Diagnostic performance of 18F-fluorodeoxyglucose-PET/MRI versus MRI alone in the diagnosis of pelvic recurrence of rectal cancer

Purpose To compare the diagnostic performance of 18F-fluorodeoxyglucose-PET/MRI and MRI in the diagnosis of pelvic recurrence of rectal cancer. Methods All PET/MRIs of patients in the follow-up of rectal cancer performed between 2011 and 2018 at our institution were retrospectively reviewed. Recurrence was confirmed/excluded either by histopathology or imaging follow-up (> 4 months). Four groups of readers (groups 1/2: one radiologist each, groups 3/4: one radiologist/one nuclear medicine physician) independently interpreted MRI and PET/MRI. The likelihood of recurrence was scored on a 5-point-scale. Inter-reader agreement, sensitivity, specificity, PPV/NPV and accuracy were assessed. ROC curve analyses were performed. Results Fourty-one PET/MRIs of 40 patients (mean 61 years ± 10.9; 11 women, 29 men) were included. Sensitivity of PET/MRI in detecting recurrence was 94%, specificity 88%, PPV/NPV 97% and 78%, accuracy 93%. Sensitivity of MRI was 88%, specificity 75%, PPV/NPV 94% and 60%, accuracy 85%. ROC curve analyses showed an AUC of 0.97 for PET/MRI and 0.92 for MRI, but the difference was not statistically significant (p = 0.116). On MRI more cases were scored as equivocal (12% versus 5%). Inter-reader agreement was substantial for PET/MRI and MRI (0.723 and 0.656, respectively). Conclusion 18F-FDG-PET/MRI and MRI are accurate in the diagnosis of locally recurrent rectal cancer. Sensitivity, specificity, PPV, NPV and accuracy are comparable for both modalities, but PET/MRI increases readers’ confidence levels and reduces the number of equivocal cases. Graphic abstract

Clinical Reality and Treatment for Local Recurrence of Rectal Cancer: A Single-Center Retrospective Study

Background and Objectives: Despite advances in treatment, local recurrence remains a great concern in patients with rectal cancer. The aim of this study was to investigate the incidence and risk factors of local recurrence of rectal cancer in our single center over a 7-year-period. Materials and Methods: Patients with stage I-III rectal cancer were treated with curative intent. The necessity for radiotherapy and chemotherapy was determined before surgery and/or postoperative histopathological results. Results: Of 365 rectal cancer patients, 76 (20.8%) developed recurrent disease. In total, 27 (7.4%) patients presented with a local tumor recurrence (isolated in 40.7% of cases). Radiotherapy was performed in 296 (81.1%) patients. The most often used schema was 5 × 5 Gy followed by immediate surgery (n = 214, 58.6%). Local recurrence occurred less frequently in patients treated with 5 × 5 Gy radiotherapy followed by surgery (n = 9, 4%). Surgical procedures of relapses were performed in 12 patients, six of whom were operated with radical intent. Only two (7.4%) patients lived more than 5 years after local recurrence treatment. The incidence of local recurrence was associated with primary tumor distal location and worse prognosis. The median overall survival of patients after local recurrence treatment was 19 months. Conclusions: Individualized rectal cancer patient selection and systematic treatment algorithms should be used clinical practice to minimize likelihood of relapse. 5 × 5 Gy radiotherapy followed by immediate surgery allows good local control in resectable cT2N+/cT3N0 patients. Radical resection of isolated local recurrence offers the best chances of cure.