of breast cancer diagnosis among medically underserved women in California receiving mammography through a state screening program

Objective: This study describes breast cancer stage at diagnosis among California women receiving mammograms through a state-administered screening program in comparison to other California women. Method: Linked data from California-administered screening programs and the California Cancer Registry were used to identify participants diagnosed with breast cancer between 1994 and 2000. Logistic regression was used to compare the adjusted likelihood of late stage disease among program participants (categorized into four subgroups based on the timing and frequency of mammograms) to non-participants in California diagnosed during the same time period. Results: Program participants were significantly more likely than non-participants to be diagnosed at late stage (adjusted OR 1.2; 95% CI 1.1, 1.3), with the highest risk occurring among those diagnosed 0-1 months after initial mammogram (adjusted OR 1.8; 95% CI 1.6, 2.1). The stage distribution among regularly screened participants was similar to non-participants (adjusted OR of late stage disease 0.9; 95% CI 0.7, 1.1). Conclusions: Although program participants were more likely to be diagnosed at late stage than non-participants, their stage distribution was distinctly different according to their pattern of mammography utilization. This likely reflects differential utilization of program diagnostic and screening services, which should be taken into account in program evaluation.