Usefulness of grayscale values measuring hypoechoic lesions for predicting prostate cancer: An experimental pilot study

Abstract

Background: To ensure reproducibility and representativeness of hypoechoic lesions in transrectal ultrasonography (TRUS), we used grayscale values and evaluated their usefulness in predicting prostate cancer (PCA).

Methods: A total of 172 patients scheduled for prostate biopsy for suspected PCA between October 2016 and May 2018 were prospectively enrolled. Patients underwent 12 core target biopsies for hypoechoic lesions in 12 areas of the prostate and two additional target biopsy cores for two hypoechoic lesions. We estimated the grayscale value of the image using a red/green/blue scoring method through a function embedded in the picture archiving and communication system. Imaging data were analyzed using estimated grayscale values.

Results: Of the 127 patients (median age = 68.5 years, median prostate-specific antigen level = 6.19 ng/mL), 67 (52.8%) had PCA. Of 1778 biopsy lesions, 327 (18.4%) were PCA lesions. No differences in the grayscale values were found between PCA and benign lesions; however, the grayscale value between 28.0 and 57.0 for hypoechoic lesions was identified as a significant factor for predicting PCA in multivariable analysis (p=0.008). Multivariable analysis indicated a grayscale value between 34.0 and 48.0 as a predicting factor for clinically significant PCA (cs-PCA: Gleason grade group ≥2) (p=0.001). The area under the curve (AUC) for predicting cs-PCA was higher for combined clinical and grayscale value parameters than for TRUS grayscale values (0.780 vs. 0.561, p<0.001).

Conclusions: Hypoechoic lesions that meet the quantitative criteria seem useful for predicting cs-PCA. The presence of hypoechoic lesions is not a predicting factor for PCA.

Keywords: Biopsy; Hypoechoic lesion; Prostate; Transrectal ultrasonography.

Fig. 1

Association of transrectal ultrasound images with grayscale values and pathology reports of the prostate biopsies. A: The grayscale value of 91.23 is pathologically categorized as noncancerous. B: The grayscale value of 25.36 is pathologically categorized as noncancerous. C: The grayscale value of 53.72 is pathologically categorized as prostate cancer with a Gleason score of 6. D: The grayscale value of 31.43 is pathologically categorized as prostate cancer with a Gleason score of 6. E: The grayscale value of 45.65 is pathologically categorized as prostate cancer with a Gleason score of 7. F: The grayscale value of 39.51 is pathologically categorized as prostate cancer with a Gleason score of 8.

Fig. 2

ROC curves of detecting PCA lesion using clinical variables and grayscale values (ranging from 28.0 to 57.0) of hypoechoic lesions. AUC of clinical variables: 0.754, AUC of grayscale value of hypoechoic lesion: 0.535, AUC of the grayscale of clinical variables plus grayscale of hypoechoic lesion: 0.755. AUC, area under the curve of receiver operator characteristic; PCA, prostate cancer; ROC, receiver operator characteristic.

Fig. 3

ROC curves of detecting cs-PCA lesion using clinical variables and grayscale values (ranging from 34.0 to 48.0) of hypoechoic lesions. AUC of clinical variables: 0.771, AUC of the grayscale value of hypoechoic lesion: 0.561, AUC of the grayscale of clinical variables plus grayscale of hypoechoic lesion: 0.780, AUC, area under the curve of receiver operator characteristic; cs-PCA, clinically significant prostate cancer; PCA, prostate cancer; ROC, receiver operator characteristic.