Widespread PSA screening has shifted prostate cancer diagnosis toward earlier-stage, lower-risk disease, creating a growing population of men with tumors that may never cause serious harm. Yet the two standard treatments -- radical prostatectomy (RP) and radiation therapy (RT) -- treat the entire prostate and carry significant risks of urinary incontinence, bowel problems, and erectile dysfunction. For many men with low-risk disease, these side effects may outweigh the benefit of treatment.
The alternative, active surveillance (AS), avoids treatment side effects but comes with its own limitations. Up to 33% of men on surveillance eventually need definitive treatment after 2-5 years, and 73% of those who undergo surgery turn out to have had significant cancer all along -- meaning their cancer was understaged at diagnosis. The psychological burden of living with untreated cancer also affects quality of life for many patients.
This clinical gap has motivated the development of focal therapy: the targeted destruction of cancer within the prostate while leaving healthy tissue and surrounding structures intact. Focal approaches are already standard in other solid tumors -- kidney, liver, breast, and brain -- where targeted ablation of localized disease has replaced whole-organ surgery in selected patients.
The biological rationale for focal prostate therapy rests on the observation that while prostate cancer is often multifocal -- present in multiple areas of the gland simultaneously -- virtually all lethal metastases originate from a single dominant clone called the index lesion. Histopathological features of this index lesion predict the clinical behavior of the entire gland in over 90% of patients, and the aggregate volume of secondary tumors is typically less than 0.5 mL. Treating only the index lesion may therefore provide meaningful cancer control without the morbidity of treating the whole organ.
Appropriate patient selection is critical to focal therapy's success, and criteria vary based on the intended goal. For curative intent, the ideal candidate has low-stage, low-risk, unifocal disease that can be completely eradicated from a clearly defined location. For disease control intent, focal therapy can treat the dominant lesion to slow progression and delay the need for radical treatment, extending the window of active surveillance for intermediate-risk patients.
Most published trials have enrolled low-risk patients -- defined by PSA, clinical stage, and Gleason score using the D'Amico classification -- because the risk of systemic relapse is low and local control is a meaningful endpoint. However, this means that the benefit of focal therapy over surveillance alone may be difficult to demonstrate in this group, since low-risk patients generally have favorable outcomes regardless of treatment.
The heterogeneity of Gleason 7 tumors creates important distinctions for selection. Gleason 3+4 tumors carry intermediate relapse risk and are reasonable focal therapy candidates. Gleason 4+3 tumors, however, have substantially higher risk of extraprostatic extension, metastasis, and upgrading on surgical pathology -- and have outcomes similar to Gleason 4+4 (Gleason 8). Patients with 4+3 disease therefore require more careful consideration before focal therapy is considered appropriate.
An important caveat in selection is the known risk of 30-40% upgrading of surgical pathology compared to biopsy pathology -- meaning a patient whose biopsy shows Gleason 6 may harbor Gleason 7 or higher disease in untested areas. This sampling limitation means that focal therapy selection decisions are only as reliable as the biopsy protocol used to stage the disease.
Standard transrectal ultrasound (TRUS) guided systematic biopsy using a 12-core pattern is the established diagnostic method, but it is poorly suited for focal therapy planning. Ultrasound cannot visualize most prostate tumors directly, so cores are sampled at predetermined locations rather than from suspicious tissue. If a 12-core biopsy shows cancer on one side only, there is still a 75% chance that cancer is also present on the other side -- making unilateral focal treatment decisions based on this data unreliable.
The three fundamental errors of random systematic sampling are: (1) underdetection -- missing a lethal cancer in an unsampled area; (2) overdetection -- identifying an insignificant cancer that would never progress; and (3) misclassification -- appearing to have low-risk disease when higher-grade cancer is present elsewhere. Even transperineal 3D mapping biopsy, which samples the entire gland every 5 mm using a grid template, found bilateral disease in over 61% of cases diagnosed as unilateral by TRUS biopsy and upgraded Gleason score in 27%.
Multiparametric MRI (mpMRI) addresses the visualization problem by combining T2-weighted imaging (anatomy), diffusion-weighted imaging (cell density), and dynamic contrast-enhanced sequences (vascularity) into a comprehensive 3D assessment. For clinically significant lesions -- those above the standard volume and grade thresholds -- mpMRI sensitivity and specificity reach up to 90%. In one series, sensitivity was 100% for peripheral zone cancer detection with a negative predictive value of 100%, meaning a negative mpMRI was highly reliable for ruling out significant disease.
MRI-ultrasound fusion biopsy overlays the pre-procedure MRI onto real-time ultrasound, allowing the urologist to biopsy the exact suspicious regions identified on imaging. Systems such as the Artemis device create a 3D template reconstruction of the prostate and track core positions. Fusion biopsy achieves a cancer detection rate of 55% versus 24-40% for standard 12-core biopsy, detects 16% more Gleason grade 4-5 cases, and upgrades Gleason score in up to 32% of cases compared to systematic sampling alone.
Focal cryotherapy uses extreme cold to destroy targeted cancer tissue. Probes inserted under ultrasound guidance deliver liquid argon or nitrogen, creating an expanding ice ball that kills cells through a combination of ice crystal formation, cell membrane rupture, and ischemia during thaw. The hemiablation approach -- treating one side of the gland while preserving the opposite side and neurovascular bundle -- is the most commonly used strategy, allowing potency preservation in men with unilateral disease.
Early clinical experience from Onik et al. in nine men with unilateral cancer showed all men with stable PSA and all six undergoing repeat biopsy were negative for cancer at 3-year follow-up, with seven of nine men potent. Larger follow-up series reported variable outcomes: biochemical recurrence rates range from 7% to 27% depending on definition criteria and follow-up duration, with most recurrences occurring in the untreated contralateral lobe -- suggesting initial staging failure rather than treatment failure.
The largest available dataset comes from the Cryo On-Line Data (COLD) registry. In 1,160 patients treated with focal cryoablation, the biochemical recurrence-free rate at 3 years was 75.7% using the ASTRO definition (three consecutive PSA rises). Among patients who underwent follow-up biopsy (14.1% of the total), 26.3% had positive results, representing only 3.7% of all treated patients. Urinary continence (zero pad use) was preserved in 98.4% of patients, and spontaneous erections were maintained in 58.1%.
One important limitation of interpreting cryotherapy outcomes is the lack of a standardized definition of PSA failure after focal ablation. Because only part of the gland is treated, PSA does not drop to near zero as it would after whole-gland treatment or prostatectomy. PSA typically decreases by 30-60% after focal therapy, and the residual PSA from untreated benign tissue makes biochemical recurrence definitions less reliable than in whole-gland treatments.
High-intensity focused ultrasound (HIFU) destroys tissue by focusing ultrasound energy to a precise point within the prostate, generating heat above 65 degrees Celsius and creating inertial cavitation -- microscopic bubbling that mechanically disrupts cells. The treatment is performed transrectally, guided by ultrasound imaging, without any skin incision. Most published data comes from whole-gland HIFU, which demonstrated biochemical disease-free rates of 45-84% at 5 years and 61% at 10 years in large series of up to 538 men.
Focal HIFU has been studied in smaller series. A comparison of 70 patients undergoing whole-gland HIFU versus 29 undergoing unilateral focal HIFU showed an 82% negative biopsy rate at 12 months with focal treatment, without compromising cancer control. In a 20-patient phase I/II trial of focal hemiablation, 95% of men reported erections sufficient for intercourse and 90% were pad-free at 12 months follow-up -- functional outcomes substantially better than radical treatment. A 12-patient 10-year follow-up study showed recurrence-free survival of 90% at 5 years, declining to 38% at 10 years.
Focal laser ablation (FLA) is a newer technique using laser energy delivered through a thin fiber inserted under MRI guidance. Its key advantage is real-time MRI monitoring during the procedure -- the treating physician can directly visualize the ablation zone forming in real time and confirm that it encompasses the entire tumor while avoiding the urethra, rectum, and neurovascular bundles. Phase I results showed 78% negative biopsies at the ablation site with no changes in erectile function or voiding symptoms.
Bipolar radiofrequency ablation (RFA) is another approach under investigation, using a specially designed probe that can be positioned to within 0.5 mm of a planned target using TRUS guidance. Though FDA-approved for prostate cancer treatment, no clinical outcomes trials had been published at the time of this review. These emerging techniques -- FLA and RFA -- represent a next generation of focal ablation tools that may offer more precise spatial control and real-time feedback than cryotherapy or HIFU.
Follow-up after focal therapy typically combines PSA measurement, mpMRI, and targeted rebiopsy. Each modality has limitations in this context. PSA is unreliable as the sole indicator because residual untreated benign tissue continues producing PSA, and the expected post-treatment decline is only 30-60%. No standardized PSA nadir or failure threshold has been validated specifically for focal therapy, complicating comparison across studies and institutions.
MRI is particularly useful for follow-up using the dynamic contrast-enhanced (DCE) sequence: treated tissue no longer enhances with contrast because its blood supply has been destroyed, creating a clear visible signal of the ablation zone. Immediate post-treatment imaging (within one week) demonstrates the extent of the ablation effect, while delayed imaging at 6 months can reveal residual enhancing cancer that was missed or undertreated.
Repeat targeted biopsy is the most definitive way to assess treatment success but carries the same sampling limitations as pre-treatment biopsy. The rigor of post-treatment biopsy should match that of the pre-treatment biopsy -- meaning MRI-targeted fusion cores of the treated area -- to accurately determine whether cancer has been eradicated. Use of the same systematic biopsy approach as standard of care would risk missing residual disease in non-sampled areas.
Focal therapy is at an early but promising stage of clinical development. It offers men with localized prostate cancer a middle path -- substantially less morbidity than radical treatment while providing more active cancer control than pure surveillance. Long-term randomized studies with consistent patient selection criteria, standardized treatment protocols, and well-defined follow-up end points are needed to establish focal therapy's role in routine clinical practice alongside surgery and radiation.