By: Dan Sperling, MD

In the ever-evolving world of medicine, technical advances in biological knowledge, imaging and equipment have made it increasingly possible to treat diseased tissue with minimal to no impact on surrounding healthy tissues. For example, it is both preferable and feasible to treat very small kidney cancers by surgically removing just the portion of the gland containing the tumor, in order to preserve kidney function. Another way to preserve organ function is to destroy tumors by means of minimally invasive thermal ablation (extreme cold or heat). Thus, depending on the location, size, extent and aggressiveness of a cancerous tumor, treatments range from radical (treat the entire organ, leaving no functional tissue behind) to regional to focal.

Until recently, prostate cancer was assumed to be multifocal with all cells being of the same potential danger. As such, the gold standard of treatment became radical prostatectomy, often leaving patients with side effects that compromised not only prostate function (no semen) but also urinary and erectile function. To avoid this situation, the option of active surveillance (AS) has been proposed for patients with early stage, low risk disease. The clinical rationale for AS comes from evidence that not all prostate cancer is equal, that is, many experts now agree that microscopic Gleason 6 disease is insignificant (unlikely to progress). However, AS requires monitoring so that a treatment window is not missed should the cancer become more aggressive. If and when it does, patients again face the prospect of a radical treatment with the attendant risks of lifestyle impairment. In this situation, a focal treatment may offer excellent cancer control with far less risk of urinary and sexual damage.[i]

Multiparametric MRI (mpMRI) offers the utility of detecting the presence of a significant tumor (index lesion) whether or not there are multiple foci of insignificant disease. A 2013 study out of the National Cancer Institute (NIH, Bethesda, MD) demonstrated how useful advanced imaging can be in identifying candidates for focal treatment of localized prostate cancer.[ii] The purpose of the study was to determine if imaging could accurately distinguish higher grade prostate cancer from insignificant cancer. The authors analyzed data on 583 men who had mpMRI prior to two types of biopsy:

1. MRI/ultrasound fusion guided biopsies targeted to areas seen by mpMRI that were scored as low, moderate or high suspicion for prostate cancer based on a validated scoring system, and
2. Systematic TRUS guided biopsies (12 samples)

The lesions with the highest suspicion score were correlated with the pathology results of the fusion guided (targeted) biopsies to assess the accuracy of the imaging. Significant correlations between mpMRI suspicion score and presence of prostate cancer were verified. The strongest associations were with Gleason 7 or greater cancer.

The findings of the National Cancer Institute study strongly suggest that mpMRI can play a useful role not simply in the early detection and first-time diagnosis of prostate cancer, but also assisting AS patients and their physicians in monitoring for the eventuality that Gleason 6 cancer progresses to a point where treatment is necessary. At that time, given the ability of advanced, high resolution multiparametric imaging to help determine the location, size and shape of a significant tumor, a patient interested in a focal treatment can rule it in or out, in consultation with doctor. Thus, mpMRI detection of significant cancer has great usefulness for treatment planning.