Sumito Sato1,2, Hirotada Kagoshima3, Manabu Shiozawa2, Suguru Nukada2, Kenta Iguchi2, Yo Mikayama2, Takashi Oshima2, Masakatsu Numata4, Hiroshi Tamagawa4, Yasushi Rino4, Munetaka Masuda4, Kuniya Tanaka1

1Department of Gastroenterological and General Surgery, Showa University Fujigaoka Hospital, Yokohama, 227-8501, Japan, 2Department of Gastrointestinal Surgery, Kanagawa Cancer Center, Yokohama, 241-8515, Japan, 3Rigaku Corporation, Tokyo 151-0051, Japan, 4Department of Surgery, Yokohama City University, Yokohama, 236-0004, Japan

Background/Aims: Although minimally invasive surgery for colorectal cancer, whether performed as standard laparoscopic or robotic surgery, has been established as an oncologically safe procedure, postoperative urinary dysfunction and sexual dysfunction remain matters of concern, even when so-called nerve-sparing surgery is performed. We have hypothesized that Raman spectroscopy can be used intraoperatively as a non-invasive label-free means of objective identification of the pelvic nerves, and we conducted a preliminary study by applying a newly developed handheld Raman spectrometer to surgical specimens.

Methods: Samples of nervous tissue, colon cancer tissue, and tissues from surrounding pelvic organs were obtained from 25 patients undergoing colectomy. Raman spectra were obtained by irradiation with the Progeny

Results: We detected characteristic differences in the spectra at 1309 cm-1, 1442 cm-1, and 1658 cm-1. A significant difference was detected at 1442 cm-1, and accuracy of the modality for identification of nervous tissue was 75%. Discrimination between nervous tissue and cancer tissue based on 4 principal components yielded sensitivity, specificity, and accuracy of 100%, 85%, and 90%, respectively.

Conclusion: Raman spectroscopy holds promise for non-invasive intraoperative recognition of nervous tissue. We expect the modality to become a powerful clinical tool, compensating for the lack of tactile feedback intrinsic to minimally invasive colectomy and thus thwarting the risk of postoperative urinary and/or sexual dysfunction.

Keywords: Colorectal cancer, Raman spectroscopy, Minimally invasive surgery, Postoperative dysfunction, Autonomic nerve