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Researchers have found an association between baseline circulating tumor cell count and survival in metastatic hormone-sensitive prostate cancer.
Among patients with hormone-sensitive prostate cancer, circulating tumor cell (CTC) count at the start of treatment may be able to indicate which patients are likely to live longer after treatment, as well as those who may be good candidates for novel therapies and clinical trial enrollment, researchers have found.
Researchers from a study published in JAMA Network Open studied 1,313 men starting systemic hormone therapy for metastatic hormone-sensitive prostate cancer (mHSPC) in the phase 3 S1216 clinical trial. They found that among evaluable samples from 503 patients collected at baseline and 93 samples collected at progression, elevated CTC count at baseline was associated with statistically significantly worse overall survival (OS), progression-free survival (PFS) and treatment response, according to the study findings.
“Patients have tumors that actually, we now know, can shed material into the bloodstream. There are cancer cells that are shed from the tumor into the blood circulation, and we refer to those as circulating tumor cells,” explained study co-author Dr. Amir Goldkorn in an interview with CURE®.
Goldkorn is the Division of Medical Oncology, Department of Medicine, Keck School of Medicine of USC, Los Angeles.
Hormone-sensitive prostate cancer: cancer that needs male hormones to grow.
Overall survival (OS): the time a patient lives, regardless of disease status.
Progression-free survival (PFS): the time a patient lives without their disease spreading or worsening.
Prostate-specific antigen: a protein associated with the presence of prostate cancer in the body.
Circulating tumor cell count can be measured via a simple blood draw, known as a liquid biopsy. Researchers found five or more CTCs per 7.5 milliliters (mL) of blood drawn in 60 samples (11.9%), one to four CTCs per 7.5 mL in 107 samples (21.3%) and no CTCs per 7.5 mL in 336 samples (66.8%).
The median OS for men with five or more CTCs per sample was 27.9 months versus 56.2 months for men with one to four CTCs per sample and not reached at 78 months follow-up for men with no CTCs per 7.5 mL, meaning more than half of those patients were still alive.
“One baseline test right at the start of when they began hormonal therapies and everything else was able to predict how well patients were going to respond to the treatment, how long they would be responding to the treatment, and how long overall they would be living with various treatments for prostate cancer,” Goldkorn said. “This is despite the fact that all these men went on to have hormonal therapies, and then they maybe progressed and went on to other treatments and chemo and this and that, you go on multiple lines of therapy for years. And yet, regardless of all that downstream stuff, that first baseline test was able to tell us, ultimately, who was going to have a shorter expected life on with their cancer, and who was going to survive much longer.”
Researchers further reported that after adjusting for baseline clinical covariates, patients with five or more CTCs per sample had significantly higher hazards of death and disease progression and a lower likelihood of prostate-specific antigen complete response versus men with no CTCs in their sample.
“The results of this prognostic study show that baseline elevated CTC count was associated with poor response, rapid progression and poor survival, reflecting innate aggressive phenotypes that remain consistent throughout the disease course and after subsequent lines of therapy,” researchers concluded in the study. “Given these characteristics, baseline CTC count may be used to facilitate clinical development of new, more effective treatments. Specifically, in men with newly diagnosed mHSPC, of whom two-thirds generally have good performance status and years of life expectancy, baseline CTC count may identify the one-third of men with more aggressive disease who are likely to experience worse outcomes. In this new generation of trials, elevated CTC count may serve as a valuable baseline biomarker to enrich the study cohorts for men most likely to benefit from these more aggressive therapeutic strategies.”
“Prostate cancer is really the most common cancer in U.S. men, metastatic prostate cancer is the second most lethal cancer for U.S. men, so we see lots and lots of men in our practice who come in with metastatic disease, which currently is not curable,” Goldkorn said. “And we're developing a variety of new treatments that do extend life, obviously, [but] treatments also have side effects, and so we urgently need biomarkers or tests or assays that could tell us who which men coming in with metastatic prostate cancer are going to do very well with given treatments, which men are going to have much more aggressive disease and perhaps have shorter survival. And so, this study was an attempt to identify one such biomarker that could help us understand who's going to live longer, who's going to live shorter with their metastatic disease and help us perhaps make some decisions accordingly about their care.”
Patients with high CTCs at baseline may be good candidates for clinical trial participation and treatment with novel therapies, as researchers noted and Goldkorn explained.
“High CTCs mean you're not going to do well what we have, you're not going to have as long a lifespan,” Goldkorn said. “Maybe those men should be offered the novel therapies that they could do better with, right? So it's a very it's a very important distinction. We're not saying, ‘Oh, now CTCs can help us know which drug to [use], we have 10 drugs now we know which one to give you based on your CTC account.’ No, we just know that you're not going to do very well overall with these treatments that we now have. If newer things come along, maybe those are the patients that we should offer preferentially, those new, more aggressive therapies.”
Reference
“Circulating Tumor Cell Count and Overall Survival in Patients With Metastatic Hormone-Sensitive Prostate Cancer” by Dr. Amir Goldkorn et al., JAMA Network Open.
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