Trial Marks Success of Precision Medicine in the Treatment of Prostate Cancer
Consider these facts on prostate cancer. More than 200,000 men will develop prostate cancer this year, making it the #1 cancer in men after skin cancer. Almost 30,000 men will die of prostate cancer, second only to lung cancer.
Precision medicine has transformed the approach to treating cancer. In contrast to conventional chemotherapy which involves toxic drugs which kill both cancerous and normal cells, causing many side effects, precision medicine selectively targets a patient’s unique tumor characteristics. Recently, an exciting study was published that is the first demonstrating the efficacy of precision medicine in prostate cancer.
Researchers studied 49 men with metastatic hormone-resistant prostate cancer who had previously been treated with standard therapy. Patients were given the PARP inhibitor, olaparib. Those whose tumors harbored a DNA repair mechanism defect demonstrated a high response rate, defined as a reduction in PSA, tumor burden, radiologic response or a decrease in circulating tumor cells.
PARP is a DNA repair mechanism that works to repair DNA strand breaks, thus promoting cell survival. With PARP inhibition, cells will die. This pathway is exploited in tumors in which there exists a mutation in DNA repair genes. By preventing repair of tumor DNA, the cell will die.
The study also demonstrated the feasibility of profiling tumor DNA by next generation sequencing to identify patients with such mutations. This highlights the important role pathologist’s play in precision medicine.
Pathologists are involved in each step of the process. First, a tumor may be biopsied in either the operating room or radiology under CAT scan guidance. Pathologists are called upon to assess the sample, ensuring it is adequate for both diagnosis and testing for precision medicine targets (“actionable mutations”).
In the lab, pathologists examine tissues under the microscope using various stains to make a diagnosis. When appropriate, a tumor is tested for the presence of “actionable mutations”. If discovered, the patient may be eligible for targeted therapy. The success of precision medicine depends on pathologists.
There promises to be many more such successes with precision medicine as our understanding of cancer expands.