Letters to the Editor Letters to the Editor 1130-0108/2017/109/7/534-535 REVISTA ESPAÑOLA DE ENFERMEDADES DIGESTIVAS © Copyright 2017. SEPD y © ARÁN EDICIONES, S.L. REV ESP ENFERM DIG 2017, Vol. 109, N.º 7, pp. 534-535 Utility of neoadjuvant therapy in rectal GIST Key words: GIST. Rectum. Imatinib. Neoadjuvant. Local resec- tion. DOI: 10.17235/reed.2017.4751/2016 Dear Editor, A neoadjuvant therapy approach with tyrosine kinase inhib- itors (TKI) in cases of rectal gastrointestinal stromal tumors (GIST) allows a surgical rescue of a high percentage of patients that initially were not candidates for aggressive surgery. Case report A 49-year-old man presented with a tumor located 3 cm to 1 cm from the anal verge. A GIST was confirmed by a biopsy (CD-117: +/DOG1: +). Magnetic resonance imaging (MRI) showed a tumor in the right anterolateral wall of the rectum. 18 F-FDG PET/CT showed an abnormal uptake of the lesion with a maximum standardized uptake value (SUV) of 9 (Fig. 1A). Neoadjuvant treatment with 400 mg/day of imitanib was initiated. Three months later an 18 F-FDG PET/CT was per- formed with the absence of pathological uptake (Fig. 1B). A transanal rectal resection was performed. Pathological anato- my identified tumor cells which were positive for CD-117 and DOG-1 and viable tumor (< 5%) with a tumor free surgical margin (Fig. 2). Eighteen months later, the patient is free of disease. Fig. 1. 18 F-FDG PET/TC before and after neoadjuvant treatment with imatinib. A. 18 F-FDG PET/TC showed a focal accumulation within the lesion in the right anterolateral wall of the lower third of the rectum before neoadjuvant treatment. B. 18 F-FDG PET/TC without pathological uptake after neoadjuvant treatment. Fig. 2. Pathological anatomy after neoadjuvant treatment. A. The rectal wall with submucous and intramuscular neoplasia consisting mainly of fibro-hyaline stroma with focal calcifications (arrow) and the remains of a viable GIST consisting of spindle cells (arrowhead) (H-E 2x). B. Viable tumor cells (H-E 4x). C. Weak cytoplasmic and paranuclear positivity for CD-117 (10x). D. Intense cytoplasmic positivity for DOG-1 (10x). A B A C B D