Focal Cryotherapy in the Treatment of Localized Prostate Cancer

Huy D. Nguyen, BS; Bryan J. Allen, MD; Julio M. Pow-Sang, MD

Disclosures

Cancer Control. 2013;20(3):177-180. 

In This Article

Evaluation of Patients for Focal Therapy

Prostate cancer presents more often as multifocal disease. However, most of the areas are considered to harbor insignificant tumors. It is hypothesized that the index lesion (largest tumor volume within the prostate) and occasionally a secondary index lesion will determine the biological potential of the cancer. Bott et al[7] reported that the index lesion comprised 73% of tumor volume in a total of 374 tumor foci examined. This has led to considering a more preservative approach to treating prostate cancer, including hemi-ablation (half-gland treatment) and focal ablation.[8] Several diagnostic modalities are being investigated to improve the selection of candidates for focal therapy.

Three-dimensional pathological mapping (3DPM) of the prostate gland has been proposed as a method to stage patients prior to focal therapy. In a study of 140 patients, 3DPM of the prostate gland was superior in detecting clinically significant prostate cancer compared to standard transrectal ultrasound (TRUS)-guided biopsy.[9] The use of 3DPM of the prostate gland allowed precise location of the cancer for focal ablation. Sensitivity of the repeated TRUS biopsy in this study was 34%, with a false-negative rate of 52%. All cancers detected by the standard TRUS biopsy were also detected on 3DPM biopsies. Another study by Falzarno et al[10] showed a 10% correlation between the unilaterality of cancer detected by TRUS with unilateral cancer in the final pathological finding.

Another modality assisting with risk estimation is multiparametric prostate magnetic resonance imaging (MRI). Turkbey et al[11] reported that multiparametric MRI has a positive predictive value of 98% to 100% and 68% sensitivity for detecting prostate cancer tumors > 5 mm in diameter. A study by Rastinehad et al[12] reported 94% sensitivity for lesions in the peripheral zone of the prostate, with 99% specificity using multiparametric MRI. MRI/ultrasound fusion-guided biopsy is a more recent imaging modality that is under investigation. Pinto et al[13] reported a detection rate of 89.5% using MRI/ultrasound fusion-guided biopsy.

Two newer promising modalities are histoscanning and real-time elastography. Prostate histoscanning incorporates spectral analysis and pattern recognition to detect cancer lesions. Simmons et al[14] reported 90% sensitivity for cancer volume ≥ 0.20 mL and 72% specificity using histoscanning. Real-time elastography utilizes ultrasound and the compression nature of soft tissue to detect the index lesion. Walz et al[15] reported 58.8% sensitivity and 43.3% specificity in locating the index lesion when using elastography alone. However, combining elastography and data from 12-core biopsies increased the sensitivity and specificity of locating the index lesion to 84.9% and 48.4%, respectively.

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