A critical reflection of radiotherapy on osseous free flaps in mandibular segmental resection and immediate reconstruction in locally advanced oral squamous cell carcinoma: A cohort study.

[BACKGROUND AND PURPOSE] With standard radiotherapy protocols after R0 resection of advanced local oral squamous cell carcinoma (OSCC) and primary reconstruction of segmental defects, a high radiation dose is applied to healthy tissue in autologous microvascular free flaps. Considering the potential consequences of flap complications and associated surgeries for patients, data is lacking on whether postoperative radiotherapy (PORT) of the flap volume is indicated at all.

[MATERIALS AND METHODS] Patients with segmental mandibular resection and immediate reconstruction with osseous free flaps due to advanced OSCC between 2012 and 2022 were analyzed retrospectively regarding overall (OS), disease-free survival (DFS), local failure-free survival (LFFS), the need for secondary surgeries as well as flap complications and compared between patients with and without PORT in a matched-pair approach with occurrence of flap complications as a primary endpoint.

[RESULTS] 105 patients matched the inclusion criteria. The maximum follow-up period was 60 months. 68 patients received PORT. 74 patients were included in the final analysis. No case of disease recurrence inside the free flap was recorded. There were no significant differences in DFS (p = 0.21), OS (p = 0.33) and LFFS (p = 0.6) between both cohorts. Occurrence of osteoradionecrosis (p = 0.03) and bone exposure (p = 0.003) was higher in irradiated flaps. In patients with PORT, the demand for secondary surgeries due to flap complications was significantly higher (p = 0.009). Radiation doses were not increased in patients with flap ORN.

[CONCLUSION] PORT is associated with higher flap complications and need for secondary surgeries in advanced stage OSCC. Given a recurrence rate of zero inside the flap without PORT and the improbability of recurrence within healthy transplanted tissue, the usefulness of applying high radiation doses to this vulnerable tissue is questioned. Further refinements of RT planning should be evaluated and tested in a RCT trial.