Table 2. Multivariable analyses assessing impact of demographic, treatment/treatment center, and prognostic factors on TTI.
| Category | Predicted TTI | RR (95% CI) | P value |
|---|---|---|---|
| Race/ethnicity | |||
| Non-Hispanic White | 37.8 | Reference | |
| Hispanic | 48.0 | 1.19 (1.14–1.24) | <0.001 |
| Non-Hispanic Black | 49.5 | 1.21 (1.17–1.25) | <0.001 |
| AAPI | 42.1 | 1.06 (0.97–1.17) | 0.182 |
| Other/unknown | 36.5 | 0.97 (0.94–1.01) | 0.197 |
| Gender | |||
| Male | 42.8 | Reference | |
| Female | 37.7 | 0.92 (0.90–0.94) | <0.001 |
| Year of diagnosis | |||
| 2004 | 34.8 | Reference | |
| 2005 | 37.1 | 1.06 (1.00–1.12) | 0.050 |
| 2006 | 36.2 | 1.04 (0.99–1.10) | 0.141 |
| 2007 | 38.7 | 1.09 (1.04–1.15) | 0.001 |
| 2008 | 38.3 | 1.08 (1.03–1.14) | 0.002 |
| 2009 | 38.6 | 1.07 (1.01–1.12) | 0.011 |
| 2010 | 40.0 | 1.10 (1.05–1.16) | <0.001 |
| 2011 | 40.2 | 1.09 (1.04–1.15) | <0.001 |
| 2012 | 39.0 | 1.06 (1.01–1.11) | 0.027 |
| 2013 | 40.7 | 1.11 (1.05–1.16) | <0.001 |
| 2014 | 41.4 | 1.13 (1.08–1.19) | <0.001 |
| Age (years) | |||
| >70 | 38.6 | Reference | |
| 61–70 | 39.1 | 0.89 (0.79–1.01) | 0.061 |
| 51–60 | 39.0 | 0.99 (0.96–1.02) | 0.534 |
| 41–50 | 39.6 | 1.00 (0.97–1.03) | 0.797 |
| ≤40 | 43.3 | 1.00 (0.97–1.03) | 0.852 |
| Insurance type | |||
| Private insurance | 36.7 | Reference | |
| Medicare | 39.7 | 1.07 (1.05–1.10) | <0.001 |
| Medicaid | 46.3 | 1.17 (1.14–1.21) | <0.001 |
| Not insured | 41.8 | 1.11 (1.07–1.16) | <0.001 |
| Other/unknown | 45.6 | 1.17 (1.11–1.23) | <0.001 |
| Median household income (dollars) in zip code of patient residence | |||
| ≥63,000 | 37.5 | Reference | |
| 48,000–62,999 | 38.7 | 1.02 (0.99–1.04) | 0.222 |
| 38,000–47,999 | 39.8 | 1.02 (0.99–1.05) | 0.173 |
| <38,000 | 41.8 | 1.00 (0.96–1.04) | 0.890 |
| Unknown | 39.7 | 0.77 (0.49–1.21) | 0.257 |
| Education status (% without high school diploma) in zip code of patient residence | |||
| <7.0 | 36.3 | Reference | |
| 7.0–12.9 | 38.5 | 1.11 (1.06–1.15) | <0.001 |
| 13–20.9 | 40.0 | 1.06 (1.03–1.09) | <0.001 |
| ≥21.0 | 43.5 | 1.05 (1.02–1.08) | <0.001 |
| Unknown | 40.1 | 1.64 (0.96–2.81) | 0.069 |
| Urban/rural category | |||
| Metropolitan ≥1 million | 40.9 | Reference | |
| Metropolitan <1 million | 37.0 | 0.95 (0.92–0.97) | <0.001 |
| Urban | 37.8 | 0.92 (0.89–0.95) | <0.001 |
| Rural | 39.0 | 0.93 (0.86–1.00) | 0.052 |
| Unknown | 39.3 | 0.97 (0.91–1.04) | 0.449 |
| Distance to reporting facility (miles) | |||
| ≤10 | 38.9 | Reference | |
| 11–20 | 38.9 | 1.03 (1.00–1.05) | 0.032 |
| 21–50 | 38.9 | 1.02 (0.99–1.05) | 0.123 |
| >50 | 43.6 | 1.11 (1.06–1.15) | <0.001 |
| Reporting facility type | |||
| Community | 38.1 | Reference | |
| Comprehensive community | 36.0 | 0.95 (0.92–0.98) | 0.003 |
| Academic | 43.9 | 1.08 (1.04–1.12) | <0.001 |
| Integrated network | 37.8 | 0.94 (0.90–0.99) | 0.011 |
| Unknown | 45.0 | 1.20 (1.05–1.36) | 0.006 |
| Reporting facility anal cancer patient volume | |||
| Lower tertile | 37.9 | Reference | |
| Middle tertile | 37.3 | 0.99 (0.96–1.03) | 0.715 |
| Upper tertile | 39.9 | 1.02 (0.98–1.06) | 0.256 |
| Transitions in care | |||
| No | 37.7 | Reference | |
| Yes | 41.5 | 1.13 (1.11–1.16) | <0.001 |
| Unknown | 35.7 | 1.01 (0.98–1.05) | 0.402 |
| Radiation plan type | |||
| Non-IMRT, non-proton | 37.8 | Reference | |
| IMRT, proton | 41.0 | 1.06 (1.04–1.08) | <0.001 |
| Charlson/Deyo comorbidity score | |||
| 0 | 38.7 | Reference | |
| 1 | 39.2 | 1.01 (0.98–1.04) | 0.560 |
| 2 | 45.9 | 1.09 (1.05–1.13) | <0.001 |
| Clinical tumor classification | |||
| T1 | 43.1 | Reference | |
| T2 | 38.5 | 0.88 (0.86–0.90) | <0.001 |
| T3 | 37.6 | 0.84 (0.82–0.87) | <0.001 |
| T4 | 40.4 | 0.91 (0.87–0.94) | <0.001 |
| T0/IS | 37.9 | 0.85 (0.61–1.18) | 0.323 |
| Unknown | 44.5 | 0.99 (0.91–1.06) | 0.695 |
| Clinical nodal classification | |||
| N0 | 39.0 | Reference | |
| N1 | 37.8 | 0.97 (0.94–1.00) | 0.032 |
| N2 | 39.8 | 1.00 (0.98–1.03) | 0.720 |
| N3 | 41.6 | 1.01 (0.98–1.04) | 0.494 |
| Unknown | 38.5 | 0.99 (0.92–1.07) | 0.877 |
P values reported from Wald test of zero-inflated Negative Binomial regression model. TTI, time to treatment initiation; RR, relative risk; CI, confidence interval; AAPI, Asian-American and Pacific Islander; IMRT, intensity-modulated radiation therapy; IS, in situ.