Table 4.
Adjusted associations between AI vs tamoxifen initiation among hormone receptor positive breast cancer patients age 55+ years at diagnosis (2001-2016) within 12 months of breast cancer diagnosisa
| Characteristic | AIs first vs. Tamoxifen first | |
|---|---|---|
| Model 1b RR (95% CI) |
Model 2c RR (95% CI) |
|
| Total number of patients | 2746 vs 1592 | 2746 vs 1592 |
| Age at diagnosis | ||
| <45 | -- | -- |
| 45-<55 | -- | -- |
| 55-<65 | 1.00 (Ref) | 1.00 (Ref) |
| 65-<75 | 0.95 (0.91-0.99) | 0.97 (0.93-1.01) |
| ≥75 | 0.85 (0.80-0.90) | 0.88 (0.82-0.94) |
| Year of diagnosis | ||
| 2001-2004 | 0.28 (0.25-0.32) | 0.28 (0.25-0.31) |
| 2005-2008 | 0.74 (0.69-0.78) | 0.73 (0.69-0.78) |
| 2009-2012 | 0.97 (0.93-1.01) | 0.97 (0.93-1.01) |
| 2013-2016 | 1.00 (Ref) | 1.00 (Ref) |
| Race | ||
| White | 1.00 (Ref) | 1.00 (Ref) |
| Black | 1.06 (0.94-1.19) | 1.06 (0.94-1.19) |
| American Indian/Alaska Native | 0.90 (0.67-1.20) | 0.89 (0.66-1.20) |
| Asian/Pacific Islander | 0.91 (0.82-1.01) | 0.91 (0.82-1.01) |
| Other | 1.10 (0.88-1.38) | 1.11 (0.89-1.39) |
| Missing | 1.01 (0.75-1.36) | 1.01 (0.75-1.36) |
| Stage | ||
| I | 0.85 (0.79-0.90) | 0.87 (0.81-0.94) |
| II | 0.90 (0.84-0.95) | 0.90 (0.84-0.97) |
| III | 1.00 (Ref) | 1.00 (Ref) |
| Histology | ||
| Ductal | 1.00 (Ref) | 1.00 (Ref) |
| Lobular | 1.02 (0.96-1.09) | 1.03 (0.96-1.09) |
| Mixed | 1.08 (1.01-1.16) | 1.09 (1.01-1.17) |
| Other | 0.97 (0.86-1.08) | 0.97 (0.87-1.09) |
| HR Status | ||
| ER+/PR+ | 1.00 (Ref) | 1.00 (Ref) |
| ER+/PR− | 1.04 (0.98-1.10) | 1.03 (0.98-1.09) |
| ER−/PR+ | 0.84 (0.59-1.19) | 0.83 (0.59-1.18) |
| HER2 status | ||
| Positive | 1.03 (0.97-1.11) | 1.02 (0.95-1.09) |
| Negative | 1.00 (Ref) | 1.00 (Ref) |
| Missing | 1.05 (0.99-1.11) | 1.05 (0.99-1.11) |
| Tumor size, cm | ||
| <1 | 1.02 (0.94-1.11) | 1.01 (0.94-1.10) |
| 1-<2 | 1.04 (0.98-1.11) | 1.03 (0.96-1.10) |
| 2-<5 | 1.00 (Ref) | 1.00 (Ref) |
| ≥5 | 1.15 (1.05-1.25) | 1.16 (1.06-1.26) |
| Missing | 0.99 (0.73-1.33) | 0.99 (0.73-1.34) |
| Grade | ||
| Well differentiated | 0.91 (0.87-0.97) | 0.93 (0.88-0.99) |
| Moderately differentiated | 0.92 (0.88-0.97) | 0.94 (0.89-0.98) |
| Poorly differentiated/undifferentiated | 1.00 (Ref) | 1.00 (Ref) |
| Surgical procedure | ||
| BCS | 1.00 (Ref) | 1.00 (Ref) |
| BCS + radiotherapy | 1.04 (0.94-1.14) | 1.04 (0.95-1.15) |
| Mastectomy | 1.00 (0.90-1.10) | 1.00 (0.90-1.10) |
| Chemotherapy | ||
| No | 1.00 (Ref) | 1.00 (Ref) |
| Yes | 1.08 (1.02-1.14) | 1.08 (1.03-1.14) |
Abbreviations: HR - Hormone receptor; ER - Estrogen receptor; PR – Progesterone receptor; HER2 - Human epidermal growth factor receptor 2; BCS - Breast conserving surgery (lumpectomy/partial mastectomy)
Analyses are limited to women ages 55+ who initiated tamoxifen or AIs within 12 months of diagnosis (N=4,338)
Adjusted for age at diagnosis (55-<65, 65-<75, 75+), year of diagnosis (2001-2004, 2005-2008, 2009-2012, 2013-2016), stage (I,II,III), grade (I,II,III,IV), HR status (ER+/PR+, ER+/PR−, ER−/PR+), and study site (KP CO, NW and WA)
Adjusted for variables in model 1 + chemotherapy (yes, no), and surgery type (BCS, BCS + radiotherapy, mastectomy)