(P 378) INGUINAL SARCOMAS - A RETROSPECTIVE ANALYSIS OF DIAGNOSIS, CLINICAL FEATURES, TREATMENT PATTERNS AND OUTCOMES (I-SARC): A STUDY BY TARPSWG

Objective: Inguinal sarcoma is a rare soft tissue malignancy that is frequently misdiagnosed at initial presentation. Due to the rarity of this disease, there is no published consensus regarding the diagnosis and management of inguinal sarcomas. We aimed to describe patterns of occurrence, histology, and treatment modalities of inguinal sarcoma through an international collaboration of high-volume sarcoma centers.

Methods: We conducted a retrospective analysis of adult patients with primary inguinal soft tissue sarcomas diagnosed between January 2005 and December 2021 that underwent resection with curative intent at a Transatlantic Australasian Retroperitoneal Sarcoma Working Group (TARPSWG) participating institution. “Inguinal sarcoma” was defined as a tumor of mesenchymal origin (i.e. do not arise from viscera such as the ovary, bowel, kidney, etc.) that arises within the boundaries of the inguinal canal (namely between the superficial and deep inguinal rings) or the soft tissues overlying the inguinal canal allowing for minor extension proximally into the retroperitoneum or distally to the gonads. Patients with visceral sarcomas, bony sarcomas, and tumors that arose from other sites and secondarily involved the inguinal region were excluded. Descriptive statistics were calculated with SPSS v.27. Overall survival was defined as time between definitive resection and last known follow up date.

Results: Twenty-six institutions from 15 countries contributed 528 patients (male, 81.3%). Of these, 229 (43.4%) underwent an initial operation that resulted in unintended resection of the primary sarcoma (i.e. “whoops procedure), and 33 (6.4%) had a history of prior primary sarcoma. Preoperative imaging was obtained in the majority of patients; 396 had a CT (75.6%), 258 had an MRI (49.1%), and 81 had a PET/CT (15.4%). 26.4% (139) of patients had evidence of vascular involvement on preoperative imaging. Biopsy histology was distributed as follows: de-differentiated liposarcoma (109, 26%), well-differentiated liposarcoma (55, 13.1%), leiomyosarcoma (37, 8.8%), undifferentiated pleomorphic sarcoma (27, 6.4%), solitary fibrous tumor (11, 2.6%), and malignant peripheral nerve sheath tumor (9, 2.1%). 30 (5.6%) patients had metastatic disease at the time of surgery most commonly lung (n=12, 40%) and remote lymph node basins (13, 43.3%). 51 (9.7%) patients underwent preoperative chemotherapy, and 137 (26.1%) patients underwent preoperative radiotherapy. Definitive resections were performed by surgical oncologists (452, 85.8%), urologists (40, 7.6%), or general surgeons (19, 3.6%). Negative margins (R0) were achieved in 369 patients (70.4%), while 132 (25.2%) had microscopically positive (R1) margins and 9 (1.7%) had macroscopic residual disease. 51 (9.2%) patients required vascular resection or reconstruction. Margin status was statistically different (P = 0.013) when stratified by “whoops procedure” prior to definitive surgery. R0 resection occurred in 73.4% (n=166) of surgeries after a “whoops procedure” and 68.1% (n=201) of patients undergoing primary resection. Median size was 75mm (range, 10mm-300mm). De-differentiated liposarcoma (164, 31.1%) was the most common final pathologic diagnosis. Most patients did not undergo postoperative chemotherapy (487, 93.1%) or radiotherapy (404, 77.5%). 179 patients have been diagnosed with recurrence: 42.5 % (76) with locoregional recurrence and 57.5% (103) with distant recurrence. At time of data collection, 336 patients (63.6%) were alive without evidence of disease, 52 (9.8%) were alive with disease, 94 (17.8%) died due to their disease, and 40 (7.6%) died of other causes. Median unadjusted overall survival was 50.6 months (range, 12 days to 18.46 years).

Conclusion: This study provides the largest, international experience describing the characteristics, management, and outcomes of inguinal sarcoma treated with surgical resection to date. Notable findings are male predominance, vascular involvement and high rate of initial unintended resections. However, acceptable oncologic outcomes are achieved following definitive multidisciplinary treatment at specialty centers.