Postoperative Adjuvant Radiation Therapy Using a Simultaneous Integrated Boost Technique Applied with Helical Tomotherapy in Masaoka-Koga II-III Thymomas Patients

Abstract

Thymomas are the most common tumors of the anterior mediastinum despite their overall rarity. Surgical resection remains the mainstay for the management of thymic tumors. Dose-intensified adjuvant radiotherapy (RT) has achieved a favorable biochemical control rate with increased toxicity. To optimize adjuvant radiotherapy scheme, simultaneous integrated boost technique applied with helical Tomotherapy was used in Masaoka-Koga II-III thymomas patients. Nineteen patients with Masaoka-Koga II-III thymomas treated by radical resection and adjuvant RT using helical Tomotherapy between 01/2014 and 12/2015 were enrolled. All initial operations were completed within one month after diagnosis, comprising gross total resection (GTR) in 12 patients, subtotal resection (STR) in 7 patients. RT was administered using a simultaneous integrated boost (SIB) to the area at risk, different targets and different dose fractionated regions were planned through the art of anatomic-dose painting in the light of surgery results. Totally 60Gy (30 fractions of 2.0 Gy) were treated to GTVtb for patients with STR. The whole tumor bed was treated with a dose of 54 Gy (30 fractions of 1.8 Gy). Primary endpoints were acute and late radiative pneumonitis and pericarditis. Secondary endpoints included disease free survival (DFS) and overall survival (OS). The median follow-up was 19 months (range, 8–41 months). Three (15.8%) and one (5.3%) patients experienced acute grade 2 radiative pneumonitis and pericarditis, respectively. One patient (5.3%) had late grade 2 radiative pneumonitis, no late grade 2 radiative pericarditis nor any grade 3 acute or late radiative pneumonitis or pericarditis events were observed. A total of five patients (26.3%) experienced a biochemical recurrence with the 2-year DFS being 74%. The 2-year OS for all investigated patients is 85%. No statistic significant difference in DFS and OS was found between patients with GTR or STR. Postoperative adjuvant RT for Masaoka-Koga II-III thymomas patients with a risk adapted dose-intensified SIB using helical tomotherapy is feasible and associated with favorable acute and late radiation pneumonitis and heart toxicity rates.