Platelet RNA enables accurate detection of ovarian cancer: an intercontinental, biomarker identification study

Abstract

Platelets are reprogrammed by cancer via a process called education, which favors cancer development. The transcriptional profile of tumor-educated platelets (TEPs) is skewed and therefore practicable for cancer detection. This intercontinental, hospital-based, diagnostic study included 761 treatment-naïve inpatients with histologically confirmed adnexal masses and 167 healthy controls from nine medical centers (China, n = 3; Netherlands, n = 5; Poland, n = 1) between September 2016 and May 2019. The main outcomes were the performance of TEPs and their combination with CA125 in two Chinese (VC1 and VC2) and the European (VC3) validation cohorts collectively and independently. Exploratory outcome was the value of TEPs in public pan-cancer platelet transcriptome datasets. The AUCs for TEPs in the combined validation cohort, VC1, VC2, and VC3 were 0.918 (95% CI 0.889-0.948), 0.923 (0.855-0.990), 0.918 (0.872-0.963), and 0.887 (0.813-0.960), respectively. Combination of TEPs and CA125 demonstrated an AUC of 0.922 (0.889-0.955) in the combined validation cohort; 0.955 (0.912-0.997) in VC1; 0.939 (0.901-0.977) in VC2; 0.917 (0.824-1.000) in VC3. For subgroup analysis, TEPs exhibited an AUC of 0.858, 0.859, and 0.920 to detect early-stage, borderline, non-epithelial diseases and 0.899 to discriminate ovarian cancer from endometriosis. TEPs had robustness, compatibility, and universality for preoperative diagnosis of ovarian cancer since it withstood validations in populations of different ethnicities, heterogeneous histological subtypes, and early-stage ovarian cancer. However, these observations warrant prospective validations in a larger population before clinical utilities.

Keywords: liquid biopsy; ovarian cancer; preoperative diagnosis; tumor-educated platelets.

Figure 1.

Differences in platelets between OC and non-OC patients. (A) The real-world study of the association between platelet counts and ovarian cancer. These individuals were composed of 1,301 patients with ovarian cancer and 8,667 individuals without cancer Boxplots represent median value, with lower and upper hinges corresponding to the 25th and 75th percentiles, and lower and upper whiskers extending from the hinge to the smallest and largest value at most 1.5× interquartile range of the hinge, respectively. Two-sided student’s t-test. (B) Heatmap of unsupervised clustering and (C) platelet mRNA profiles of patients with ovarian cancer and non-OC individuals in discovery cohort. We found that mRNA sequencing can well discriminate patients with OC from non-OC individuals. OC, ovarian cancer.

Figure 2.

Study design and patient enrollment. Unqualified samples were those with low quality (RNA integrity number < 7) or quantity (<10 pg) of total RNA. OC, ovarian cancer. BAM, benign adnexal mass. TEPOC, tumor-educated platelet-derived gene panel of ovarian cancer. TC, training cohort. DC, discovery cohort. VC1, validation cohort 1. VC2, validation cohort 2. VC3, validation cohort 3.

Figure 3.

Performance of TEPOC and its combination with CA125 in validation cohorts and ovarian cancer subgroups. The performance of CA125 (green line), TEPOC (red line), and TEPOC+CA125 (blue line) to detect ovarian cancer were estimated by plotting receiver operating characteristic curves in (A) three validation cohorts combined, (B) validation cohort 1, (C) validation cohort 2, (D) validation cohort 3. Abbreviations: AUC, area under the curve; TEPOC, tumor-educated platelet-derived gene panel of ovarian cancer; CA125, cancer antigen 125; TEPOC+CA125, a combined diagnosis of TEPOC and CA125; BAM, benign adnexal mass.

Figure 4.

Performance of TEPOC and its combination with CA125 in ovarian cancer subgroups. (A) Endometriosis cohort (endometriosis n = 37 vs. ovarian cancer n = 127), (B) borderline cohort (borderline ovarian tumors n = 43 vs. BAM n = 107), (C) early-stage cohort (early-stage ovarian cancer n = 41 vs. BAM n = 107), and (D) non-epithelial cohort (non-epithelial malignancies n = 23 vs. BAM n = 93). Abbreviations: AUC, area under the curve; TEPOC, tumor-educated platelet-derived gene panel of ovarian cancer; CA125, cancer antigen 125; TEPOC+CA125, a combined diagnosis of TEPOC and CA125; BAM, benign adnexal mass.