Background: Near-infrared fluorescence imaging using intravenously administered indocyanine green (ICG) improves colorectal liver metastases (CRLM) surgery by enhancing lesion detection and real-time tumor margin assessment. However, ICG accumulates in hepatocytes around CRLM with high variance between patients. This study evaluates the effects of tumor and patient characteristics on ICG accumulation using a standardized imaging and analysis workflow.
Methods: This single-center study included patients with CRLM who received 10 mg of ICG intravenously 24 h before surgery. Resected lesions were sliced in 5-10-mm-thick sections and immediately imaged for standardized fluorescence analysis. Fluorescence parameters were compared based on chemotherapy treatment, tumor response, tumor size and superficiality, and degree of steatosis. Associations between the patient and tumor characteristics and fluorescence parameters were determined while correcting for confounders.
Results: Thirty-two lesions from 32 patients were analyzed. Lesions from chemotherapy-pretreated patients exhibited a lower mean signal fluorescence intensity (MSFI, 0.23 vs. 0.65 a.u.; p = 0.002) and signal-to-background ratio (SBR, 2.28 vs. 6.08; p < 0.001) than lesions from patients without pretreatment. Tumor size correlated positively with MSFI (p = 0.003), SBR (p = 0.02), and maximum intensity (p < 0.001). After correcting for the other characteristics, chemotherapy showed statistically significant association with the fluorescence parameters. The tumor superficiality, degree of steatosis, and response to chemotherapy had no statistically significant associations with the fluorescence parameters.
Conclusion: Neoadjuvant chemotherapy significantly lowers ICG accumulation around CRLM resulting in suboptimal contrast. To optimize fluorescence-guided surgery protocols for chemotherapy-pretreated patients, future research should focus on adjusting ICG dose and timing and exploring specific fluorescence tumor-targeting imaging agents.
