Very small nuclear circulating tumor cell (vsnCTC) as a putative biomarker for visceral metastasis in metastatic castration-resistant prostate cancer (mCRPC).

Abstract

64 Background: Patients with metastatic castration-resistant prostate cancer (mCRPC) who develop visceral metastasis (VM) have a poorer clinical outcome in comparison to those without VM. Their clinical course is aggressive and culminates in organ failure as this process is often discovered late in the disease course. There are no existing tests that identify men at risk for VM. Our team has identified an association between the presence of very small nuclear circulating tumor cells (vsnCTCs) and VM. We hypothesized that vsnCTC that can predict the development of VM and monitor the response to anticancer treatment. Methods: In our database we identified mCRPC patients who had progressed through next generation hormonal maneuvers such as abiraterone, enzalutamide, or an equivalent drug. Serial blood specimens were used for vsnCTC enumeration using published methods. The vsnCTC counts were related to the presence and development of VM as well as the response to anticancer treatment. Results: Blood specimens were identified from 28 patients who met the eligibility criteria; 16/28 patients presented with VM and 12/28 had bone-only disease at their first CTC enumeration. Five out of 12 non-VM patients developed VM during follow-up, and vsnCTCs were detected 86-196 days prior to radiographic detection of VM (true positive); 3/12 had vsnCTCs detected but no VM was found by the time of analysis (false positive). None of the vsnCTC(-) patients developed VM. vsnCTCs were detected in 21/21 VM patients compared to 3/12 non-VM patients. Reduction of vsnCTC count occurred at initiation of anticancer treatment; transition from vsnCTC(-) to vsnCTC(+) was seen prior to progression under the treatment. Conclusions: vsnCTC is associated with the presence of VM and is a potential biomarker for predicting the development of VM and monitoring the treatment response in mCRPC. Transition from vsnCTC(-) to vsnCTC(+) was associated with the development of VM and progression under the treatment.