AB044. Surveillance trends after resection for thymic malignancy

Background: Little is known of optimal postoperative surveillance methods for thymic malignancies, and current guidelines are based on expert opinion. This is the first known attempt to characterize surveillance imaging in an integrated healthcare system after resection for thymic malignancy.

Methods: All patients who underwent thymectomy for thymic malignancy at Kaiser Permanente Northern California from February 1, 2007, to June 30, 2023, were examined, excluding those who died within 90 days post-surgery. We assessed patient characteristics, including Masaoka stage and margin status, along with patterns of tomographic chest imaging from 90 days post-surgery until June 30, 2024. Based on National Comprehensive Cancer Network guidelines (version 1.2024), we defined a patient to be adherent to annual surveillance if the patient was scanned within a designated timeframe, defined as within 3–18 months for the first year and within 12 months for each subsequent year, up to 10 years post-surgery. In each timeframe, patients were censored in the analysis if they were lost to follow up, developed a recurrence, died, or had insufficient follow up time.

Results: We identified 334 patients (54.8% female, median age at surgery: 61.5 years, 15.1% thymic carcinoma) with a combined total of 1,636 studies performed (average 0.80 scan/patient/year). Median follow up was 8.7 years; 89.8% of all surgeries were performed by a board-certified thoracic surgeon. Annual surveillance rates decreased rapidly as time lapsed from surgery, with 85.4%, 47.3%, and 27.8% at the 1^st, 5^th and 10^th years of surveillance for thymoma respectively, and 100%, 90.6% and 61.1% at the 1^st, 3^rd, and 5^th years of surveillance for thymic carcinoma respectively. Seventeen patients did not have any tomographic chest imaging, despite receiving other healthcare. During follow-up, 30 patients recurred, of whom 27 (90%) were diagnosed by a surveillance scan without symptoms (median time to recurrence: 31 months). Surveillance adherence rates were not statistically different by Masaoka stage or margin status.

Conclusions: Annual surveillance rates decreased rapidly after surgery for thymic malignancies. Most recurrences were diagnosed on surveillance studies, which suggests the need for postoperative surveillance for thymic malignancies.

Keywords: Thymic malignancy; surveillance; survivorship