An uncommon, but very aggressive form of prostate cancer is known as Neuroendocrine prostate cancer (NEPC). It is generally accepted that Circulating Tumor Cell (CTC) counts as measured by CellSearch (a method to catch and count these cells in the blood) are prognostic for most men with metastatic prostate cancer (mPC), but are not well understood in NEPC.

A group of researchers retrospectively identified men with metastatic PC and available CTC enumeration (CellSearch methodology) and compared counts/7.5 mL blood and overall survival (OS), measured from the first recorded CTC count until death or last follow up.

Entry criteria for clinical trials were used to define which men had NEPC, including histology (small cell/neuroendocrine carcinoma or adenocarcinoma with more than 50% NE staining), serum chromogranin greater than 5x ULN and/or neuron specific enolase greater than 2x ULN, and/or predominant liver/brain metastases with lack of prostate-specific antigen

[Beltran ASCO 2013, clinicaltrials.gov NCT01799278].

Frequency of detectable and unfavorable counts was tabulated and OS was compared across the groups.

Sixty one men were identified from their population: 21 NEPC with median age 73.7 and 40 men with castration-resistant prostate cancer (CRPC) with median age 73.9.

The median OS for the entire group was 22.6 months (mo), with a trend for shorter OS in the men with NEPC (20.7 mo) compared to CRPC (22.7 mo), p=0.11.

In the sample 47.6% of NEPC and 55% of CRPC had detectable CTC counts (p=0.58); 38.1% of NEPC and 40.0% of CRPC had greater than or equal to five CTCs (p=0.89).

CTC counts of 0 to 4 versus greater than or equal to five were prognostic for both groups: NEPC with 0 to 4 CTCs had median OS of 22.6 versus 6.6 mo for CTCs greater than or equal to 5 (p<0.001) and CRPC with 0 to 4 CTCs median OS not reached (mean 40.6 mo) versus 11.2 mo for those with greater than or equal to five CTCs (p<0.001). So, what does this mean? Men with NEPC have similar frequency of detectable and elevated CTC counts by the CellSearch methodology as compared to an overall CRPC population. The conclusion is that CTC counts are prognostic for both groups. Despite mounting data supporting the efficacy of CTC counts for prognostication it seems to remain a rarely used tool by most oncologists. Perhaps it is time that we prostate cancer survivors pus our doctors to consider using CTC counts, especially to measure the efficacy of our treatments. 2014 Genitourinary Cancers Symposium
Abstract No: 204

Citation:
J Clin Oncol 32, 2014 (suppl 4; abstr 204)
Author(s): Gurveen Kaur, Beerinder Singh, Himisha Beltran, Naveed Hassan Akhtar, David M. Nanus, Scott T. Tagawa; Weill Cornell Medical College, New York, NY; Department of Medicine, Institute for Precision Medicine, Weill Cornell Medical College and New York-Presbyterian Hospital, New York, NY

Joel T Nowak, M.A., M.S.W.