Patients with newly diagnosed, unfavorable, intermediate-risk prostate cancer often represent a grey zone of clinical decision making. Two patients could share the same characteristics — for instance, their tumors have a Gleason score of 4+3 with otherwise favorable features — but these individuals could have very different disease courses even if they receive the same treatment. Some clinicians see a need for tools that can better stratify this patient population to identify those who might benefit from aggressive therapy.
A study in Urology suggested that the Oncotype DX Genomic Prostate Score® (GPS) assay — which is currently indicated for guiding treatment decisions in low-risk and favorable intermediate-risk disease at the time of diagnosis — could also help predict long-term clinical outcomes in men with unfavorable intermediate-risk disease.1 Along with a patient’s prostate-specific antigen (PSA) level at diagnosis, as well as the grade and stage of the cancer, the authors suggested the assay could help inform clinicians and patients’ treatment planning.
“If you were below [a GPS score of] 40, your cancer was going to behave more like lower-risk disease, whereas if you had a score above 40, it was going to behave more like high-risk disease, where it’s clear that we need to treat more aggressively,” said Jennifer Cullen, PhD, MPH, associate professor and associate director of cancer population sciences at the Case Comprehensive Cancer Center in Cleveland, Ohio, and lead author of the study.
The GPS assay ascertains the expression levels of 17 genes — 12 are cancer-related, and 5 are controls — in mRNA extracted from tumor biopsies, and produces a score from 0 to 100 to indicate the aggressiveness of the tumor. According to current National Comprehensive Cancer Network (NCCN) and American Society for Clinical Oncology (ASCO) guidelines, the test may be offered to patients who have been newly diagnosed with low-risk or favorable intermediate-risk disease, and could help a physician determine if active surveillance or a more aggressive therapy would be the best clinical course for a patient.2,3
The new research aimed to understand whether the GPS assay could also be useful in men diagnosed with unfavorable intermediate-risk disease. In these patients, the decision whether more aggressive treatment is warranted is a more complicated one.
Dr Cullen and colleagues undertook a statistical analysis of GPS data collected from 2 previously studied cohorts of men with intermediate-risk disease who had been treated with radical prostatectomy.4,5 One cohort included patients treated at 2 US military medical centers. This was more diverse than the second cohort, which comprised a number of patients treated within the Kaiser Permanente Northern California system. Otherwise, the 2 cohorts were similar save for small differences, Dr Cullen explained. Taken together, there were 175 individuals with unfavorable, intermediate-risk disease.
The authors found that when GPS scores were assessed as dichotomous values (either above or below 40), they could be used as predictors of the time to biochemical recurrence of disease (BCR), development of distant metastases (DM), and prostate-specific death (PCD) after surgery.
For instance, men with GPS scores lower than 40 had BCR rates similar to patients with favorable, intermediate-risk disease, and their 10-year risk of BCR was around 12%. However, patients with GPS scores higher than 40 had BCR rates similar to those with high-risk prostate cancer, with most projected to experience BCR within 10 years.