Neoadjuvant therapy for thymic neoplasms reduces tumor volume per 3D-reconstructed images but does not improve the complete resection rate

Objectives Complete resection of thymic neoplasms is important for achieving a favorable prognosis; however, the efficacy of neoadjuvant therapy remains controversial. We investigated the effect of induction therapy on complete resection and survival using 3-dimensionally reconstructed images to measure tumor volume. Methods Eighty-nine patients who underwent surgical resection for Masaoka-Koga stage III–IV thymic neoplasms between January 2000 and December 2013 were enrolled, including 71 and 18 in the primary surgery and neoadjuvant therapy groups, respectively. Baseline characteristics, postoperative outcomes, and survival rates were analyzed. Moreover, baseline and post-neoadjuvant therapy tumor volumes were compared among patients in the neoadjuvant group. Results Adjacent mediastinal structure invasion was significantly rarer in the primary surgery group than in the neoadjuvant group (1.27±1.09 vs. 2.61±1.42, p<0.001). On subgroup analysis of patients who underwent neoadjuvant therapy, tumor volumes decreased significantly from 206.08±132.32 cm 3 to 81.25±71.24 cm 3 post-therapy (p = 0.001). Interestingly, only the pre-neoadjuvant tumor volume was significantly associated with complete resection, while the post-neoadjuvant volume was not (p = 0.012 and p = 0.458, respectively). Moreover, despite significantly reduced tumor volumes, patients in the neoadjuvant therapy group did not exhibit significantly different R0 resection rates (odds ratio 1.490, p = 0.581) or overall survival (p = 0.285) compared to those in the primary surgery group. Conclusions Neoadjuvant therapy does not significantly influence the R0 resection rate or overall survival relative to primary surgery. Nevertheless, it may by useful for patients planning surgical resection because it significantly reduces the presurgical tumor volume and extent of invasion.