Table 3. Cox Regression by Cancer Stage at Diagnosis.
| Cancer stage | Postexpansion vs preexpansion, HR (95% CI) | P value | DID HR (95% CI)a | P value |
|---|---|---|---|---|
| I-III (nonmetastatic) | ||||
| Nonexpansion states | 1.05 (1.02-1.08) | <.001 | 1 [Reference] | NA |
| Combined expansion states | 0.99 (0.97-1.02) | .64 | 1.05 (1.02-1.09)b | .003 |
| IV (metastatic) | ||||
| Nonexpansion states | 0.97 (0.95-0.99) | .003 | 1 [Reference] | NA |
| Combined expansion states | 0.99 (0.98-1.01) | .52 | 0.98 (0.95-1.00)b | .08 |
Abbreviations: DID, difference-in-difference; HR, hazard ratio; NA, not applicable.
a
Refers to ratio of preexpansion to postexpansion HR in nonexpansion states compared with preexpansion to postexpansion HR in combined expansion states. Ratios greater than 1 indicate more improvement in expansion states than in nonexpansion states.
b
A 3-way interaction term indicates that the mortality benefit among patients with stages I to III in combined expansion states compared with nonexpansion states is significantly different from the mortality among patients with stage IV cancer in nonexpansion states compared with combined expansion states (DID HR, 1.05 [95% CI, 1.02-1.09] vs 0.98 [95% CI, 0.95-1.00]; P = .002).