Novel Hybrid 18f- FDG PET/MR Imaging in Radiotherapy Planning in Lingual Cancer Patients

Abstract

Patients with oral cavity cancer frequently experience recurrence in the regional lymph nodes. Postoperative chemoradiotherapy is recommended for the patients with pathological high-risk features such as extra-capsular extension in salvage neck dissection. Irradiation of the initial primary tumor bed may increase adverse events such as stomatitis or taste disorder, and may deteriorate patients' quality of life. The purpose of this study was to clarify the incidence of local recurrence and factors associated with it as a reference to determine the appropriate clinical target volume. Materials/Methods: We retrospectively reviewed 42 patients who received postoperative radiotherapy or chemoradiotherapy after salvage neck dissection for recurrent cervical lymph node metastases from oral cavity cancer at a single institution between 2007 and 2016. All patients received postoperative radiotherapy with simultaneous integrated boost intensitymodulated radiation therapy. The prescribed dose was 66 Gy in the highrisk planning target volume (PTV), 60 Gy in the intermediate-risk PTV, and 54 Gy in the low-risk PTV. Results: The median interval between initial surgery and salvage neck dissection was 6.5 months (range: 1.6-95.5). Pathological extra-capsular extension of recurrent lymph node metastases was noted in 39 patients (93%). Thirty patients (71%) received concurrent chemotherapy. The primary tumor bed was included in the high-risk clinical target volume (CTV) in one patient (2%), in the intermediate-risk CTV in 21 patients (50%), and in the low-risk CTV in 10 patients (24%), whereas the primary tumor bed was not included in the CTV in ten patients (24%). The median follow-up periods for censored patients were 78.2 months (range: 1.9-102.0). The 5-year overall and recurrent-free survival rates calculated from the initiation of radiotherapy were 60.0 and 51.0%, respectively. Up until the final follow-up, local recurrence had been noted in five patients (12%). Among 19 patients whose interval between initial surgery and salvage neck dissection was 6 months or shorter, five patients (26%) experienced local recurrence, whereas none of the 23 patients whose interval was longer than 6 months experienced local recurrence (p Z 0.014). No patients whose primary tumor bed has not been included in the CTV experienced local recurrence. Conclusion: Local recurrence was less frequent in patients who received postoperative radiotherapy after salvage neck dissection. In case the interval between initial surgery and salvage neck dissection is longer than 6 months, omission of the primary tumor bed may be considered.