Until about 10 years ago, conventional prostate cancer treatments were based on the assumption that prostate cancer is a multifocal disease. All conventional treatment modalities (surgery, radiotherapy, and thermal ablation) were “radical” because they were directed at the removal or destruction of the whole gland. Such treatments, however, put urinary and sexual function at risk, potentially diminishing patient quality of life on a short-to-long term basis. Within the last decade, treatments were developed to target just to the tumor, or the side of the gland containing tumor(s), with the goal of effective cancer control while substantially reducing the risk of side effects. Clinically, these are termed “sub-radical” treatments; they are referred to as targeted, tissue preserving, or focal treatment. Urological societies in the U.S. and abroad have defined criteria for focal treatment of prostate cancer as a standard of care.[i],[ii]
Several factors are behind the development of sub-radical treatments. The detection, diagnosis and treatment of prostate cancer have been influenced by the following:
- A higher percentage of men than previously thought have tumors that qualify for tissue preserving (sub-radical) treatment. Qualifications may include (1) unifocal disease, (2) unilateral disease (one side of the gland only), (3) bilateral/bifocal with at least one neurovascular bundle avoided, or (4) bilateral/multifocal with one dominant index lesion and secondary lesions with Gleason ?3+3 and cancer core involvement ?3mm.[iii]
- Surgery is neither adaptable nor desirable for performing a sub-radical treatment. As for radiation, there are clinical studies on “targeting” radiation just to the tumor. However, all radiation has some scatter, making it impossible to selectively spare nearby healthy tissue. Finally, radiation is not comparable to the immediate tumor destruction that occurs with thermal ablation (extreme heat or cold); radiation requires exposure over time to damage the DNA of cancer cells, so it is not possible to track in real time the tissue changes in the targeted area. The true results of radiation are not known for several months after treatment ends.
- Genomic testing, increasingly available, reveals that among the differing cell lines of prostate cancer, not all are likely to evolve into deadly aggression levels. Thus, tumors can be classified as significant (likely to become life-threatening) and insignificant or indolent (unlikely to pose a threat).[iv] Patients deemed to have insignificant prostate cancer may be recommended for Active Surveillance (defer treatment until it becomes necessary) as an alternative to radical treatment with its attendant risks of urinary and sexual side effects. In most cases, candidates for Active Surveillance are also candidates for focal therapy.
- Advances in imaging have lead to an increase in early detection; in turn, this has led to a downward migration in the stage at which prostate cancer is diagnosed.
- Image-guided thermal ablation technologies that work for targeted tumor ablation have reached a development level where they are demonstrated safe, relatively inexpensive to deliver, and have reproducible results thanks to sophisticated planning, safety and feedback systems (reduced operator dependence). These include cryoablation (freezing), High Intensity Focused Ultrasound (HIFU; heat ablation using sonic energy), and Focal Laser Ablation (heat ablation using light energy).
- Patients are actively seeking a “middle ground” treatment that reduces the risks of radical treatments and also alleviates the psychological burden of Active Surveillance.
- Economic pressures caused by rising healthcare costs, and the high price levels of robotic and radiation devices, are motivating the evolution of less costly treatments that are still effective.
- Published articles on the efficacy and low side effect profile of focal cryoablation make a compelling case for the long term cancer control of focal treatment when patients are properly qualified for it.[v],[vi] Laser ablation uses light energy to generate lethal heat, which is as effective at cell destruction as a lethal freeze, though with different mechanisms of cell death.
Focal Laser Ablation (FLA) – A growing body of published clinical literature now points to 3T Multiparametric MRI as a superior imaging modality that can be applied to the prostate gland for detection of tumors, targeting of biopsies into the tumors, and guidance/real time monitoring of treatments that can be done under the magnet. In fact, MRI is the foundation of Focal Laser Ablation (FLA) due to its accurate identification of the size, shape and location of prostate tumors. Real-time MRI guidance allows for:
- Accurate placement of the applicator and laser fiber,
- Identification of temperatures and ablation as it is occurring, giving the clinician a very high degree of confidence that the desired region has been effectively destroyed,
- Immediate depiction of post-treatment tissue change, allowing further verification of ablation at the time of treatment.
- Longer-term follow-up to monitor for cancer recurrence in other areas of the prostate.
Now that the groundwork is well established for focal therapy, patients who are qualified for a targeted treatment approach have several delivery systems to choose from. Patients should take into account the superiority of real-time MRI guidance for focal therapy, and the fact that FLA is the most widely used MRI-guided form of ablation. Early FLA results indicate the lowest risk of urinary and sexual side effects of all focal treatments. The Sperling Prostate Center has the longest experience with MRI-guided FLA, having successfully treated more than 500 patients. We are proud to be the leader in this treatment, when the time for it is ripe.
[i] Ahmed H, Pendse D, Illing R, Allen C et al. Will focal therapy become a standard of care for men with localized prostate cancer? Nat Clin Pract Oncol CME. 2007;4(11):632-642.
[ii] De la Rosette J, Mouraviev V, Polascik T. Focal targeted therapy will be a future treatment modality for early stage prostate cancer. Eur Urol Suppl 2009;8:424-32.
[iii] Singh PB, Anele C, Dalton E, Barbouti O et al. Prostate cancer tumour features on template prostate-mapping biopsies: implications for focal therapy. Eur Urol. 2013 Oct 6. pii: S0302-2838(13)01039-7. doi: 10.1016/j.eururo.2013.09.045. [Epub ahead of print]
[iv] Johnstone PAS, Rossi PJ, Jani AB, Master V. ‘Insignificant’ prostate cancer on biopsy: pathologic results from subsequent radical prostatectomy. Prostate Cancer Prostatic Dis. 2007;10(3):237-241.
[v] Bahn D, Abreu A, Gill I, Hung A et al. Focal cryotherapy for clinically unilateral, low-intermediate risk prostate cancer in 73 men with a median follow-up of 3.7 years. Eur Urol. 2012 Jul;62(1):55-63.
[vi] Onik G, Vaughan D, Lotenfoe R, Dineen M, Brady J. The “male lumpectomy”: focal therapy for prostate cancer using cryoablation results in 48 patients with at least 2-year follow-up. Urol Oncol. 2008 Sep-Oct;26(5):500-5. doi