Prostate cancer is often a multifocal disease, which means that several tumors can be present in different parts of the gland at the same time. However, not all of these tumors are equally problematic. And it is increasingly believed that the tumor with the most aggressive characteristics – called the index lesion – dictates the overall behavior of cancer in humans. This concept gave rise to a new treatment option. Called partial gland removal (PGA), as well as focal therapy, it involves treating only the index lesion and its surrounding tissue, instead of surgically removing the prostate or treating the entire gland in some other way. New evidence suggests that PGA effectively controls prostate cancer, but with fewer complications such as incontinence.
In February, researchers at Memorial Sloan Kettering Cancer Center (MSKCC) in New York City published results which could pave the way for focal therapy in men with recurrent prostate cancer. They focused specifically on men whose cancer had come back on average three to four years after the initial radiation treatment.
Their results, although preliminary, suggest that MRI and biopsy results may allow doctors to screen for patients with recurrent prostate cancer who might be eligible for AGP. The research was led by Dr. Gregory Chesnut, an MSKCC urologist.
During their study, Chesnut and colleagues first identified 77 men who were treated for recurrent prostate cancer at MSKCC between 2000 and 2014. All of the men had initially received radiation therapy for their prostate cancer in the goal of curing the disease, but the cancer had returned. At that time, they had their prostate surgically removed. Subsequently, sections of their tumors were mounted on slides for examination by a pathologist and then stored.
By viewing these slides with sophisticated instruments, Chesnut’s team were able to determine where the individual tumors were in each of the men’s prostates. The team also had access to preoperative information showing that 15 of the men were candidates for PGA under current criteria. To be considered for PGA, men must have a treatable index lesion and an absence of very aggressive cancer cells outside of the immediate vicinity of that tumor, according to the results of the biopsy and MRI.
What the results showed
What Chesnut and his colleagues wanted to know was whether the men’s preoperative results were consistent with the details of the tumor in their surgically removed prostates. And it turned out to be the case. The men did have index lesions that were treatable without further aggressive cancer, meaning the biopsy and MRI results accurately predicted eligibility for PGA. Additionally, six additional men were found to be eligible for PGA based on tumor slide analysis, even though preoperative and MRI evidence suggested otherwise.
Taking this into account, the authors concluded that 21 of the initial 77 men, or 27% in total, had recurrent prostate cancer that was susceptible to PGA.
While the results are promising, the authors also cautioned that, given the small number of men assessed and other limitations of the study, they are currently unable to recommend PGA as a treatment for cancer of the recurrent prostate outside of clinical trials.
“The authors touched on a very important problem to which there are no easy answers, namely what to do with recurrent or persistent prostate cancer after radiation therapy,” says Dr. Marc Garnick, professor. of Gorman Brothers Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, Editor-in-Chief of Harvard Health Publishing Annual report on prostate disease, and editor-in-chief of HarvardProstateKnowledge.org.
“Performing a radical prostatectomy to remove the prostate after radiation therapy is a complicated procedure, associated with potentially significant urinary side effects. The alternatives that can help eliminate persistent cancer in an irradiated gland, and thereby alleviate side effects, are an important step forward. These new findings should reassure men who undergo PGA that aggressive prostate cancer will not be left untreated. The results are also important as patients can be offered a second chance to rule out residual or recurring cancer without having to undergo surgical removal of a prostate already treated with radiation therapy. Further studies should explore these results in a larger number of patients. “