Table 2.
Patterns of drug switching among older women who initiated hormonal therapy with aromatase inhibitors
| Drug-switching measures | Non-LISa |
LISa |
||||||
|---|---|---|---|---|---|---|---|---|
| Pregeneric entry period (n = 4978) No. (%) | Postgeneric entry period (n = 10 951) No. (%) | Difference, percentage point | P b | Pregeneric entry period (n = 1582) No. (%) | Postgeneric entry period (n = 3166) No. (%) | Difference, percentage point | P b | |
| Any switches | 888 (17.8) | 2184 (19.9) | 2.1 | .002 | 198 (12.5) | 542 (17.1) | 4.6 | <.001 |
| Any switches within 1 y | 630 (12.7) | 1637 (14.9) | 2.3 | .007 | 144 (9.1) | 399 (12.6) | 3.5 | <.001 |
| Any switches from TAX to AIa | 58 (1.2) | 151 (1.4) | 0.2 | .53 | 18 (1.1) | 47 (1.5) | 0.3 | .33 |
| Any switches from AI to TAX | 526 (10.6) | 851 (7.8) | −2.8 | <.001 | 93 (5.9) | 196 (6.2) | 0.3 | .67 |
| Any switches from AI to another AI | 437 (8.8) | 1596 (14.6) | 5.8 | <.001 | 116 (7.3) | 396 (12.5) | 5.2 | <.001 |
| Any switches from AI to another AI or from TAX to AIc | 488 (9.8) | 1698 (15.5) | 5.7 | <.001 | 132 (8.3) | 432 (13.6) | 5.3 | <.001 |
Given that all women started with AIs, women who had switches from tamoxifen to AIs must first have switches from an AI to tamoxifen. AI = aromatase inhibitor; LIS = women who received low-income subsidy for all follow-up months; non-LIS = women who did not receive Medicare Part D low-income subsidy for all follow-up months; TAX = tamoxifen.
Two-sided z test.
One woman could have both types of switches (from AI to another AI and from TAX to AI), and thus percentages do not add up.