By Kalli Spencer
The main goal of focal therapy is the targeted focal destruction of cancer tissue with the preservation of surrounding healthy prostate tissue. There have been conflicting opinions on the definition, but it seems the consensus is "ablation of the dominant or index lesion"1. The principle of targeted therapy has been applied to other cancers such as breast, liver, brain, and thyroid. It represents the middle ground between active surveillance and treatments such as radical prostatectomy and radiation therapy. The reported benefit of focal therapy is the preservation of sexual function and urinary continence. This is because the energy destroying the cancer is focused only on the affected area within the prostate, sparing any injury to nerves running on the outside of the prostate that supply's the external urinary sphincter or the erectile mechanism of the penis.
Over 90% of patients present with cancer in multiple areas within the prostate (multifocal) and only 20-40% have cancer in one area. Despite the multifocal nature of prostate cancer, many cancerous prostates have "a single substantial lesion" (index lesion). It has been proposed that the characteristics of the index lesion predict the behaviour of disease in the rest of the prostate and it's metastatic potential. So by targeting the index lesion in men with low and intermediate-volume prostate cancer it will provide satisfactory oncological outcomes. Patients should have a life expectancy (> 5 years); a performance status of 0/1 and a Gleeson score
Several energy modalities exist to target the cancer including irreversible electroporation, laser ablation, high intensity focused ultrasound (HIFU), cryotherapy, and photodynamic therapy. The rest of this blog will discuss three modalities currently available in Australia: Irreversible electroporation, HIFU, and laser ablation.
Irreversible electroporation
This treatment is delivered using the Nanoknife system with a low-energy direct current to the focal region. The lesion is delineated by needles which are positioned with ultrasound guidance. Electropulses cause complete ablation with no thermal damage. In a cohort study of 112 patients, Professor Phillip Stricker from St Vincent's Hospital found an overall survival rate of 100%, metastasis-free survival of 99%, failure free survival of 97% at three years2. With regard to incontinence, 98% remained pad free and 76% had no change in erectile function. Twelve patients had to have a repeat treatment.
HIFU
Uses ultrasonic waves to initiate cellular damage. 'High-intensity' refers to the power of these sound waves. The ultrasound probe is placed in the rectum allowing real-time visualization of prostatic tissue and also delivering energy to destroy the desired target
area. The procedure can be technically challenging if the prostate has numerous large calcifications. Isolating the focal area is complex and can result in retreatment rates of up to 34%, more researched is required here. Professor Peter Royce from the Alfred Hospital in Melbourne prefers a whole gland approach as reported in his study of 70 men with a 8 year follow up. Failure-free survival was 71.2% at 7 years and 7.1% of men developed metastases with median metastasis-free survival of 75.4 months. Whole gland HIFU preserved urinary continence and demonstrated erectile function approximate to a nerve-sparing radical prostatectomy.
Laser ablation
A laser probe is introduced through the perineum into the prostate under MRI or ultrasound guidance, facilitated using a grid. Once in position, ablation is monitored using the aforementioned imaging modalities, which indicate whether adequate temperatures have been achieved to destroy cancerous tissue. Professor Celi Varol from the Nepean Hospital in his series of 49 patients found a significant PSA drop and MRI improvement at 18 months4. There was no impact on urinary and sexual function. Persistent cancer was found in 10 patients.
Locally access to these therapies is either through a clinical trial or at specific private institutions and may not always be supported by private health funds.
Comparison between treatment modalities is troublesome given the large variation in treatment administration and follow-up protocols in various studies. In general patient requires follow up with PSA monitoring and regular MRIs. Any rise in PSA or suspicious lesion on MRI would warrant a repeat prostate biopsy. At present there is limited consensus on the definition of treatment failure and success.
Many of the trials require longer follow up outcomes. As experience in focal therapy broadens however, extended periods of follow-up data will soon become available which will be useful to create standardised guidelines for many of these treatment approaches in this select patient population.
References:
1. Perera, M., Krishnananthan, N., Lindner, U. Lawrentschuk N. An update on focal therapy for prostate cancer. Nat Rev Urol 13, 641-653 (2016).
2. Blazevski A, Scheltema MJ, Yuen B, Masand N, Nguyen TV, Delprado W, Shnier R, Haynes A, Cusick T, Thompson J, Stricker P. Oncological and quality-of-life outcomes following focal irreversible electroporation as primary treatment for localised prostate cancer: A biopsy-monitored prospective cohort. European Urology Oncology 2020; 3 (3)283-290.
3. Royce PL, Ooi JJY, Sothilingam S, Yao HH. Survival and quality of life outcomes of high-intensity focused ultrasound treatment of localized prostate cancer. Prostate Int. 2020 Jun;8(2):85-90.
4. Al-Hakeem Y, Raz O, Gacs Z, Maclean F, Varol C. Magnetic resonance image-guided focal laser ablation in clinically localized prostate cancer: safety and efficacy. ANZ J Surg 2019; 89(12) 1610-14.
Disclaimer:
Please note that the options discussed in this blog require longer follow-up outcomes and further research into effectiveness. These treatments are not available in all treatment centers.
Please phone our Telenurse team to discuss options that are available to you and your circumstances. PCFA supports innovation and research into treatment options and survivorship and welcomes further research in these areas.
If you would like to discuss your individual treatment options further or require more information and resources about your prostate cancer journey, reach out to us, as help is available:
