Prostate Health Index May Provide New Tool to Identify Patients Assigned to Watchful Waiting Who Require Immediate Treatment
A simple tool called “phi” appears to be able to identify which patients assigned to active surveillance for prostate cancer are more likely to require treatment. Phi, or the prostate health index, is calculated from three serum measurements: PSA, free/total PSA, and a new measurement, [-2]proPSA, using the Beckman Coulter assay kit. In the study, phi gave a more accurate estimate of patients’ course of illness than either PSA alone or free/total PSA. The findings were presented at the 2014 Genitourinary Cancers Symposium in San Francisco (Abstract 81).
“This is exciting. It is a new way to work out which patients assigned to watchful waiting will need treatment. There are many patients who don’t need treatment even 10 years after diagnosis,” said lead author Andrew Eichholz, MD, of The Institute of Cancer Research, The Royal Marsden NHS Foundation Trust, Sutton, United Kingdom.
Dr. Eichholz explained that phi is starting to be used in the prebiopsy setting in the United States. Although he is quite enthusiastic about the applicability of the new tool, he said, “It is not ready for prime time. The phi index needs to be validated. We are the first group to study it, and another group is also studying it. If it is validated, it could massively change the way we manage these patients.
Study Details
The study was a retrospective analysis of patients’ frozen blood samples collected at diagnosis a median of 11.4 years ago. The investigators sought to determine the predictive value of phi. The study included 370 patients with prostate cancer with T1/T2 tumors, Gleason scores of ≤ 3+4, and PSA < 15 ng/mL.
Ten years later, 37% of patients still did not require treatment, while about 20% needed treatment within 2 years of diagnosis.
Patients were grouped into quartiles according to phi. The investigators determined that the cutoff point for phi was ≤ 31.4 for the lowest-risk quartile, and > 58.5 for the highest-risk quartile. Among lowest-risk patients, 95% would not need therapy within 5 years from diagnosis, while among highest risk, 54% would require treatment within 5 years.
“If validated, phi will be useful for advising patients. It will be an extra tool for our discussions,” Dr. Eichholz stated.
The study was funded by Beckman Coulter. For full disclosures of the study authors, view the study abstract at www.gucasym.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
