Unradical Surgery for Locally-Advanced Thymoma: Is it time to evolve Perspectives?

•Radical resection is currently the mainstay for thymoma’s treatment.•Locally-advanced thymomas are more challenging for surgeons.•Complete resection may not always be achieved, due to neighboring organs’ invasion.•Oncologic outcomes of unradical surgery with curative-intent poorly investigated.•Incomplete resection has proved effective in a contest of multimodality strategy. Nearly-one-third of thymomas are locally-advanced at diagnosis. The traditional dogma that surgery is justified in case a complete resection can be achieved has remained unmovable until today. This study aimed to investigate feasibility and oncologic efficacy of incomplete resection for locally-advanced thymomas in a contest of multimodality therapy. A retrospective analysis was conducted using data of prospectively maintained thymomas database in a single high-volume centre. Data on 285 consecutive patients undergoing surgery for stage III and IVa thymomas between 1995 and 2019 were reviewed. Patients who underwent incomplete resection with curative-intent (removal of at least 90% of tumour burden) were included. Long-term outcomes and predictors of cancer-specific survival (CSS) and progression-free survival (PFS) were analyzed. Secondary endpoint was to assess adjuvant therapy efficacy. The study included 79 patients, 60 with microscopic residual tumour (76%, R1) and 19 with macroscopic residual disease (24%, R2). Masaoka-Koga stage was: III in 41 patients (52%) and IVa in 38 (48%). Histology was B2-thymomas (n = 31, 39.2%) followed by B3 (n = 27, 34.2%). Five- and 10-years CSS was 88% and 80%. Seventy patients (90%) underwent adjuvant treatment; they showed CSS comparable to radical resected patients (5-years: 89.1% vs 98.9%, respectively; 10-years: 81.8% vs 92.7%, respectively, p = 0.43). The site of residual disease, Masaoka-Koga stage and WHO histology did not affect prognosis. Stepwise multivariable analysis confirmed adjuvant therapy as a favourable CSS prognostic factor (HR, 0.51; 95% CI, 0.33–0.79, p = 0.003). Stratifying by subgroups, R2-patients who received postoperative chemo(radio)therapy (pCRT) showed a significantly better prognosis than R2-patients treated by consolidation radiotherapy alone (10-years CSS: 60%, p