Desley van Zoggel

PET/CT response after induction chemotherapy 123 CHAPTER 7 Methods Patients The data of consecutive LRRC patients treated at the Catharina Hospital (CZE), a national tertiary referral centre for LRRC in the Netherlands, were prospectively collected in a database and retrospectively reviewed. For this study, all LRRC patients who underwent induction chemotherapy and chemo(re)irradiation followed by resection with curative intent between January 2010 and July 2020 were selected. Induction chemotherapy consisted of four cycles of CAPOX (capecitabine and oxaliplatin) or FOLFOX (leucovorin, fluorouracil and oxaliplatin). Full course chemoradiation in radiotherapy naive patients (n = 23) consisted of 25 fractions of 2 Gy with concomitant capecitabine 825 mg/m2 twice daily; chemo(re)irradiation in radiotherapy non-naive patients (n = 83) consisted of 15 fractions of 2 Gy with concomitant capecitabine 825 mg/m2 twice daily. Full course chemoradiation and chemo(re)irradiation were delivered to 22 and 84 patients, respectively. All patients had at least a pretreatment PET/CT and a post-treatment PET/CT prior to surgery. Patients with PET/CT images that could not be revised were excluded, as were patients who underwent palliative treatment. Further details regarding the patient selection are shown in Figure 1. This study was approved by the local medical ethics board (Medical Research Ethics Committees United— Nieuwegein, registration number W19.031); individual informed consent was not required. PET/CT imaging For non-referred patients, whole-body images from the skull base to the mid-thigh were obtained using PET/CT (Discovery 710, GE Healthcare) in accordance with accepted institutional procedures. Image acquisition was started approximately 60 min after the tracer injection. For referred patients, pretreatment whole-body PET/ CT images were obtained from the referring hospital. All patients underwent posttreatment PET/CT at our institution, once again in accordance with the accepted institutional procedures. Qualitative visual analysis was performed using dedicated commercial software (Philips iPortal, Eindhoven, The Netherlands). Visual analysis was performed according to the accepted guidelines.11 Complete metabolic response (CMR) was defined as no visible activity at the initial tumour site, or activity at the initial tumour site not exceeding adjacent physiological bowel activity in the case of luminal recurrence. No response (NR) was defined as unchanged or increased activity,