At the 2013 European Cancer Congress in Amsterdam Dr. Howard Scher from Sloan Kettering Hospital reported that a panel of biomarkers could identify men with metastatic, castration-resistant prostate cancer (mCRPC) who were responding well or less well to treatment with Zytiga + prednisone (abiraterone + prednisone).

Dr. Scher provided data in his presentation to support the two following concepts:

!- At 12 weeks after initiation of Zytiga therapy the number of circulating tumor cells (CTCs) in combination with serum levels of lactate dehydrogenase (LDH) can predict how well the Zytiga has worked.

2- If the combination of abiraterone acetate + prednisone has not provided a substantial clinical benefit at 12 weeks, no further improvement in patient outcome can reasonably be expected.

The data presented by Dr. Scher was based on a risk assessment of 711 men with chemotherapy-naive mCRPC who participated in the second major randomized Phase III clinical trial of abiraterone acetate + prednisone vs. a placebo + prednisone (the COU-AA-30 trial).

Dr. Scher is was quoted, “The probability of being alive at 2 years was 46 percent for patients in a good risk category, while if patients were in a high-risk category at the same time point, the probability of being alive was 2 percent.

As part of the clinical trial protocol 711 men had a number of different markers measured on a regular basis. These markers included their circulating tumor cells (CTC), LDH levels as well as their PSA level (after 12 weeks). The men were then divided into three different risk groups:

“High-risk” if their CTC count was >=5 and their LDH level was >250 IU/l

“Intermediate-risk” if their CTC count was >=5 but their LDH level was <=250 IU/l“Low-risk if their CTC count was >4 and their LDH level was within the normal range.

They also found that at 12 weeks after initiation of treatment with abiraterone acetate:

1- 46 percent of men with low-risk disease according to the above criteria were still alive after 2 years on treatment.

2- Only 2 percent of men with high-risk disease were still alive after 2 years on treatment.

According to Dr. Scher these data appear to provide us with a way to determine which men should be maintained on Zytiga for a period longer than 12 weeks and which men should be advised to consider an alternative management strategy after such a time period.

Dr. Scher said, “…it is a huge difference, and it’s telling us that the 12-week post-treatment measurement of this biomarker gives you a pretty good estimate of a patient’s prognosis. We would argue that if patients are still in a high-risk category at the 12-week point, physicians should consider doing something else”.

Scher HI, Heller G, Molina A, et al. Evaluation of a composite biomarker panel including circulating tumor cell enumeration as a surrogate for survival in metastatic castration-resistant prostate cancer. Presented at: European Cancer Congress 2013; September 27-October 1, 2013; Amsterdam, The Netherlands. Abstract 2851. – See more at: http://www.onclive.com/conference-coverage/ecco-esmo-2013/Biomarkers-Predict-Prognosis-for-Patients-With-mCRPC#sthash.eg6wyFAM.dpuf

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