Table 2.

Breast Cancer Incidence Rates by CAD Use^*

Breast Cancer Diagnosis Within 1 y	Non-CAD†		CAD‡		Unadjusted IRR (95% CI)	Adjusted OR§ (95% CI)	P Value§
	Breast Cancer Cases n	Incidence Rate║	Breast Cancer Cases n	Incidence Rate║
Any breast cancer	31 339	8.21	15 022	8.16	0.99 (0.97–1.01)	1.04 (1.01–1.06)	0.009
Invasive breast cancer¶	24 804	6.50	11 466	6.23	0.95 (0.93–0.98)	1.00 (0.97–1.03)	0.98
Stage I invasive	14 875	3.90	7335	3.98	1.02 (0.99–1.05)	1.06 (1.03–1.10)	<0.001
Stages II–IV invasive	8186	2.15	3441	1.87	0.87 (0.83–0.91)	0.92 (0.87–0.96)	<0.001
DCIS	6535	1.71	3556	1.93	1.13 (1.08–1.18)	1.17 (1.11–1.23)	<0.001

CAD = computer-aided detection; DCIS = ductal carcinoma in situ; IRR = incidence rate ratio; OR = odds ratio.

^*Mammograms for women without breast cancer (from the SEER [Surveillance, Epidemiology and End Results]–Medicare 5% noncancer sample) are probability-weighted by a factor of 20 so that the analysis represents the entire population of fee-for-service Medicare enrollees having screening mammography (weighted: 5 656 860 screening mammograms, including 46 361 done within 1 y of breast cancer diagnosis).

^†284 501 woman-years of follow-up, unweighted.

^‡124 958 woman-years of follow-up, unweighted.

^§Adjusted for age, race or ethnicity, rural vs. urban residence, median income of elderly residents within the same ZIP code, time since previous mammogram, use of CAD on the previous examination, presence of stable and unstable comorbid conditions, digital vs. film mammography, year of examination, and SEER region. Because breast cancer is uncommon, the adjusted OR closely approximates the adjusted incidence rate ratio. Owing to missing covariate or outcome data, 35 531 mammograms (8.7% of total) from 13 136 women (8.3% of total) were excluded from adjusted analyses (unweighted: 373 928 mammograms from 144 022 women).

^║Incidence per 1000 women-years.

^¶Incidence rates for overall invasive cancer include both staged and unstaged cancer.