# Recurrence Patterns, Treatment Outcomes, and Prognostic Factors of Thymic Carcinoma: A Multicenter Study

## TL;DR

This study analyzed 101 thymic carcinoma patients to understand recurrence patterns, treatment outcomes, and factors affecting survival, finding that cancer stage is the most important predictor of outcomes.

## Contribution

The study provides stage-specific insights into treatment outcomes and highlights the importance of multidisciplinary strategies for thymic carcinoma.

## Key findings

- Stage was the only significant factor influencing overall survival, progression-free survival, and local recurrence-free survival.
- Treatment modality only impacted local control, not overall survival or progression-free survival.
- Stage IV patients had similar outcomes regardless of whether they received surgery plus radiotherapy or definitive radiotherapy.

## Abstract

Due to the rarity of thymic carcinoma, the lack of prospective clinical trials has led to numerous database-based studies. Consequently, detailed analyses and adverse events remain largely underinvestigated. Treatment strategies for thymic carcinoma differ slightly from those for other cancers and are based more on resectability than stage. We conducted this multicenter retrospective study of thymic carcinoma to clarify its recurrence patterns, treatment outcomes, prognostic factors, and adverse events. The study examined 101 patients: 72 underwent surgery combined with radiotherapy, and 29 received definitive radiotherapy. Stage was the sole significant factor influencing all outcomes, including overall survival; treatment modality impacted only local control. Stage IV patients had similar outcomes whether they received surgery plus radiotherapy or definitive radiotherapy. This study emphasizes the importance of stage-specific, multidisciplinary strategies to optimize outcomes, especially for stage IV patients, and it recommends prospective studies for validation.

Objectives: This multicenter study aimed to clarify the recurrence patterns; treatment outcomes; and prognostic factors of thymic carcinoma, a rare cancer. Methods: We analyzed 101 patients with thymic carcinoma who underwent multidisciplinary treatment, including radiotherapy. The median age was 62 years, with 27 patients in stage I–II; 44 in stage III; and 30 in stage IV by the TNM classification. Seventy-two patients underwent surgery with radiotherapy; and 29 patients underwent definitive radiotherapy. Image-guided radiotherapy (IGRT) and elective nodal irradiation (ENI) were used for 35 and 23 patients, respectively. Local recurrence-free survival (LRFS); progression-free survival (PFS); and overall survival (OS) were calculated, and univariate and multivariate analyses were performed. Results: With a median follow-up of 68 months, we observed 17 local recurrences; 27 regional recurrences; and 35 distant metastases. The 5-year LRFS; PFS; and OS were 82%, 41%, and 76%, respectively. Multivariate analysis revealed that stage was the only factor associated with LRFS; PFS; and OS (p = 0.040; p < 0.0001; and p = 0.048, respectively), while treatment modality was associated with only LRFS (p = 0.015). IGRT and ENI were also associated with LRFS (p = 0.002 and 0.013, respectively). PFS and OS of stage IV patients were comparable between the surgery with radiotherapy and definitive radiotherapy groups (p = 0.99 and 0.98, respectively). Conclusions: Our results suggest the importance of stage-specific treatment strategies rather than resectability, especially for stage IV patients. These results should be validated in a prospective study. Our results also suggest that radiotherapy methods influence recurrence