THE ROLE OF PROBE-BASED CONFOCAL ENDOMICROSCOPY (PCLE) IN THE DIAGNOSIS OF SUSTAINED CLINICAL COMPLETE RESPONSE UNDER WATCH-AND-WAIT STRATEGY AFTER NEOADJUVANT CHEMORADIOTHERAPY FOR LOCALLY ADVANCED RECTAL ADENOCARCINOMA
Adriana V. Safatle-Ribeiro*, John Lata, Marina Tucci Gammaro Baldavira Ferreira, Marcelo M. Flor, Caio Perez, Elisa R. Baba, Luciano H. Lenz, Bruno Da Costa Martins, Fabio S. Kawaguti, Gustavo A. De Paulo, Marcelo S. De Lima, Renata N. Moura, Caterina Pennacchi, Carla Gusmon, Sebastian Geiger, Ricardo Uemura, Caio Sergio R. Nahas, Carlos F. Marques, Antonio R. Imperiale, Guilherme C. Cotti, Ulysses Ribeiro, Fauze Maluf-Filho, Sergio C. Nahas
Universidade de Sao Paulo, Sao Paulo, São Paulo, Brazil
Background: Multimodal treatment with neoadjuvant chemoradiotherapy (nCRxt) followed by radical surgery represents the best approach for locally advanced rectal adenocarcinoma. Watch-and-wait strategy has been increasingly accepted for patients with clinical complete response (cCR), which favor organ preservation. Close follow-up is essential to the early detection of local regrowth that may occur more frequently in the first 24 months. Probe-based confocal endomicroscopy (pCLE) is a real time in vivo diagnostic method that allows acquisition of optical biopsies with 1000 times magnification. It was previously demonstrated that pCLE scoring using the combination of epithelial and vascular features might improve the diagnostic accuracy of cCR (Safatle-Ribeiro et al., J Gastrointest Surg 2021;25:357-68). Aim: To validate the pCLE scoring in the assessment of patients with cCR after nCRxt for advanced rectal adenocarcinoma. Methods: Digital rectal examination, pelvic magnetic resonance imaging (MRI) and pCLE were performed in 43 patients with cCR, who presented either a scar (N = 33; 76.7%) or a small ulcer with no signs of malignancy, and/or negative biopsy histology (N = 10; 23.3%). According to pCLE scoring, patients were classified as 0-1 point (low chance of having residual neoplasia), or 2-6 points (high chance of having a residual neoplasia). The time of follow-up varied from 5 to 51 months. Results: Twenty-five (58.1%) patients were men, and the mean age was 58.4 years. Sixteen patients had previous tumor lesions located at middle rectum and 27 patients at distal rectum. During the follow-up, 9/43 (20.9%) patients presented local regrowth and underwent salvage surgery. pCLE correctly diagnosed 7 of them (two patients presented recurrence after 12 and 24 months), and MRI 6 of them. MRI overestimated 19 patients as positive, who had no signs of regrowth. There was an association between pCLE diagnosis and final histological report (for patients who underwent surgical resection) or final diagnosis at the latest follow-up (p < 0.0001), while this association was not observed with MRI (p = 0.71). pCLE sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 77.8%, 94.1%, 77.8%, 94.1% and 90.7%, respectively. MRI sensitivity, specificity, positive predictive value, negative predictive value, and accuracy were 66.7%, 44.1%, 24%, 83.3% and 48.8%. Conclusions: 1. For patients under watch-and-wait strategy, pCLE scoring based on epithelial and vascular features improve the diagnosis of sustained cCR and might be recommended during follow-up; 2. pCLE scoring might add some valuable contribution for identifying local regrowth.
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