P39.01 Long-Term Outcomes and Characteristics of Unresectable Locally Advanced Thymic Malignancies

Abstract

Surgical resection of patients with thymic malignancies with extensive local invasion can be challenging, and the benefit resulting from an incomplete resection is unclear. We sought to define the characteristics, treatment approaches and reasons for unresectability in patients with localized, unresectable thymic tumors and analyze their long-term outcomes Retrospective review of patients with localized, unresectable thymic tumors treated at our institution between 1996-2019. Patients who had surgical exploration only without any resection, surgical exploration with incomplete (R2) resection, and patients who were deemed unresectable and treated non-operatively were included in the study cohort. We analyzed demographics, radiographic findings, pathology, treatment details, and patterns of progression and survival. Descriptive statistics and Kaplan-Meier survival analyses were performed Fifty-nine patients were treated over the study period, 32 with thymoma (54%), 23 with thymic carcinoma (39%) and 4 with thymic carcinoid (7%). Almost all patients were TNM Stage III or IV. Nine patients (15%) were treated non-surgically (NS) and underwent definitive radiation therapy or chemoradiotherapy alone, 14 (24%) patients had surgical exploration only (EO) without resection, and 36 (61%) patients had surgical exploration with incomplete resection (IR). Among the patients who were explored (EO and IR), the most common intraoperative finding was invasion of great vessels or the myocardium (66%), disseminated pleural or lung metastases (14%), or both local invasion and intrathoracic dissemination (14%). Among the NS group, patients were deemed unsuitable for surgery due to the presence of unresectable metastases (22%), great artery involvement (56%), great vein involvement (11%), or severe comorbidities (11%). Forty-one patients (69%) developed progression (31 loco-regional; 10 distant) while 18 patients (31%) had stable disease during the observation period. Patients with unresectable thymoma had significantly longer overall survival (OS, p=0.02) compared to thymic carcinoma (median OS thymoma = 7.5 years; thymic carcinoma = 3.2 years). There was no significant difference in OS (p=0.2; Figure) or PFS (p=0.1) between IR and NS/EO patients. The median OS for IR patients was 4.6 years and 6.9 years for NS/EO patients. The median PFS was 0.8 years for patients in the IR group, and 1.6 years for those who had no resection (NS/EO) Despite the presence of unresectable locally advanced disease, patients with advanced thymic malignancies exhibited long-term survival regardless of the primary treatment modality. In our series, patients who underwent incomplete surgical resections did not appear to fare any better than patients who underwent exploration only or non-operative treatment