Table 3.
Ordinal logistic regression analysis to assess the association of the tumour CD274 expression score (predictor) with the density of T cells (outcome)
| Univariable OR (95% CI) | Multivariable OR (95% CI)* | ||
|---|---|---|---|
| Model for CD3+ cell density (n=571, as an ordinal outcome variable) | |||
| Tumour CD274 expression score | 0 | 1 (reference) | 1 (reference) |
| 1 | 0.77 (0.45–1.33) | 0.78 (0.45–1.35) | |
| 2 | 1.34 (0.77–2.32) | 1.37 (0.79–2.38) | |
| 3 | 0.90 (0.53–1.54) | 0.94 (0.55–1.61) | |
| 4 | 1.05 (0.50–2.23) | 1.07 (0.51–2.26) | |
| Ptrend† | 0.60 | 0.51 | |
| Model for CD8+ cell density (n=564, as an ordinal outcome variable) | |||
| Tumour CD274 expression score | 0 | 1 (reference) | 1 (reference) |
| 1 | 0.83 (0.48–1.45) | 0.88 (0.50–1.53) | |
| 2 | 1.30 (0.74–2.27) | 1.49 (0.84–2.62) | |
| 3 | 1.10 (0.64–1.90) | 1.16 (0.67–2.03) | |
| 4 | 1.32 (0.61–2.84) | 1.61 (0.74–3.50) | |
| Ptrend† | 0.16 | 0.08 | |
| Model for CD45RO+ cell density (n=577, as an ordinal outcome variable) | |||
| Tumour CD274 expression score | 0 | 1 (reference) | 1 (reference) |
| 1 | 1.20 (0.70–2.08) | 1.42 (0.81–2.48) | |
| 2 | 1.68 (0.97–2.92) | 2.09 (1.19–3.69) | |
| 3 | 1.69 (0.99–2.90) | 2.06 (1.18–3.59) | |
| 4 | 1.72 (0.81–3.67) | 1.92 (0.89–4.15) | |
| Ptrend† | 0.020 | 0.007 | |
| Model for FOXP3+ cell density (n=549, as an ordinal outcome variable) | |||
| Tumour CD274 expression score | 0 | 1 (reference) | 1 (reference) |
| 1 | 0.46 (0.26–0.82) | 0.46 (0.26–0.82) | |
| 2 | 0.44 (0.25–0.77) | 0.39 (0.22–0.70) | |
| 3 | 0.33 (0.19–0.58) | 0.36 (0.21–0.63) | |
| 4 | 0.21 (0.10–0.45) | 0.22 (0.10–0.47) | |
| Ptrend† | <0.0001 | 0.0002 | |
Abbreviations: CI, confidence interval; OR, odds ratio.
The multivariable ordinal logistic regression analysis model initially included age, sex, year of diagnosis, family history of colorectal carcinoma in any parent or sibling, tumour location, microsatellite instability, CpG island methylator phenotype, KRAS, BRAF, and PIK3CA mutations, and LINE-1 methylation level. A backward elimination with a threshold of P=0.05 was used to select variables in the final models.
Ptrend value was calculated by the linear trend across the ordinal categories of the tumour CD274 expression score (0 to 4, as an ordinal predictor variable) in the ordinal logistic regression model for the density of CD3+ cells, CD8+ cells, CD45RO+ cells, or FOXP3+ cells (an ordinal quartile outcome variable). Because we assessed eight primary outcome variables, we adjusted two-sided α level to 0.006 (=0.05/8) by simple Bonferroni correction.