Relapse patterns, risk factors, re-resectability and survival after curative treatment for metastatic colorectal cancer (mCRC): A RAXO substudy.

3566 Background: In mCRC, metastasectomy and/or local ablative treatment (LAT) cures some. However, over 70% of the patients relapse, with liver, lung and peritoneum being the most common recurrence sites. Data on recurrence patterns and prognostic factors are mainly limited to patients with liver metastases treated before 2008. An update including patients also with multisite metastases treated up-to-date is needed. Methods: In this study, 323 patients from the RAXO-study (2012–2018) were analyzed, 312 patients had undergone R0–1 metastasectomy and 11 patients had A0–1 LAT. Three patients with postoperative death were excluded. The remaining 320 patients were prospectively followed for at least five years, with radiological imaging and blood tests every 3–6 months in the first two years and every 6–12 months thereafter. Median time to recurrence (mTTR), and overall survival (mOS) were estimated with Kaplan-Meier from the date of curative surgery/LAT for metastases known at baseline and compared using log-rank. Hazard ratios (HR) were estimated using Cox regression. Results: mTTR was 17 months (CI 95% 13–23 months) with 221 patients (69% of all) relapsing during follow-up. Totally 135 recurrences (42% of the patients at risk) occurred during the first year. During the second, third, fourth and fifth year, recurrence occurred in 48 (26%), 27 (20%), 7 (7%) and 1 (1%) patients at risk, respectively. Of patients relapsing during the first year, 65 (60%) were re-resected with numbers for subsequent years being 18 (67%), 3 (43%), 0 (0%) and 1 (33%), respectively. mTTR, mOS, and re-resectability outcomes for the most common recurrence sites are presented in the table. Regional lymph node metastasis (HR 1.4), RAS mutation (1.4), R1 resection (2.3) and treatment with LAT (2.4) were prognostic for recurrence ( p &lt; 0.05). Conclusions: Two-thirds of curatively treated mCRC patients relapse within the first four years. Curative-intent re-resection provides good OS for most sites of recurrence and should be considered when possible. Clinical trial information: NCT01531621 . Resected, n (%) mTTR, months mOS 1st resection, months Re-resection, n (%) mOS re-resected, months Non-re-resected, n (%) mOS non-re-resected, months p R0–1 resected patients 320 16 92 Recurrence at any site 221 (100%) 10 61 116 (52%) 79 105 (48%) 44 &lt; 0.01 – Lung 96 (43%) 10 64 45 (20%) 103 51 (23%) 52 &lt; 0.01 – Liver 72 (33%) 8 54 44 (20%) 77 28 (13%) 39 &lt; 0.01 – Distant lymph nodes 37 (17%) 9 56 5 (2%) 58 32 (14%) 48 0.31 – Peritoneum 23 (10%) 10 60 11 (5%) 92 12 (5%) 29 &lt; 0.01 – Local recurrence 21 (10%) 10 58 9 (4%) 58 12 (5%) 56 0.31 – Intrahepatic only 56 (25%) 9 56 41 (19%) 77 15 (7%) 38 &lt; 0.01 – Intrapulmonary only <jats:td colspan="1