Prostate cancer is the most diagnosed cancer in men. It is estimated that about one in seven men will develop it during a lifetime. When diagnosed early, this cancer is very treatable. The survival rate of men with localized and early detected prostate cancer is almost 100%. However, sometimes the disease is diagnosed too late when cancer has spread to the bones. In this case, it becomes severe and incurable. The five-year survival rate is only 29% for men who already have metastases to the bones. However, further research may help control better this disease.
Today, lytic metastases, which destroy bone tissue, and blastic metastases, which build new bone tissue from cancer cells, are treated in the same way as primary tumors of the prostate from which they come. However, according to a study published in the Journal for Immunotherapy of Cancer, this approach is wrong. According to researchers at the University of Colorado Cancer Center, targeted therapies and immunotherapy against cancer, which are ineffective against primary prostate cancer, may work against bone metastases depending on their nature. Specific therapies are a relatively new type of treatment, specifically targeting cancer cells, with fewer disturbances to normal cells. Additionally immunotherapy could stimulate the patient’s immune system to strengthen its defenses against cancerous cells.
“We have studied a collection of samples of human bone tissue, containing prostate cancer with characteristics of lytic and blastic disease”, explained the researchers. During their work, they noticed that the genetic and cellular landscapes of these two types of metastases were different.
Direct measurement of immunotherapy in bone metastases
“I was very shocked by the increase in pSTAT3 (genetic sign pathway) in patients with blastic tumors. I expected these bony (blastic) lesions to have few or no specific targets. I am happy to be wrong because these are the most common lesions in patients with prostate cancer,” says Claire Ihle a Ph.D. student in the lab of Colorado University Cancer Center.
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And while primary prostate cancers tend not to cause an immune response, they found that blastic and lytic metastases have high levels of the PD-L1 protein. This may mean that they are more likely to respond to the class of cancer immunotherapy called immune checkpoint inhibitors.
“The other interesting point of our study is that we developed a test that can directly measure immunotherapy and pathway targets in bone metastases,” says Philip Owens, the first author of the article. “This is significant because we could potentially use this as a test to determine which of the many immunotherapies could be best for an individual patient, one at a time, and truly provide personalized therapy.
New therapies and drug combinations
Researchers are now working to develop therapies with models of lytic and blastic bone metastases in mice. If all goes well in the long run, it could pave the way for new therapies that can treat these metastases that make prostate cancer a potentially fatal disease.
Currently, hormone therapy is the main treatment for metastatic prostate cancer. It can be administered along with radiotherapy or chemotherapy.
In May, a study published in the Journal of Clinical Precision Oncology had already shown that 57% of the 3,500 cancer samples from men with advanced prostate cancer had genomic characteristics indicating that the disease could be treated with targeted therapy. “More than half of the cancers in patients in this study have characteristics for which pharmacological targets are available. These results provide essential information on how we can design new clinical studies or drugs that will better treat men with advanced prostate cancer,” the researchers noted.