Assessment of Residual or Resected Disappearing Liver Metastases After Chemotherapy

Objective: To prospectively assess the incidence of residual disease in disappearing liver metastases (DLM) and evaluate associated oncologic outcomes. Summary Background Data: DLM are colorectal liver metastases that become undetectable on imaging after chemotherapy. Although DLM are increasingly observed with modern systemic therapy and imaging, their clinical significance and appropriate management remain unclear. Methods: A single-center, observational cohort study conducted at Cancer Institute Hospital, Tokyo, from April 2020 to March 2024. DLM was defined as liver metastases detectable by contrast-enhanced CT or gadolinium-ethoxybenzyl-diethylenetriamine penta acetic acid-enhanced MRI before chemotherapy, but undetectable on both modalities afterward. Intraoperatively identified DLM were resected and pathologically examined. Unresected DLM were monitored by postoperative imaging. Results: A total of 46 patients with 172 DLM were included. Of the 80 resected DLM, six (7.5%) contained pathological residual disease. Of 91 unresected DLM, 10 (11.0%) showed clinically residual disease. The 6- and 12-month cumulative recurrence rates at the DLM site in unresected DLM were 2.2% and 7.7%, respectively. In total, 9.3% (95% confidence intervals: 5.5–14.6%) of DLM were confirmed as residual disease. Twenty-six patients (56.5%) experienced recurrence: nine in the all-resected group and 17 in the unresected group. Among the latter, eight developed recurrence at the same site as their DLM site, and five underwent repeat resection. Median recurrence-free and overall survivals were 17.4 months and ‘not reached’. Conclusion: Approximately 10% of DLM harbored residual disease. These findings support selective resection strategies based on intraoperative findings and highlight the importance of precise imaging and postoperative surveillance.