[Circulating prostate cells and bone marrow micrometastasis are determinant in risk and time to biochemical...

Minimal residual disease (MRD) is that which remains after curative therapy for prostate cancer. It has the potential for growth and later cause metastasis. After radical prostatectomy, the detection of circulating prostate cells (CPCs) and bone marrow micro-metastasis could represent different types of MRD. We proposed to determine the biochemical failure free survival rates, the time to biochemical failure after 10 years of follow-up and the presence of CPCs and micro-metastasis in patients treated with RP for pathologically organ confined prostate cancer.

One month after RP monotherapy for prostate cancer, blood and bone marrow samples were taken to detect CPCs and micro-metastasis. Men were classified as: group A (CPC negative and micro-metastasis negative), group B (CPC negative and micro-metastasis positive), group C (CPC positive and micro-metastasis negative), and group D (CPC positive and micro-metastasis positive). All subjects were followed with serial total PSA levels, recording the time at which failure occurred defined as a serum PSA > 0.2ng/ ml on two separate occasions. After ten years of follow- up for each group Kaplan-Meier survival curves were determined and using an adjusted flexible parametric model (FP), the Restricted Mean Survival Times for groups A, B, C and D were calculated. RESULTS: 191 men participated, 10-year biochemical failure survival rates were; group A (N=114) with a Kaplan-Meier of 98.7%; group B (N=39) 65.1%; group C (N=12) 10.4% and in group D (N=28) 12.8%. The Restricted Mean Survival Times (years) were group A: 9.95; group B: 9.45, group C: 5.11 and group D: 6.18 (p-value <0.001 between groups: A versus C, Aversus D, B versus C and B versus D). Frequency and time to failure was dependent on the type of MRD, those men CPC positive had a significantly higher failure rate and early failure. Those men only micro-metastasis positive had lower failure rate and late failure when compared with men negative for MRD.

CPC positive men have a more aggressive disease with increased early failure; those men who are only positive for micro-metastasis are at risk for late or delayed failure. These two forms of measuring MRD represent different stages in the disease progression and may be used to guide clinical treatment decisions before increases in PSA levels.