Table 1 Characteristics of matched study population in the primary analysis
| Â | Â | Surgery | Â | CCRT | Â | Standardized differencea |
|---|---|---|---|---|---|---|
| Â | Â | Number or mean (sd)a | (%)a | Number or mean (sd)a | (%)a | |
Age | Â | 56.93 (8.65) | Â | 57.26 (10.48) | Â | 0.04 |
Gender | Female | 8 | (5) | 7 | (5) | 0.03 |
Male | 141 | (95) | 142 | (95) | Â | |
Residency | Non-north | 101 | (68) | 100 | (67) | 0.01 |
North | 48 | (32) | 49 | (33) | Â | |
Tumor size | ≤ 5 cm | 59 | (40) | 60 | (40) | 0.01 |
> 5 cm | 90 | (60) | 89 | (60) |  | |
Differentiation | Poorly/undifferentiated | 46 | (31) | 53 | (36) | 0.10 |
Well/moderately | 103 | (69) | 96 | (64) | Â | |
RT delivery | Non-IGRT | 131 | (88) | 128 | (86) | 0.06 |
IGRT | 18 | (12) | 21 | (14) | Â | |
Institution | Low volume | 50 | (34) | 54 | (36) | 0.06 |
High volume | 99 | (66) | 95 | (64) | Â | |
Period | 2008–2009 | 18 | (12) | 19 | (13) | 0.02 |
2010–2015 | 131 | (88) | 130 | (87) |  | |
Location | Cervical | 1 | (1) | 1 | (1) | 0.00 |
Noncervical | 148 | (99) | 148 | (99) | Â |