A common treatment for men with moderate risk of prostate cancer is to combine radiation with drugs that block testosterone – a hormone that makes tumors grow faster. (This type of treatment is also known as androgen deprivation therapy, or ADT).
New research suggests that the order of these treatments could be critical.
Dr. Dan Spratt, professor of radiation oncology at the University of Michigan, led the research. He and his colleagues have pooled data from two previously published clinical studies (here and here). In total, just over 1,000 men took part in the studies and were randomly assigned to one of two groups:
- Pre-radiation hormone therapy (followed by both treatments in all cases) or
- Hormone therapy that either started at the same time as the radiation and was continued after the radiation was finished, or started after the radiation was finished.
As such, the individual studies showed no significant difference in the results after an average follow-up period of almost 15 years. By combining the data, the Spratt team created a data set with sufficient statistical power to show that men had also started hormone therapy during or after The radiation was significantly better in every way: compared to the men who were treated with hormone therapy first, they were less likely to experience increases in prostate-specific antigen levels (suggesting the cancer may return). they lived longer without their disease getting worse; and cancer was less likely to spread to other parts of the body. The results also suggest that they had a lower risk of actually dying from prostate cancer, although that particular finding was not statistically significant.
Researchers have already paid a lot of attention to how long the hormone therapy should last with radiation. This is the first study to show that the order is also important.
Why should that be so? Possible explanations relate to testosterone’s ability to repair genetic damage in irradiated cancer cells. How sequencing affects this repair mechanism is unknown, but according to Dr. Spratt, the new results indicate ways for further investigation.
Importantly, the results apply specifically to men with unfavorable, intermediate-risk prostate cancer who typically receive hormone therapy for four to six months. According to Spratt, sequencing may not be as relevant for men with high-risk tumors who can be treated with hormones for several years.
Dr. Marc Garnick, Professor of Medicine at Gorman Brothers at Harvard Medical School and Beth Israel Deaconess Medical Center, Editor of Harvard Health Publishing Annual report on prostate diseasesAccording to the editor-in-chief of HarvardProstateKnowledge.org, there are circumstances in which some men may need hormone therapy prior to radiation. Describing the new results as compelling, he adds, “Efforts to prospectively (i.e., forward in time) sequencing should become an important part of future research.”