When you study about prostate cancer treatment you read an awful lotabout androgen deprivation therapy, radiation therapy and chemotherapy – because they work. You hear less about immunotherapy for prostate cancer because, despite its effectiveness against many cancers and other diseases, prostate cancer has been notoriously resistant to it.
...which is a shame, because immunotherapy is such a favored approach to disease-killing. The procedure is all about using – often times “tricking” – your own body's defense mechanisms against the sickness. This can take the form of man-made antibodies, immune checkpoint inhibitors that take the brakes off your immune system, and even “cancer vaccines.”
But scientists at the University of Texas' MD Anderson Cancer Center dug a little more deeply into our body's immune response to prostate cancer and discovered that if they approached it from two directions at once they could finally penetrate the tumor and make it “stick.”.
“We’ve known that prostate cancer is immunologically cold, or quiet, with very little penetration of the tumors or their surrounding microenvironment by immune cells,” said study leader Padmanee Sharma, MD, PhD.
“Our study explored whether we could increase immune cell infiltration by combining the anti-hormonal drug Lupron with two rounds of the checkpoint inhibitor ipilimumab before surgery in patients with locally advanced prostate cancer,” Sharma said.
The researchers learned that, in a conventional immunotherapy procedure, the white blood cells that are your immune system's weapon of choice would penetrate the prostate tumor, but other compounds within the tumor would then be activated which negated the overall immune response. So they plotted a two-pronged attack, following the first penetration up with drugs normally prescribed for Hodgkin lymphoma, lung, kidney, bladder and head and neck cancers to suppress the suppressors.
The study “...highlights the importance of studying immune response longitudinally,” Sharma said. “Observing immune response at one point in time doesn’t reflect what’s going on because the immune system is so dynamic. So baseline sampling in prostate tumors shows minimal immune infiltrate... Understanding these changes using post-treatment or on-treatment biopsies is important to develop rational combination strategies for these immune-modulating drugs.”
In the pre-surgical clinical trials, 17 patients participated. Sixteen completed treatment and surgery and one died of a cardiac complication before surgery. Six patients had their cancer progress and 10 were without evidence of progression for at least 3 and a half years.
The study was published in Nature Medicine.