Abstract 1530P
Background
Primary soft tissue or bone METs are very rare neoplasms. Data on prognosis and outcome are sparse.
Methods
We retrospectively reviewed the METs managed by the French Sarcoma Group between 1990 and 2019. Glandular and visceral tumors were excluded. Survival curves for operated patients were calculated using the Kaplan-Meier method. Univariate analysis was performed using the logrank test and the Cox proportional hazards model for the identification of prognostic factors (PF).
Results
A total of 83 patients were treated in 14 centers. In 7 cases, MET was first misdiagnosed with mimick. Median age was 43 years (3-85). There were 45 women (54%). METs occurred in bone in 4 cases (5%) and in soft tissue in 79 (95%). The most common primary sites were the lower limbs (33, 40%), the upper limbs (23, 28%), and the trunk wall (15, 18%). Median size was 50 mm (7-400). 24 (30%) were superficial tumors. Initial N1 (pathological lymph nodes) and M1 (distant metastasis) status were diagnosed in 4 (5%) and 5 (6%) cases, respectively. 75 patients (90%) underwent curative-intent surgery with 32 (39%) R0 resection, 21 (25%) R1 and 5 (6%) R2. 5 patients (6%) received perioperative chemotherapy, 3 (4%) preoperative radiotherapy, and 18 (22%) adjuvant radiotherapy. Median follow-up was 58 months. The overall survival (OS) rate at 6, 12 and 24 months was 96% [88-99], 93% [85-97] and 90% [80-95], respectively. Local relapse-free survival at 6, 12 and 24 months was 90% [80-95], 80% [70-88], and 70% [58-79], respectively. Metastasis-free survival at 6, 12 and 24 months was 86% [77-92], 85% [75-91] and 81% [70-88], respectively. Age ≥ 50 years was the only PF for OS (HR = 4.8 [1.0-22.2], p=.04). We found three PF for local relapse: misdiagnosis before treatment (HR = 3.7 [1.3-10.0], p=.01), surrounding tissue invasion (13.9 [1.6-118.6], p=.02), and multifocal tumor (HR = 5.6 [2.0-15.3], p=.0009). The two PF for metastasis were surrounding tissue invasion (17.4 [2.0-156.0]; p=.01) and mitotic count (6.0 [1.6-23.0], p=.009). Perioperative radiotherapy and R0 resection did not influence the outcome of operated METs.
Conclusions
METs are likely to be a particular entity distinct from sarcomas. Further clinical investigation is required to identify biological prognostic factors.
Clinical trial identification
Editorial acknowledgement
Legal entity responsible for the study
Centre Oscar Lambret.
Funding
Has not received any funding.
Disclosure
All authors have declared no conflicts of interest.