(P 204) IMPACT OF UNPéLANNED EXCISION ON THE SURVIVAL OF SARCOMA PATIENTS - A TARGET TRIAL EMULATION

Objective: The misdiagnosis and subsequent unplanned whoops resection (UE) of sarcomas, under the presumption of benignity, constitutes a significant clinical challenge. Therefore, we aimed to assess the association between UE compared to planned excision (PE) and local-recurrence free survival (LRFS), metastasis free survival (MFS), cancer specific survival (CSS) and overall survival (OS) by emulating a target trial.

Methods: We included patients who underwent either UE or PE and had a histologically confirmed sarcoma. Exclusion criteria were history of any malignant neoplasm within the past 5 years (n = 36), any history of leukaemia (n = 2), and age below 16 years (n = 10). Furthermore, desmoid tumors were not included in this study. We have emulated a target trial that compared UE and PE and assessed its impact on LRFS, MFS, CSS and OS. Multivariable Cox regression analyses adjusting for dignity, sarcoma type, anatomic region, tumor size and grade were performed. Inverse probability of treatment weighting was done.

Results: We have included 429 consecutive patients, 323 (75.3%) underwent PE and 106 (24.7%) underwent UE. We found that patients with UE had significantly higher hazards of local recurrence, HR 7.49 (2.88, 19.49), p < 0.001, compared to patients that underwent PE. We found no association between UE compared to PE and MFS (HR 1.42 (0.40, 4.98), p = 0.58), OS (HR 1.47 (0.42, 5.16), p = 0.55) or CSS (HR 1.47 (0.37, 5.94), p = 0.59).

Conclusion: We employed the target trial emulation framework that aims to decrease bias that usually stems from the analysis of observational data. We found no significant differences in MFS and OS between the UE and PE groups. These findings suggest that, despite the adverse impact of UEs on local control, subsequent therapeutic interventions might mitigate the long-term risks of metastasis and mortality. However, the increased risk of local recurrence after UE illuminates a crucial systemic flaw in the referral to specialized sarcoma networks.