Real-time detection of hepatic micrometastases from pancreatic cancer by intraoperative fluorescence imaging: preliminary results of a prospective study

Abstract

Background: Recently, a highly sensitive fluorescent imaging technique was developed for the real-time identification of hepatic tumors. The authors applied this procedure for the intraoperative detection of radiographically occult hepatic micrometastases from pancreatic cancer.

Methods: Forty-nine consecutive patients with pancreatic cancer who underwent surgical intervention were examined. Preoperative clinical images had not revealed any hepatic metastases. On the day before surgery, indocyanine green was injected intravenously. During the operation, the liver was observed with a near-infrared camera system, and abnormal fluorescent foci were examined by frozen-section histology. The patients with hepatic micrometastases were judged to have unresectable disease and underwent only palliative surgery followed by systemic chemotherapy using gemcitabine.

Results: Abnormal hepatic fluorescence at least 1.5 mm in greatest dimension without any apparent tumor was observed in 13 patients. Among them, histologic examination confirmed micrometastases in 8 of 49 patients (16%). All patients with hepatic micrometastases had clinical T3 or T4 disease and high serum CA19-9 levels (P = .042). On follow-up computed tomography images that were obtained within 6 months after surgery, the patients with hepatic micrometastases manifested hepatic overt metastases (7 of 8 patients; 88%) more frequently than the patients without hepatic micrometastases (4 of 41 patients; 10%; P < .001). Regardless of histologic confirmation, the positive predictive value of abnormal fluorescence for the manifestation of hepatic relapse within 6 months was 77% (10 of 13 patients), and the negative predictive value was 97% (35 of 36 patients).

Conclusions: Indocyanine green-fluorescent imaging can detect hepatic micrometastases of pancreatic cancer during surgery. The hepatic micrometastases seem to have an adverse clinical impact identical to that of evident distant metastases.