AB038. A 10-year retrospective review of recurrent thymomas: a single-centre experience

Background: Thymomas are the most common anterior mediastinal tumours, however, overall incidence remains rare. Because of their rarity and low malignant potential, recurrence of thymomas is rarer still. Data on long-term outcomes thus remains limited. We present a single-centre review of recurrent thymoma cases over 10-years. Our objective is to assess the clinical characteristics, management, and long-term outcomes of recurrent thymoma, with a focus on recurrence patterns, histological changes, and the role of surgical intervention in recurrent disease.

Methods: Retrospective review was conducted using prospectively collected data of all patients diagnosed with recurrent thymomas at our centre between January 2014 and December 2024. A total of 77 patients underwent surgical treatment for thymoma. Of these, 10 patients had recurrence. While 3/10 opted for and remain under active surveillance, 7/10 underwent further surgery for recurrence. Data including demographic characteristics, presence of paraneoplastic disorders, initial and recurrent tumour histology [World Health Organization (WHO) classification], timing and location of recurrence, and clinical outcomes were analyzed.

Results: Equal gender-distribution was noted (5 males: 5 females). Myasthenia gravis was diagnosed in 5/10. Mean age at time of recurrence was 58.3 years. The median time to recurrence was 9.8 months (but ranged up to 192 months). All recurrences were picked up on follow-up cross-sectional imaging and multidisciplinary team (MDT) discussion. Histology from original surgery showed complete macroscopic resection (R0/R1) in 8/10 patients. However, the majority of them were noted to have advanced stage (stage III/IV) thymomas on initial histology. Of 7 patients who underwent further surgery, 2 patients had different WHO grade on recurrent histology: one had a recurrence of B3 in a previously predominant B2 tumour, while another had a recurrence of B2 thymoma in a previously type A thymoma. The average length of stay following recurrence operation was 4.06 days. Despite the complexity of re-interventions, there was no peri-operative mortality. Unfortunately, 1 patient passed away from unrelated cause.

Conclusions: Although historically we follow-up thymomas for 10 years, our experience with recurrent thymomas over a decade supports the need for lifelong surveillance, as recurrence may emerge years after initial resection in these indolent tumours. In addition, imaging follow-up allows early detection and possible further surgical intervention. Where surgical resection is feasible, we would advocate proceeding with the goal of achieving complete excision of recurrent disease. Nonetheless, MDT discussion and individualized multimodality treatment/surveillance are crucial for optimizing long-term outcomes in these rare advanced recurrent thymomas.

Keywords: Thymoma; recurrent thymoma; thymectomy; rare tumours