Detection of Lymph Node Metastases in Human Colorectal Cancer by Using 5-Aminolevulinic Acid-Induced Protoporphyrin IX Fluorescence with Spectral Unmixing

Kenichi Harada,Noriaki Koizumi,Ping Dai,Takeo Minamikawa,Akio Yanagisawa,Yasutoshi Murayama,Masayoshi Nakanishi,Masatomo Beika,Yoshinori Harada,Yoshiaki Kuriu,Tetsuro Takamatsu,Eigo Otsuji,Koji Inoue,Yoshihisa Yamaoka

doi:10.3390/ijms141123140

Kenichi Harada, Noriaki Koizumi + Show 12 more

Open Access

https://doi.org/10.3390/ijms141123140

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Abstract

Accurate evaluation of metastatic lymph nodes (LNs) is indispensable for adequate treatment of colorectal cancer (CRC) patients. Here, we demonstrate detection of metastases of human CRC in removed fresh LNs using 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence. A spectral unmixing method was employed to reduce the overlap of collagen autofluorescence on PpIX fluorescence. A total of 17 surgery patients with advanced CRC were included in this study. After 5-ALA at a dose of 15 mg/kg of body weight was applied orally 2 h prior to surgery, 87 LNs were subjected to spectral fluorescence imaging and histopathological diagnosis, and statistical analysis was performed. No apparent side effect was observed to be associated with 5-ALA administration. The spectral unmixing fluorescence intensity of PpIX in metastatic LNs was 10.2-fold greater than that in nonmetastaic LNs. The receiver-operating-characteristic (ROC) analysis showed that the area under the curve (AUC) was calculated as 0.95. Our results show the potential of 5-ALA-induced PpIX fluorescence processed by spectral unmixing for detecting metastases in excised fresh LNs from patients with CRC, suggesting that this rapid and feasible method is applicable to gross evaluation of resected LN samples in pathology laboratories.

Highlights

Colorectal cancer (CRC) is the second most common cause of cancer mortality and the most frequent cancer in many countries
We demonstrated that 5-aminolevulinic acid (ALA)-induced protoporphyrin IX (PpIX) fluorescence signal processed by using the spectral unmixing method is useful for the detection of colorectal cancer (CRC) metastases in excised fresh human
As far as we know, this is the first report on the application of 5-ALA-induced PpIX fluorescence to detect metastatic lymph nodes (LNs) in human CRCs

Summary

Introduction

Colorectal cancer (CRC) is the second most common cause of cancer mortality and the most frequent cancer in many countries. Lymph node (LN) metastasis is a feature associated with advanced CRC [2,3]. There is mounting evidence from large population-based studies that the number of LNs examined by pathologists has a significant impact on survival in CRC. Among detection methods for LN metastases, histopathological analysis of LNs is regarded as a gold standard. Routine histopathological analysis of LNs has been shown to have a limited sensitivity for the detection of CRC metastases [9,10,11,12]; in general, only a few hematoxylin-eosin (H & E)-stain slides from the excised LNs are analyzed without macroscopic identification in a routine work. It is reported that there is a significant risk of underestimating nodal metastasis in the routine pathological examinations [13,14]. A new method for detecting metastatic foci of removed

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