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BERKELEY, CA (UroToday.com) - Metastatic castration resistant prostate cancer (mCRPC) is often difficult to evaluate using conventional assessments, which poses challenges for therapeutic decision making. The presence of tumor cells in the peripheral circulation (i.e., circulating tumor cells, or CTCs) appears to be an intrinsic property of the disease. Multiple studies have shown that information from enumeration of CTCs in mCRPC is relevant to survival, response to therapy, as well as the biology of the disease. In mCRPC, the presence of CTCs in the peripheral circulation is highly specific for cancer and elevated levels of CTCs signal reduced survival time. Furthermore, the kinetics of response of CTC levels to chemotherapy are rapid. One can take advantage of these properties of CTCs through serial measurements from a simple blood sample to add information to that available from conventional assessments, including imaging and serum PSA levels. The case described in this paper describes a case of mCRPC where serum PSA levels were not informative in the context of conflicting information from imaging and clinical symptoms, and CTC information proved to be useful.

An example of CTC utility from this case is presented here. Following progression on complete androgen blockade, as measured by elevated PSA, elevated CTC counts, and pain, the patient was enrolled in a study in which he received docetaxel and bevacizumab. After 2 cycles of therapy, imaging and serum PSA both suggested efficacy, while CTC counts remained elevated, suggesting progression. Three months later (11 months post-Dx), repeat assessments again showed that serum PSA was very low, while imaging and patient reports of pain were indicative of progression (Table 1). Evaluation of CTC levels demonstrated that CTCs were still well above the 5 per 7.5 mL poor prognosis cut-off. This element of information provided sufficient confidence that the patient was progressing on docetaxel and to switch him to cyclophosphamide. The patient responded to cyclophosphamide as measured at 13 months post-diagnosis: imaging demonstrated a partial response, the patient reported lessened pain, and his CTC count dropped to zero, while his serum PSA level remained low (Table 1). Additional cycles of disease measurement, decision making, and therapy are described, and the impact of CTC enumeration on management of this patient is discussed.


Table 1: Assessments on docetaxel

Time Point Post-Dx

Therapy

CT Imaging

Serum PSA

ng/mL

Signs/symptoms

CTC Count

Per 7.5 mL

11 months

Docetaxel + Bevacizumab

PD

1.0

Worsening pain

13

13 months

Cyclophosphamide

PR

3.4

Lessened pain

0


Dx-diagnosis; CT computerized tomography; CTC-circulating tumor cells; PD-progressive disease; PR-partial response.


Written by:
Oscar Goodman, MD, PhDa and Eric R. Schuur, PhDb, c as part of Beyond the Abstract on UroToday.com. This initiative offers a method of publishing for the professional urology community. Authors are given an opportunity to expand on the circumstances, limitations etc... of their research by referencing the published abstract.

aComprehensive Cancer Centers of Nevada, Las Vegas, NV USA; bVMWA LLC, Palo Alto, CA USA; and cThe Jon Block Group, San Francisco, CA USA

Integrating circulating tumor cell data with imaging and serum prostate-specific antigen measurement for metastatic prostate cancer therapy management - Abstract

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