Focal Therapy for Low-Risk Prostate Cancer
Transverse ultrasound image showing ice ball encompassing most of the prostate.
Although the traditional approach to prostate cancer has been to target the entire gland, Cleveland Clinic has offered focal cryotherapy on a very limited basis since 2005 for men with low-risk disease who understand the implications of all treatment options.
Long-term data are limited for focal cryotherapy, but an abstract presented at the 2008 American Urological Association annual meeting reported outcomes in 341 men treated with focal therapy whose data are recorded and tracked in the industry-sponsored Cryoablation-On-Line Dabatase (COLD) Registry. Biochemical disease-free survival, according to the American Society for Therapeutic Radiology and Oncology criteria, was 83% at 18 months; 74% of men were potent 36 months after treatment.
Reluctance to utilize focal therapy is largely based on the knowledge that most index prostate tumors are accompanied by smaller “satellite” lesions and approximately 80% of men with prostate cancer have bilateral disease.
However, research showed that 80% of secondary tumors are less than 0.5 cc, the lower threshold for detection using current MRI technology, which is a common criterion for depiction of clinical insignificance. Most cancers now are detected sooner than in the past and are, therefore, markedly smaller and earlier in their course.
Even in the setting of multifocal disease, the index tumor was found to predict accurately clinical behavior in more than 90% of patients. Thus, small synchronous tumors may truly be “clinically insignificant,” and limiting treatment to the area of tumors large enough to identify using MRI and emerging technologies becomes appealing.There is no consensus on what “focal” means. Some advocates attempt to treat only areas of known cancer. Others administer hemispheric treatment of the involved side, while some centers treat the entire gland with the exception of the area of the contralateral neurovascular bundle. The most common approach at Cleveland Clinic is the last, which we have found preserves potency in most men and is associated with low risk of side effects compared with whole-gland therapy using cryotherapy or radiation therapy options.
Patients undergoing focal therapy at Cleveland Clinic comprise a highly selected group of men with small, unilateral primary tumors. All men undergo a repeat 20-core saturation biopsy in the office under periprostatic block to confirm that they truly have limited disease, and those found to have contralateral atypia or prostatic intraepithelial neoplasia are excluded.
Candidates for focal therapy are informed of all other management options. We have found that most men who choose focal therapy are those who would be excellent candidates for active surveillance with delayed curative intent but are hesitant to leave their cancers untreated. Focal cryotherapy offers these patients an acceptable intervention with limited morbidity even if potency is not a priority. Another group that finds focal therapy appealing is composed of men who prioritize potency above cure.
Finally, men with persistent cancer confined to one lobe following radiation therapy are sometimes considered for focal therapy based on higher risks in the salvage setting compared with primary treatment. All patients are informed that the gold standard for treatment is whole-gland therapy and that normal preoperative potency is maintained in approximately 80% of men. We recommend a saturation biopsy be performed several months after focal therapy to assess for complete response.Persistence of significant disease identified on subsequent biopsy is typically re-treated with focal or whole-gland cryotherapy, radiation therapy, or radical prostatectomy.