Table 3.

Multivariable cox regression analyses.

	Netherlands		Taiwan		Combined
	HR	95% CI	HR	95% CI	HR	95% CI
Country
Taiwan	–	–	–	–	1.00	–
The Netherlands	–	–	–	–	1.06	1.01–1.12
Age
< 60 years	1.00	–	1.00	–	1.00	–
60–69 years	1.49	1.36–1.62	1.29	1.23–1.35	1.31	1.26–1.36
≥ 70 years	2.80	2.58–3.04	2.30	2.18–2.43	2.40	2.30–2.50
Gender
Female	1.00	–	1.00	–	1.00	–
Male	1.27	1.19–1.36	1.23	1.15–1.32	1.23	1.18–1.29
Period of diagnosis
2004–2007	1.00	–	1.00	–	1.00	–
2008–2011	0.93	0.86–1.01	0.82	0.78–0.86	0.85	0.82–0.88
2012–2016	0.87	0.80–0.96	0.67	0.64–0.70	0.73	0.70–0.76
Stage
Early stage	1.00	–	1.00	–	1.00	–
Advanced stage	1.93	1.78–2.10	2.29	2.18–2.41	2.19	2.10–2.29
Unknown	1.46	0.93–2.31	1.57	1.35–1.83	1.46	1.26–1.69
Location
Other/unspecified parts of tongue	1.00	–	1.00	–	1.00	–
Mucosa of lip	0.76	0.56–1.02	1.13	0.99–1.28	1.06	0.94–1.19
Floor of mouth and gum	1.11	1.03–1.20	0.98	0.92–1.03	1.01	0.97–1.06
Hard palate	0.92	0.70–1.22	1.40	1.25–1.57	1.30	1.17–1.45
Buccal and other parts of mouth	1.02	0.92–1.13	1.01	0.97–1.05	1.00	0.96–1.04
Grade
Well differentiated	1.00	–	1.00	–	1.00	–
Moderately differentiated	1.51	1.35–1.68	1.36	1.31–1.42	1.38	1.33–1.44
Poorly or undifferentiated	1.90	1.67–2.15	2.06	1.93–2.20	1.92	1.82–2.03
Unknown	1.50	1.33–1.70	1.10	1.02–1.19	1.24	1.17–1.32
Treatment
Primary surgery	1.00	–	1.00	–	1.00	–
Surgery and radiotherapy and/or chemotherapy	1.04	0.96–1.13	1.52	1.45–1.60	1.40	1.34–1.46
Hospital volume (oral cavity surgeries/year)
≥ 100	1.00	–	1.00	–	1.00	–
50–99	0.90	0.79–1.03	1.00	0.95–1.04	1.01	0.97–1.05
< 50	0.94	0.82–1.07	1.19	1.13–1.25	1.13	1.08–1.18

The figures in the Netherlands and Taiwan columns are computed locally, while the Combined column was computed using the privacy-preserving federated algorithm.