Oxygen saturation imaging endoscopy is a system that maps oxygen saturation (StO 2 ) in real time using endoscopy noninvasively. This study aimed to objectively evaluate StO 2 in colorectal polyps using oxygen saturation imaging endoscopy. We examined 133 colorectal lesions, including 78 adenomas (ADs), 35 hyperplastic polyps (HPs), and 20 sessile serrated lesions (SSLs). Prior to endoscopic resection, the StO 2 of each lesion was assessed using the oxygen saturation imaging. Five regions of interest were randomly selected from the lesion and surrounding mucosa. We calculated the average StO 2 measured at five sample points within each region of interest and then calculated the StO 2 difference between the lesion and surrounding mucosa. Furthermore, immunohistochemistry for hypoxia-inducible factor 1-alpha (HIF1α) was performed. In all groups, the mean StO 2 of the lesions was significantly lower than that of the surrounding mucosa (ADs, P < 0.001; HPs, P = 0.005; SSLs, P < 0.049). Lesions from patients with ADs revealed significantly greater StO 2 difference values between the lesion and surrounding mucosa than those from patients with HPs and SSLs (ADs vs. HPs, P < 0.001; ADs vs. SSLs, P = 0.011), although there was no difference between the values for HPs and SSLs. Immunohistochemically, HIF1α expression was 39.7% in ADs, which was significantly higher than in HPs (0.0%, P < 0.001) and SSLs (10.0%, P = 0.016). In ADs, there was a significant inverse correlation between StO 2 value and HIF1α expression ( P < 0.001). StO 2 was significantly lower in ADs than in HPs, SSLs, and the surrounding mucosa, suggesting that ADs are more hypoxic than other polyps. Assessment of mucosal StO₂ using oxygen saturation imaging endoscopy might play an important role in distinguishing biologically aggressive colorectal neoplastic lesions.
Murakami et al. (Mon,) studied this question.