Genetic analysis of a prostate cancer can be misleading if it is based on only one biopsy, according to a study that found large differences in how aggressive different tumors can be in the same patient, or even within different parts of the same tumor.
The study, “Intratumoral and Intertumoral Genomic Heterogeneity of Multifocal Localized Prostate Cancer Impacts Molecular Classifications and Genomic Prognosticators,“ published in the journal European Urology, demonstrates that physicians should take care when basing treatment decisions on genetic analyses of prostate cancer.
Although most prostate cancers are relatively harmless, some are aggressive and need more potent treatment. Genetic analyses of tumor tissue, so-called genomic fingerprinting, is increasingly being used by physicians to help them choose an appropriate treatment.
To investigate if such an approach, based on only one biopsy, is feasible, a research team from the Cleveland Clinic analyzed tumors from four men who underwent radical prostatectomy, the removal of the entire prostate. Researchers took three biopsies from the main tumor (the tumor usually used for fingerprinting), and one each from smaller tumors within the prostate, and analyzed the tissue with various sequencing techniques.
The team found that genetic changes in the tumors differed not only between tumors in the same patient, but more importantly, within the same tumor as well. The results also differed depending on the sequencing method used. A look at public data from The Cancer Genome Atlas confirmed these findings.
“We examined the molecular composition of heterogeneous cancerous tumors in a patient’s prostate,” Hannelore Heemers, PhD, the study’s senior author, said in a news release. “We found a lot of genetic differences among these tumors, and concluded that information from a single cancer biopsy is not sufficient to guide treatment decisions.”
“Precise treatment is more complicated and the findings demonstrate a weakness in current genetic fingerprinting in prostate cancer,” she added.
James Mohler, MD, chair of the Department of Urology at Roswell Park Cancer Institute in Buffalo, New York, and a co-author of the study, also underscored the implications of the findings.
“Clinicians need to be careful about using the information from a gene-based test, because the analysis may not have been performed on the most aggressive portion of a man’s prostate cancer,” Mohler said.
An editorial by Alastair Lamb, PhD, a researcher at Cambridge University Hospitals in the U.K., applauded the study, but underscored that more research is needed to understand how prostate tumors might differ within individuals.
Heemers and her team fully concurred, also calling for more research into cancer differences and optimal methods to personalize treatments.