(P 507) PRIMARY CHEST WALL TUMORS OF MESENCHYMAL ORIGIN. EXPERIENCE OF A REFERENCE UNIT

Objective: Primary chest wall tumors of mesenchymal origin are rare representing only 1% of all malignant tumors in adulthood. Histologically they are a very heterogeneous group which makes the diagnostic process difficult.
The aim of this study is to analyze the data of patients diagnosed with primary tumor of mesenchymal origin who underwent surgery in a reference unit. In addition, we want to see how histological type and type of resection influence overall survival and disease-free survival at 1, 3 and 5 years.

Methods: Observational and retrospective study to analyze the series of patients who underwent surgery with a diagnosis of primary chest wall tumor of mesenchymal origin during the period 2012-2022 (n=40 patients). Demographic variables, comorbidities, tumor size, histology and histological grade, type of resection, surgical margins and reconstruction technique, postoperative complications, adjuvant and/or neoadjuvant therapy, duration of follow-up and survival were recorded. An analysis of overall survival and disease-free survival at 1, 3 and 5 years was performed by log-rank test.

Results: The median age was 57 years (SD±19 years). Forty percent (N=16) had a previous oncologic history and 69% of patients had less than 2 comorbidities at the time of surgery. In 37 patients (93%) of the tumors operated on, the histological diagnosis was sarcoma, 13 patients (33%) were of bone origin and 27 patients (68%) were soft tissue sarcomas (Image 1). One patient was excluded from the study due to loss to follow-up.The median tumor size was 9 cm (SD±5.6cm). Fifty-three percent of the tumors (N=21) were of intermediate-high histologic grade. Resection was marginal in 40% of cases. Twenty-two patients required chest wall reconstruction. In 19 patients a synthetic or biological mesh was used and in 10 of them a rigid reconstruction with titanium rods (N=8) or titanium mesh (N=2) was also performed. In 17 patients a flap was used to cover the defect, the most commonly used being the pedicled latissimus dorsi flap (N=7). Flap infection resulted in bar removal in 2 patients. Twenty-five percent (N=10) underwent induction treatment and 45% (N=18) adjuvant treatment with chemotherapy and/or radiotherapy. Thirty percent (N=12) of the patients had local recurrence and 45% (N=18) had distant metastases. The median overall survival time was 68.1 months (95% CI 49.8-86.4). Overall survival at 1 year was 87%, at 3 years was 58% and at 5 years was 46%. The disease-free time was 15.9 months (CI 95% 3.3- 28.6) with 60% at 1 year, 40% at 3 years and 36% at 5 years (Table 1).
As influential factors in OS and DFS, the resection margin and histological type were analyzed. In spite of not obtaining a statistically significant difference, a tendency to lower overall survival was observed in tumors of soft tissue origin and in those where resection was not complete (Image 2).The same is true for disease-free survival. Tumors of soft tissue origin or those with marginal or incomplete resection had a shorter disease-free time (Image 3).

Conclusion: - In this group of patients, overall survival at 5 years was 46%, while disease-free survival at 5 years was 36%.
- Sarcomas with soft tissue origin and marginal or incomplete resection are two factors that negatively influence overall survival and disease-free survival.
- Given the low prevalence of these tumors, a multidisciplinary approach in reference units is essential to guarantee a correct diagnostic and therapeutic process.