Targeting the Highest Risk Tumor in Prostate Cancer

Targeting the Highest Risk Tumor in Prostate Cancer

(By Jeni Crockett-Holme)

Keywords: Prostate cancer, Minimally invasive, Focal therapy, Outcomes, Side effects

Like removing the leader of a pack, it might be possible to control prostate cancer and reduce treatment side effects by removing only the largest, most aggressive tumor [1]. A minimally invasive approach called focal therapy makes it possible to target this tumor, called the “index lesion,” and limit damage to surrounding tissue [2]. Focal therapy has been used successfully to remove all tumors in a prostate and to reduce side effects. Could comparable success be achieved by treating only the highest risk tumor?

The study
Prostate cancer often involves more than one tumor [1]. The largest tends to be the most aggressive, accompanied by two or three smaller, lower grade tumors. Removal of the prostate has typically been used to remove all of the cancer but at substantial risk to patients’ quality of life [1,3]. Many patients experience erectile dysfunction, incontinence, and other complications following prostate removal.

A small study of 56 patients with more than one prostate tumor looked at the occurrence of side effects after removal of the highest risk tumor. Other outcomes included absence of cancer that required treatment (clinically significant) at 1 year. Therapy involved locating the tumor with an MRI scan and a prostate biopsy and destroying it with high-intensity focused ultrasound (HIFU). Low-risk tumors were left untreated.

Results
The results showed that side effects were low and control of cancer was acceptable. Rates of functional preservation were not as high as those reported in some studies of focal therapy to all tumors; however, at 1 year after treatment, the majority of patients were continent and had erectile function sufficient for intercourse, and 86% were free of clinically significant cancer. At follow-up, two patients had cancer in untreated areas that required treatment. It was unclear whether these tumors were initially overlooked or were lower risk tumors that progressed after treatment.

Practical implications
This study was unique in leaving low-risk tumors untreated. The approach is based on data showing that low-risk tumors are unlikely to develop or spread (metastasize). If targeting of the highest risk tumor is successful, focal therapy might be an option for most men newly diagnosed with prostate cancer.

Targeting focal therapy to the largest, most aggressive prostate tumor was shown to be a feasible, safe, and well-tolerated treatment in the short term. Studies are needed to compare its effectiveness for cancer control with that of whole-gland therapy.

[1] Ahmed HU, Dickinson L, Charman S, et al. Focal ablation targeted to the index lesion in multifocal localised prostate cancer: a prospective development study. Eur Urol 2015;68:927–36.

[2] EAU patient information: glossary of terms prostate cancer. http://patients.uroweb.org/fileadmin/files/english/PCa/Glossary_of_terms_prostate_cancer.pdf. Accessed November 8, 2015.

[3] EAU patient information: localized prostate cancer. http://patients.uroweb.org/fileadmin/files/english/PCa/03_Localized_prostate_cancer.pdf. Accessed November 8, 2015.