Risk and location of distant metastases in patients with locally advanced rectal cancer after total neoadjuvant treatment or chemoradiotherapy in the RAPIDO trial

INTRODUCTION: Although optimising rectal cancer treatment has reduced local recurrence rates, many patients develop distant metastases (DM). The current study investigated whether a total neoadjuvant treatment strategy influences the development, location, and timing of metastases in patients diagnosed with high-risk locally advanced rectal cancer included in the Rectal cancer And Pre-operative Induction therapy followed by Dedicated Operation (RAPIDO) trial. MATERIAL AND METHODS: Patients were randomly assigned to short-course radiotherapy followed by 18 weeks of CAPOX or FOLFOX4 before surgery (EXP), or long-course chemoradiotherapy with optional postoperative chemotherapy (SC-G). Assessments for metastatic disease were performed pre- and post-treatment, during surgery, and 6, 12, 24, 36, and 60 months postoperatively. From randomisation, differences in the occurrence of DM and first site of metastasis were evaluated. RESULTS: In total, 462 patients were evaluated in the EXP and 450 patients in the SC-G groups. The cumulative probability of DM at 5 years after randomisation was 23% [95% CI 19-27] and 30% [95% CI 26-35] (HR 0.72 [95% CI 0.56-0.93]; P = 0.011) in the EXP and SC-G, respectively. The median time to DM was 1.4 (EXP) and 1.3 years (SC-G). After diagnosis of DM, median survival was 2.6 years [95% CI 2.0-3.1] in the EXP and 3.2 years [95% CI 2.3-4.1] in the SC-G groups (HR 1.39 [95% CI 1.01-1.92]; P = 0.04). First occurrence of DM was most often in the lungs (60/462 [13%] EXP and 55/450 [12%] SC-G) or the liver (40/462 [9%] EXP and 69/450 [15%] SC-G). A hospital policy of postoperative chemotherapy did not influence the development of DM. CONCLUSIONS: Compared to long-course chemoradiotherapy, total neoadjuvant treatment with short-course radiotherapy and chemotherapy significantly decreased the occurrence of metastases, particularly liver metastases.