Prostate cancer is often a multifocal disease, meaning that several tumors can be present in different parts of gland at the same time. Not all of these tumors are equally problematic, however. And it’s increasingly thought that the tumor with the most aggressive features — called the index lesion — dictates how a man’s cancer is likely to behave overall. That concept has given rise to a new treatment option. Called partial gland ablation (PGA), and also focal therapy, it entails treating only the index lesion and its surrounding tissues, instead of removing the prostate surgically or treating the whole gland in other ways. Emerging evidence suggests that PGA controls prostate cancer effectively, but with fewer complications such as incontinence.

In February, researchers at Memorial Sloan Kettering Cancer Center (MSKCC) in New York published findings that could pave the way for focal therapy in men with reoccurring prostate cancer. They focused specifically on men whose cancer had returned three to four years on average after initial treatment with radiation.

Their findings, while preliminary, suggest that MRI and biopsy results can allow doctors to select which patients with reoccurring prostate cancer might be eligible for PGA. The research was headed by Dr. Gregory Chesnut, an MSKCC urologist.

During their study, Chesnut and his colleagues first identified 77 men who were treated for reoccurring prostate cancer at MSKCC between 2000 and 2014. All the men had initially been given radiation for their prostate cancer with an intent to cure the disease, but the cancer had returned. At that point they had their prostates surgically removed. Following that, sections of their tumors had been mounted on slides for a pathologist’s review, and then put into storage.

By looking at these slides with sophisticated instruments, Chesnut’s team was able to map out where the individual tumors in each of the men’s prostates were located. The team also had access to pre-operative information showing that 15 of the men were candidates for PGA according to current criteria. To be considered for PGA, men need to have a treatable index lesion and an absence of highly aggressive cancer cells outside that tumor’s immediate vicinity, according to biopsy and MRI findings.

What the results showed

What Chesnut and his colleagues wanted to know was if the men’s pre-operative findings were consistent with tumor details in their surgically removed prostates. And that turned out to be the case. The men truly did have treatable index lesions without other aggressive cancer, meaning that the biopsy and MRI results had accurately predicted PGA eligibility. Moreover, six additional men were found to be eligible for PGA based on tumor slide analysis, even though the pre-operative and MRI evidence had suggested otherwise.

Given that, the authors concluded that 21 of the initial 77 men, or 27% in all, had recurring prostate cancer that was amenable to PGA.

While the results are promising, the authors also cautioned that, given the small number of men evaluated and other study limitations, they are currently unable to recommend PGA as treatment for recurring prostate cancer outside of clinical trials.

“The authors have addressed a very important problem and one that has no easy answers, which is what to do about recurrent or persistent prostate cancer following radiation therapy,” says Dr. Marc Garnick, the Gorman Brothers Professor of Medicine at Harvard Medical School and Beth Israel Deaconess Medical Center, editor of the Harvard Health Publishing Annual Report on Prostate Diseases, 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. Alternatives that can help to eliminate persistent cancer in an irradiated gland, and thus lessen side effects, mark an important advance. These new findings should reassure men who undergo PGA that aggressive cancer in the prostate will not be left untreated. The findings are also important in that patients can be offered a second chance to remove residual or recurring cancer without having to undergo surgical removal of a prostate that’s already been treated with radiation. Further studies should explore these findings in larger numbers of patients.”