Prostate cancer is a leading cause of cancer death in U.S. men, second only to lung cancer. During 2008, an estimated 186,320 new cases of prostate cancer will be diagnosed in the U.S. Approximately one in six men will be diagnosed with and one in 34 will die of prostate cancer.1
Once a diagnosis is made, the extent or stage of the disease must be determined before treatment decisions are made. The most critical issue is whether the tumor is confined to the prostate gland itself or extends beyond.
Staging is based upon a combination of the clinical results of the prostate-specific antigen test and its subanalysis such as velocity and density, the Gleason score, a patient's age, imaging such as endorectal coil MRI, and family history.
Localized prostate cancer treatments range from the aggressive radical prostatectomy to active surveillance, or watchful waiting. Selection of treatment is based on a full evaluation of the risks and benefits of all treatment options within the context of the patient's situation. Chief treatment determinants are medical recommendations, patient preferences, and local expertise, including the availability of various treatments.
Major concerns include the possibility of successful treatment of the tumor and the extent of side effects. Given the extreme range of treatment options and concern about side effects, patients and their doctors are giving close scrutiny to new focal and/or minimally invasive treatments as possible alternatives.
These alternative focal treatment options differ from traditional approaches in that they do not treat the entire prostate gland as if it were uniformly filled with cancer. One major driver of alternative treatment approaches, or less than total gland treatment, is the desire to preserve the patient's quality of life. The side effects of traditional prostate surgery and radiation include incontinence, impotence, and rectal damage (from the radiation).
Traditional surgery always involves total gland removal, and radiation treatments deliver uniform doses of brachytherapy and external-beam radiation, for example, to the entire gland. The newer treatment of intensitymodulated radiation therapy (IMRT), however, allows for dose escalation to focal regions.
New radiation planning software now offers so-called dose-painting approaches to tailor dose delivery to only those predefined abnormal regions of the gland. These regions are most commonly MRI-defined. MR-guided brachytherapy, pioneered by D'Amico et al,2 was one of the first "sub-total gland" treatments established for prostate cancer. It uses MR images to outline a subregion of the gland, generally the peripheral zone of the gland as seen on T2-weighted MRI, to define the clinical target volume. Compared with radical prostatectomy, MR-guided brachytherapy is very successful in that it has led to similar outcomes and more favorable quality of life.3,4 Using other radiation approaches such as IMRT can minimize some side effects. Surgical approaches can also be modified to some degree using laproscopic or robotic techniques. These efforts are mainly directed at reducing perioperative morbidity and length of stay in the hospital, however, and early evidence suggests that they require significant expertise and can be associated with significant failure rates.5
Another alternative to conventional prostate treatment that has been in clinical use worldwide for many years is therapeutic ultrasound using focused acoustic energy to cause thermal coagulation deep within the prostate. Parts of the prostate gland can be ablated once a high-intensity ultrasound beam is localized to a small focal point, resulting in individual sonications causing thermal damage, or thermocoagulation. To control the ablation and minimize side effects, a clinician can regulate ultrasound power deposition and other parameters so as to ablate only the intended volume of tissue.
When focused acoustic energy is combined with MRI as the imaging guidance tool, the technique is known as MR-guided focused ultrasound surgery (MRgFUS), but when it is used with ultrasound, the technique is generally known as high-intensity focused ultrasound (HIFU). MR's critical advantage is its ability to provide MR thermometry to allow real-time feedback of therapeutic heating effects during treatment.
