Background: Digital image analysis offers advantages over traditional pathologist visual scoring of immunohistochemistry, although few studies examining the correlation and reproducibility of these methods have been performed in prostate cancer. We evaluated the correlation between digital image analysis (continuous variable data) and pathologist visual scoring (quasi-continuous variable data), reproducibility of each method, and association of digital image analysis methods with outcomes using prostate cancer tissue microarrays (TMAs) stained for estrogen receptor-β2 (ERβ2). Methods: Prostate cancer TMAs were digitized and evaluated by pathologist visual scoring versus digital image analysis for ERβ2 staining within tumor epithelium. Two independent analysis runs were performed to evaluate reproducibility. Image analysis data were evaluated for associations with recurrence-free survival and disease specific survival following radical prostatectomy. Results: We observed weak/moderate Spearman correlation between digital image analysis and pathologist visual scores of tumor nuclei (Analysis Run A: 0.42, Analysis Run B: 0.41), and moderate/strong correlation between digital image analysis and pathologist visual scores of tumor cytoplasm (Analysis Run A: 0.70, Analysis Run B: 0.69). For the reproducibility analysis, there was high Spearman correlation between pathologist visual scores generated for individual TMA spots across Analysis Runs A and B (Nuclei: 0.84, Cytoplasm: 0.83), and very high correlation between digital image analysis for individual TMA spots across Analysis Runs A and B (Nuclei: 0.99, Cytoplasm: 0.99). Further, ERβ2 staining was significantly associated with increased risk of prostate cancer-specific mortality (PCSM) when quantified by cytoplasmic digital image analysis (HR 2.16, 95 % CI 1.02-4.57, p=0.045), nuclear image analysis (HR 2.67, 95 % CI 1.20-5.96, p=0.016), and total malignant epithelial area analysis (HR 5.10, 95 % CI 1.70-15.34, p=0.004). After adjusting for clinicopathologic factors, only total malignant epithelial area ERβ2 staining was significantly associated with PCSM (HR 4.08, 95 % CI 1.37-12.15, p=0.012). Conclusions: Digital methods of immunohistochemical quantification are more reproducible than pathologist visual scoring in prostate cancer, suggesting that digital methods are preferable and especially warranted for studies involving large sample sizes.
Bibliographical noteFunding Information:
This study utilized services from NWBioSpecimen which was supported by National Cancer Institute grant P30 CA015704 (F. Appelbaum), Life Sciences Discovery Fund (LSDF) grant Washington Phenotyped Biospecimen Resource (J. Slattery), LSDF grant Consortium Biospecimen Program (P. Porter), Fred Hutchinson Cancer Research Center, the University of Washington School of Medicine, and the University of Washington Department of Pathology. The work was also supported by grants R01-CA056678, R01-CA092579, R03-CA137799, and P50-CA097186 (J. Stanford) from the National Cancer Institute, with additional support from the Fred Hutchinson Cancer Research Center, the Prostate Cancer Foundation, and the Institute for Prostate Cancer Research.
© 2016 The Author(s).
- Digital pathology
- Estrogen receptor β2
- Prostate cancer