Application of anatomy unit resection surgery for lateral basicranial surgical approach in oral squamous carcinoma.

Background: The basicranial region lacks definite boundaries and includes various anatomical units. We developed a novel concept of the posterior oral anatomical complex (POAC) to identify these anatomical units in the basicranial region. OSCC with POAC involvement is termed posterior oral squamous cell carcinoma (POSCC) with poor prognosis. The principal aim of this study was to evaluate the effect of anatomy unit resection surgery (AUSR) on patients with POSCC.

Methods: A total of 120 POSCC patients who underwent radical surgical treatment were recruited for this study. These POSCC patients were treated with conventional surgery or AUSR. According to the extent of primary tumor resection in the AUSR group, the lateral basicranial surgical approach can be subdivided into four types: face-lateral approach I, face-lateral approach II, face-median approach or face-median and face-lateral combined approach. Facial nerve function was evaluated according to the House-Brackmann Facial Nerve Grading System.

Results: The overall survival rate was 62.5% and 37.5% in the AURS group and conventional group (hazard ratio: 0.59; p < 0.0001), respectively. The disease-free survival rate was 62.5% and 34.3% in the AURS group and conventional group (hazard ratio: 0.43; p = 0.0008), respectively. The local disease control rate in the AURS group (71.4%) was significantly better than that in the conventional group (34.4%) in present study (p < 0.0001). Compared to the conventional group, all the patients undergoing AURS were classified as T4 stage and presented with more lymph node metastasis (71.4%). A total of 20 patients (face-lateral approach I and face-lateral combined approach) were temporarily disconnected from the temporofacial branch of the facial nerve. Fifteen patients exhibited slight paresis, and five patients presented with moderate or severe paresis. The survival rate of zygomatic arch disconnection was 94.6% (54 of 56 patients).

Conclusion: This lateral basicranial surgical approach based on AUSR improves the survival rate and enhances the local control rate while also preserving a good prognosis without damaging the nerve and zygomatic bone. This surgical approach based on AUSR provides a novel and effective surgical treatment to address POSCC with better prognosis, especially for patients without metastatic lymph nodes.