Organ preservation appears oncologically safe for selected rectal cancer patients with a cCR or near cCR after neoadjuvant chemoradiation when applying strict selection criteria and frequent follow-up, including endoscopy and MRI. The low colostomy rate and the good long-term functional outcome warrant discussing this option with the patient as an alternative to major surgery.

BackgroundThe response to chemoradiotherapy (CRT) for rectal cancer can be assessed by clinical examination, consisting of digital rectal examination (DRE) and endoscopy, and by MRI. A high accuracy is required to select complete response (CR) for organ-preserving treatment. The aim of this study was to evaluate the value of clinical examination (endoscopy with or without biopsy and DRE), T2W-MRI, and diffusion-weighted MRI (DWI) for the detection of CR after CRT.MethodsThis prospective cohort study in a university hospital recruited 50 patients who underwent clinical assessment (DRE, endoscopy with or without biopsy), T2W-MRI, and DWI at 6–8 weeks after CRT. Confidence levels were used to score the likelihood of CR. The reference standard was histopathology or recurrence-free interval of >12 months in cases of wait-and-see approaches. Diagnostic performance was calculated by area under the receiver operator characteristics curve, with corresponding sensitivities and specificities. Strategies were assessed and compared by use of likelihood ratios.ResultsSeventeen (34 %) of 50 patients had a CR. Areas under the curve were 0.88 (0.78–1.00) for clinical assessment and 0.79 (0.66–0.92) for T2W-MRI and DWI. Combining the modalities led to a posttest probability for predicting a CR of 98 %. Conversely, when all modalities indicated residual tumor, 15 % of patients still experienced CR.ConclusionsClinical assessment after CRT is the single most accurate modality for identification of CR after CRT. Addition of MRI with DWI further improves the diagnostic performance, and the combination can be recommended as the optimal strategy for a safe and accurate selection of CR after CRT.

After a successful watch-and-wait approach, the quality of life was better than after chemoradiation and surgery on several domains. However, chemoradiation therapy on its own is not without long-term side effects, because one-third of the watch-and-wait patients experienced major low anterior resection syndrome symptoms, compared with 66.7% of the patients in the total mesorectal excision group. See Video Abstract at http://links.lww.com/DCR/A395.

Previously established DWI volume thresholds can be reproduced with good results. Post-CRT DWI volumetry offers the best results for the detection of patients with a complete response after CRT with an area under the curve of 0.92, sensitivity of 70%, and specificity of 98%.