Patterns of relapse after postoperative radiotherapy in patients with oral cavity cancer and a flap

Reconstructive surgery with a flap is standard practice in advanced oral cavity squamous cell carcinoma to restore essential functions. However, these functions may be compromised by postoperative radiotherapy. This study evaluates relapse patterns and treatment-related toxicity in these patients.

A multicentre 2018-2023 study included 247 patients with oral cavity squamous cell carcinoma. Uni- and multivariate analyses estimated the cumulative incidence of locoregional failures, survival rates, and prognostic factors.

Among the patients, 74.0 % had pT3-4 tumours, 78.5 % had free flaps, regional pedicled flaps (12.6 %), or local flaps (8.5 %). Flaps were not delineated on planning CTs. Median follow-up for living patient was 36.8months. Fifty-eight patients (23.0 %) had involved soft-tissue margins; no correlation was found between margin involvement, stage, or flap type. Forty patients experienced local relapse within a median of 8.23months. Local relapse rates were higher in patients with involved (28.6 %) versus clear margins (9.3 %, P<0.004). Two-year locoregional relapse and survival rates were 17.8 %, and 74.3 %, respectively. Performance status greater than 1, locoregional relapse, and distant relapse were associated with poorer survival. Coregistration of planning-relapse CTs is challenging due to flap changes, limiting relapse pattern analysis. Subgroup analysis of locoregional relapses (14 out of 53) at the main contributing centre revealed that five relapses occurred at the native tissue-flap junction, with minor flap involvement in two cases and no intraflap failure. All other relapses occurred outside the flap.

Involved margin rates correlating with increased local relapse risk and were not different according flap type. Further investigation into flap segmentation and planning optimization is needed. The OPTIFLAP trial (NCT06798922, PHRC2024) aims to determine whether radiotherapy can be optimized to spare flaps without increasing the risk of locoregional failure.