Surgery Followed by Entire Hemithoracic Radiation Therapy in Patients With Thymoma and Pleural Dissemination: A Prospective Phase 2 Study.

PURPOSE: The management of patients with thymoma and pleural dissemination remains challenging. We conducted a prospective phase 2 study to investigate the safety and efficacy of surgery followed by entire hemithoracic radiation therapy in these patients.

METHODS AND MATERIALS: Patients with thymoma and pleural dissemination (de novo or recurrent) were enrolled. After macroscopic resection, intensity modulated radiation therapy of 14 Gy in 14 fractions was delivered to the entire hemithorax. An additional dose of 30 Gy in 15 fractions was delivered to the mediastinal tumor bed if the stage of the primary tumor was higher than T2.

RESULTS

Between April 2020 and December 2021, 71 patients completed the study protocol. There were 30 men and 41 women, with a median age of 46 years (range, 26-75). There were 32 de novo cases and 39 recurrent cases. During a median follow-up of 57 months, 2 patients (2.8%) died: one from disease progression and the other from heart disease. A total of 34 patients (47.9%) developed disease progression, including pleural recurrence inside the radiation field (n = 24) and outside the field (n = 10). The median progression-free survival was 50 months (95% CI, 45.95-54.39). The 3- and 5-year progression-free survival rates were 68.9% (95% CI, 56.7%-78.3%) and 50.8% (95% CI, 38%-62.3%), respectively. The 3 and 5-year recurrence-free survival rates (defined as no relapse inside the radiation field) were 78.8% (95% CI, 67.4%-86.7%) and 66.5% (95% CI, 53.3%-76.7%), respectively. The 5-year overall survival rate was 98.6%. Nausea, fatigue, and vomiting were the most frequent toxicities, and most were mild in severity.

CONCLUSIONS

Surgical resection followed by entire hemithoracic radiation therapy is a safe treatment approach for patients with thymoma and pleural dissemination, yielding promising local control. The optimal dose and target volume of radiation therapy warrant further investigation.