Researchers have created a test that they say can predict whether a man is at high risk of prostate cancer recurrence.
The research team, led by Prof. Robert Bristow of the Princess Margaret Cancer Centre and the University of Toronto, both in Canada, presented their findings at the 33rd conference of the European Society for Radiotherapy and Oncology (ESTRO33) in Vienna, Italy.
For men with cancer confined to the prostate, surgery and precision radiotherapy are the primary treatments. However, Prof. Bristow explains that during initial treatment, whether the cancer has spread outside the prostate often goes undetected. This means the cancer will return in 30-50% of patients.
"Men who fail treatment within 2 years may be at the highest risk of dying from their prostate cancer," he explains. "Existing methods for identifying high risk patients are imperfect, so new tests are required that are better at predicting which patients will have their cancer recur."
Therefore, the researchers set out to create such a test.
For their study, they analyzed the prostate cancer tissue of 126 men who had undergone image-guided radiotherapy (IGRT) - treatment that focuses solely on the tumor in the prostate area. All men were predicted to have an intermediate risk of their cancer returning and were followed for an average of 7.8 years.
To investigate DNA in the men's tissue samples, the researchers used array comparative genomic hybridization (aCGH). This is a process that assesses a patient's whole genome and spots regions where there are sections of missing, additional or abnormal DNA.
Through information gained using this technique, the researchers created a genetic "signature" that was able to accurately identify men who were at high or low risk of prostate cancer recurrence.
Genetic signature and tumor oxygen levels boost test accuracy
The researchers then tested this genetic signature on another group of 150 men who had their prostate cancer tumors removed via radical prostatectomy. These patients were also deemed as being at intermediate risk of cancer recurrence.
Fast facts about prostate cancer
- Prostate cancer is the most common form of cancer in American men.
- Approximately 233,000 new cases of prostate cancer will be diagnosed in the US this year.
- Around 6 in 10 diagnoses are among men aged 65 and older.
The researchers found that using the genetic signature, they were able to accurately predict which men were at high or low risk of their prostate cancer returning, just as they were in the first group.
In a subsequent experiment, the team tested the oxygen content of tumors from men who had undergone IGRT. They found that the oxygen content of tumors alone was also able to predict the risk of patients' cancer recurrence.
However, the researchers combined the genetic signature with information about the tumor's oxygen content to develop a test that can predict a man's risk of prostate cancer with close to 80% accuracy.
Overall, the researchers found that men with low levels of genetic changes and low oxygen content in their tumors were less to likely to experience recurrence of prostate cancer, with 93% surviving for 5 years without it returning.
Men who had high levels of genetic changes and high hypoxia (oxygen deprivation) were at higher risk of recurrence, with only 49% surviving for 5 years without prostate cancer returning.
Prof. Bristow says the team needs to validate the test over the next 2-3 years. But if all goes to plan, he says their findings could lead to a new test for cancer patients that will enable doctors to determine which patients require treatment that is not confined to the prostate region.
"These men can then be offered additional treatments, such as chemotherapy and hormone therapy, that will combat the prostate cancer throughout their entire body, rather than therapies solely focused on the prostate, in order to improve their chances of survival," he adds.
"These results will enable us to develop a new way of personalizing medicine, so that we can improve cure rates and reduce the chances of the cancer spreading to other parts of the body."