Validity and utility of cat classification system for oncological mandibular defects A multi-institutional study

Background: We have previously proposed the CAT classification system, a simple and clear-cut system for classifying segmental mandibular defects after oncological surgery: “C” refers to the loss of the condylar head of the mandible, “A” the mandibular angle and “T” the mental tubercle. Here, we report a statistical and mathematical taxonomical study on the validity and utility of the classification system. Methods: Data were collected from 17 medical institutions in Japan on 259 patients who had undergone surgical ablation and simultaneous microsurgical oromandibular reconstruction (osteocutaneous free flap or soft tissue free flap with reconstruction-plate) attributed to head and neck cancer. The mandibular defects were classified according to the CAT system and the two commonly used systems HCL and Urken, and the validity and utility of the CAT system were tested as follows: 1) the tendency among the numbers of the three reference points of the CAT system (C, A and T) and the esthetic outcome of each patient were analyzed by Jonckheere's trend test, 2) each of the classified patterns of the three systems was analyzed by cluster analysis based on the esthetic results using Ward's method. Results: 1) There was a statistically significant trend among the numbers of the three reference points in the CAT system and the esthetic outcome, 2) each of the grouped clusters in the CAT system was clinically explicable and demonstrated a significant difference in the esthetic outcome; the two other systems did not yield such information. Conclusion: The CAT classification system is valid and useful for oncological segmental mandibular defects.