What To Do With Suspected Nodal Regrowth on MRI During Follow-Up in an Organ Preservation Approach for Rectal Cancer?

BACKGROUND: For nodal regrowth in patients with rectal cancer following watch-and-wait, standardized protocols on diagnostic procedures and subsequent treatment are lacking. OBJECTIVE: To evaluate the diagnosis and treatment of suspected nodal regrowth following an organ preservation approach. SETTINGS: Patients were included from national and institutional watch-and-wait databases. DESIGN: Thirty-five rectal cancer patients with suspected nodal regrowth on MRI were retrospectively identified during watch-and-wait follow-up. PATIENTS: Twenty-seven of 35 patients followed the watch-and-wait schedule after neoadjuvant (chemo) radiotherapy and 8 of 35 patients followed the watch-and-wait schedule after local excision for early rectal cancer. MAIN OUTCOME MEASURES: Diagnostic procedures, treatment, and histopathological outcome. RESULTS: The median follow-up was 34 months. The median time from the end of (chemo)radiotherapy or local excision to the first detection of suspected nodal regrowth on MRI following watch-and-wait was 9 and 10 months. After the first detection, 17 of 35 patients underwent immediate treatment without further diagnostics, of whom 7 also had luminal regrowth. In 18 of 35 patients, additional diagnostic procedures were performed. In 4 of 18 patients, PET-CT or endorectal ultrasound-guided biopsy was performed, and treatment was initiated on the basis of increased nodal regrowth suspicion. In 14 of 18 patients, MRI was repeated after 8 to 12 weeks: growth of suspected lymph nodes was the most decisive factor to proceed to treatment. In 8 patients, repeated MRI was combined with PET-CT and/ or endorectal ultrasound-guided biopsy: in half of them, it contributed to treatment initiation. In total, 34 of 35 patients were treated: 9 received (re-)irradiation and 33 underwent total mesorectal excision. In 27 of 33 patients, nodal regrowth was pathologically confirmed in the total mesorectal excision-resection specimen; 5 of 6 patients without nodal involvement had pathologically confirmed luminal regrowth. LIMITATIONS: Highly selected study population. CONCLUSIONS: During watch-and-wait follow-up of patients with rectal cancer in an organ preservation strategy, MRI plays an important role in the diagnosis of nodal regrowth. Repeated MRI after an interval can be helpful in making treatment decisions, and the role of PET-CT and endorectal ultrasound-guided biopsy appears limited.