Tumor-derived extracellular vesicles in blood of metastatic breast, colorectal, prostate, and non-small cell lung cancer patients associate with worse survival

Circulating Tumor Cell (CTC) counts, as determined by the CellSearch^® system, associate with poor overall survival (OS) in castration-resistant prostate cancer (CRPC), breast, colorectal and non-small cell lung (NSCLC) cancer patients. The cut-offs used to discriminate between patients with favorable and unfavorable prognoses are 5 CTCs / 7.5 mL of blood for breast and CRPC, 3 for colorectal and 1 for NSCLC. The low numbers of CTCs frequently limit the accurate discrimination of patients into favorable or unfavorable prognosis groups. We previously reported the presence of CK+, DNA-, CD45- tumor-derived extracellular vesicles (tdEVs) in ~20x higher frequencies in CRPC patients and showed their equivalence to CTC counts in predicting clinical outcome. In this study, we explored the presence of tdEVs in the blood of metastatic CRPC, breast, colorectal, and NSCLC patients, determined the association of tdEVs with OS and whether they aid in stratifying patients with favorable CTC counts. Digitally stored CellSearch^® system images obtained from previously reported studies from 190 CRPC, 450 colorectal, 179 breast and 117 NSCLC patients before the initiation of a new treatment were used to enumerate tdEVs automatically using the open-source ACCEPT software. tdEV counts highly correlated with CTC counts in all cancer types (Spearman’s Rho tests p<0.001) and were present at 0-280-fold (Mean 20, SD 25) higher frequencies. A cut-off tdEV value of 23 (median +2SD of 93 healthy donors) was used to dichotomize patients into favorable and unfavorable groups. Kaplan-Meier analyses showed associations of CTCs and tdEVs with OS with hazard ratios (HRs) of 2.4 & 2.1 in CRPC, 2.7 & 2.1 in breast, 2.3 & 2.0 in colorectal and 1.6 & 2.0 in NSCLC, respectively. 52% of the 43% CRPC patients with favorable CTC counts had elevated tdEVs; 53% of the 50% breast cancer patients with favorable CTC counts had elevated tdEVs; 46% of the 72% colorectal cancer patients with favorable CTC counts had elevated tdEVs and 3% of the 75% NSCLC patients with favorable CTC counts had unfavorable tdEVs. CRPC, colorectal and breast cancer patients with favorable CTC counts could be further stratified using tdEV counts (log-rank tests p < 0.05). CTC and tdEV counts equally predict OS n the different cancer types studied. Use of tdEVs in patients with favorable CTC counts can further stratify patients and thereby contribute to clinical decision making. Funded by the NWO Applied and Engineering Sciences Cancer-ID project #14190, the EUFP7 CTCTrap project #305341 and the EU IMI CANCER-ID project # 115749-1.