Table 3. Multivariable proportional hazard model without propensity score adjustment (N = 7,288).
Covariate | Level | HR | 95 % CI Low | 95 % CI High | HR p value |
---|---|---|---|---|---|
Age at diagnosis | ≤50 y | 0.689 | 0.632 | 0.751 | <0.001 |
50–65 y | 0.791 | 0.731 | 0.857 | <0.001 | |
65–75 y | 0.886 | 0.821 | 0.955 | 0.002 | |
>75 y | – | – | – | – | |
Median income, 2000 | <$30,000 | 1.170 | 1.077 | 1.272 | <0.001 |
$30,000-$34,999 | 1.089 | 1.010 | 1.174 | 0.027 | |
$35,000-$45,999 | 1.025 | 0.963 | 1.092 | 0.441 | |
>$46,000 | – | – | – | – | |
Year of diagnosis | 1998 | 1.078 | 0.993 | 1.171 | 0.073 |
1999 | 1.026 | 0.947 | 1.112 | 0.524 | |
2000 | 1.020 | 0.942 | 1.104 | 0.628 | |
2001 | 0.935 | 0.867 | 1.009 | 0.085 | |
2002 | – | – | – | – | |
Facility volume (unit = 50) | 0.962 | 0.941 | 0.983 | <0.001 | |
Facility typea | CCP | 1.104 | 1.002 | 1.217 | 0.047 |
CCCP | 1.064 | 1.002 | 1.131 | 0.044 | |
ARCP | – | – | – | – | |
Primary site | Head | 1.160 | 0.958 | 1.405 | 0.128 |
Body | 1.172 | 0.938 | 1.465 | 0.162 | |
Tail | 0.930 | 0.751 | 1.151 | 0.505 | |
Body/tail | – | – | – | – | |
Tumor size | ≤25 mm | 0.733 | 0.677 | 0.794 | <0.001 |
25–35 mm | 0.884 | 0.815 | 0.959 | 0.003 | |
35–45 mm | 0.942 | 0.863 | 1.029 | 0.187 | |
>45 mm | – | – | – | – | |
Stage | I | 0.592 | 0.520 | 0.674 | <0.001 |
II | 0.809 | 0.715 | 0.916 | <0.001 | |
III | 0.806 | 0.732 | 0.886 | <0.001 | |
IV | – | – | – | – | |
Grade | Unspecified | 0.441 | 0.395 | 0.492 | <0.001 |
I | 0.455 | 0.413 | 0.501 | <0.001 | |
II | 0.768 | 0.725 | 0.813 | <0.001 | |
III/IV | – | – | – | – | |
Surgical margin positive | No | 0.709 | 0.668 | 0.753 | <0.001 |
Yes | – | – | – | – | |
LN positive | No | 0.724 | 0.641 | 0.818 | <0.001 |
Yes | – | – | – | – | |
No. of examined LNs > 12 | No | 1.109 | 1.046 | 1.175 | <0.001 |
Yes | – | – | – | – | |
Adjuvant therapy | ChemoRad | 0.784 | 0.739 | 0.831 | <0.001 |
ChemoOnly | 1.076 | 0.977 | 1.186 | 0.139 | |
No adjuvant therapy | – | – | – | – |
The model was built by backward elimination with a staying p value of <0.05. The starting list contains all variables that demonstrated significance at the 0.05 level in <T2>Table 2
HR hazard ratio, CI confidence interval, LN lymph node, ChemoOnly chemotherapy only, ChemoRad adjuvant chemoradiotherapy
CCP Community Cancer Program, CCCP Comprehensive Community Cancer Programs, ARCP Academic/Research Cancer Program, all as defined by the Commission on Cancer