Table 3

Multivariate Cox regression analysis of variables affecting overall survival for patients younger than 50 years with colorectal cancer

Variable	Category	Hazard ratio (95% CI)	p value
Sex	Female	Ref.
Sex	Male	1.21 (1.00–1.45)	0.0485
Diagnosis year	Continuous	0.96 (0.92–1.00)	0.0421
Charlson Comorbidity Index	0	Ref.	< 0.0001
	1	1.04 (0.74–1.46)	0.813
	2	1.55 (1.27–1.90)	< 0.0001
AJCC stage	0 or I	Ref.	< 0.0001
	II	1.73 (0.83–3.61)	0.1437
	III	3.09 (1.46–6.52)	0.0031
	IV	12.31 (6.19–24.48)	< 0.0001
	Unknown	5.66 (2.91–11.01)	< 0.0001
Tumour grade	1	Ref.	< 0.0001
	2	2.28 (1.31–4.00)	0.0039
	3	4.43 (2.41–8.15)	< 0.0001
	Unknown	3.18 (1.79–5.64)	< 0.0001
Tumour location	Colon	Ref.	0.9975
	Sigmoid	1.01 (0.73–1.39)	0.9696
	Rectum	1.01 (0.78–1.31)	0.9448
Surgery	No	Ref.
Surgery	Yes	0.23 (0.18–0.29)	< 0.0001
Chemotherapy	No	Ref.
Chemotherapy	Yes	0.96 (0.75–1.22)	0.7268
Radiation therapy	No	Ref.
Radiation therapy	Yes	0.76 (0.57–1.01)	0.0595
Health care facility type	Academic	Ref.
Health care facility type	Community	1.38 (1.13–1.69)	0.0017
Mean neighbourhood income	< $46 000/yr	Ref.
Mean neighbourhood income	≥ $46 000/yr	1.13 (0.92–1.40)	0.2488
Mean neighbourhood education^*	< 80%	Ref.
Mean neighbourhood education^*	≥ 80%	0.85 (0.69–1.05)	0.1298

AJCC = American Joint Committee on Cancer; CI = confidence interval; Ref. = reference.
↵* 80% of community has highschool degree or higher. This represents the median value across the entire community in the province based on Census data.