Preoperative examination items | Group A | Group B | Total | χ2value | P value | Fisher’s exact probability | |||
---|---|---|---|---|---|---|---|---|---|
 | Number | Percentage (%) | Number | Percentage (%) |  | ||||
Tumor size estimated by palpation | ≤20 mm | 752 | 93.07 | 56 | 6.93 | 808 | 5.842 | 0.016 | – |
 | >20 mm | 1,408 | 95.46 | 67 | 4.54 | 1,475 |  |  |  |
Total | 2,160 | Â | 123 | Â | 2,283 | Â | Â | Â | |
Lymph node status determined by palpation | No metastasis (N0) | 1,470 | 95.08 | 76 | 4.92 | 1,546 | 0.315 | 0.575 | – |
 | Metastasis (N1–3) | 566 | 94.49 | 33 | 5.51 | 599 |  |  |  |
Total | 2,036 | Â | 109 | Â | 2,145* | Â | Â | Â | |
Molybdenum-target X-ray | Not used | 1,368 | 96.75 | 46 | 3.25 | 1,414 | 12.333 | <0.001 | – |
 | Used | 655 | 93.44 | 46 | 6.56 | 701 |  |  |  |
Total | 2,023 | Â | 92 | Â | 2,115* | Â | Â | Â | |
Ultrasonography | Not used | 612 | 97.45 | 16 | 2.55 | 628 | 6.832 | 0.009 | – |
 | Used | 1,421 | 94.92 | 76 | 5.08 | 1,497 |  |  |  |
Total | 2,033 | Â | 92 | Â | 2,125* | Â | Â | Â | |
MRI | Not used | 2,083 | 95.16 | 106 | 4.84 | 2,189 | – | – | 0.088 |
 | Used | 65 | 90.28 | 7 | 9.72 | 72 |  |  |  |
Total | 2,148 | Â | 113 | Â | 2,261* | Â | Â | Â |