Notes for Commentary: Low Risk: While the observations on the interactive graph are pertinent to the results of treatment, an individual decision for a particular treatment can be influenced by multiple factors. We strongly encourage scheduling consultations with Prostate Cancer Doctors specializing in the fields of Surgery, Brachytherapy and Radiation Oncology. Discussions with an expert in Medical Oncology can help you obtain a balanced perspective of the pros and cons surrounding each treatment.
Overall, 80% of all Low Risk patients will do well with any treatment. While it appears on the charts, that Brachytherapy does the best overall, it is apparent that most patients can do well with any treatment. Therefore, for cancer control purposes, we advise most patients that they cannot make a bad decision. However, note that there is a slight difference in results. Why does Brachytherapy appear to do slightly better in PSA control than external beam or surgery? The difference may lie in the nature and capabilities of each treatment to address all of the cancer.
The primary reason surgery fails in Low Risk prostate cancer is that disease is just beyond the margin of the surgery, which a pathologist can recognize after surgery, or can be suspected when the PSA rises after surgery. Despite some statements by surgeons, it is not possible to see this microscopic disease at the time of surgery and to make a decision to take out more surrounding tissue, such as nerves, at the time of surgery. This determination is difficult even with the abilities of the robotic microscope. From the data, it is apparent that, with low risk disease, the surgeon will leave cancer behind 15-20% of the time and, therefore, you will likely need post-operative radiation 15-20% of the time. Note that the charts indicate robotic surgery offers no real improvement in cancer control over standard radical prostatectomy.
Whether the surgery is an open radical or robotic radical prostatectomy, almost all surgeries done for low risk disease are nerve sparing. The risk of disease outside the gland with low risk disease, as predicted by the Partin Tables*, ranges from 6-28%. The majority of this is disease that penetrates beyond the edge of the capsule called capsular penetration or sometimes extra-prostatic extension. You can determine your risk of lymph node, capsular penetration and seminal vesicle involvement from the Partin Tables*.
There are several forms of external beam radiation. IMRT (Intensity Modulated Radiation Therapy), Protons, Tomotherapy and Cyberknife. IMRT is the most common, with only a few long term studies for the other treatments. Patients should be aware that just because a therapy is new does not make it better. All of the external beam treatments give very similar biological doses (75-81 Gy) and, therefore, the results are also similar. The area treated is also similar. This area includes the prostate and a small margin. As can be seen in the charts, external beam treatments do well for approximately 80% of the patients. Many years of study will still be required to ultimately determine whether any type of external beam treatment will actually be better than the others.
External radiation does a good job of treating the prostate and the area immediately around it, where cancer can spread. The reason the external radiation fails in some low risk disease is likely that the dose delivered is not sufficient to control the disease in the prostate itself. The external dose given to the prostate by external beam techniques is limited by the structures surrounding the prostate, primarily the rectum, bladder and hips. While techniques have been developed to minimize these areas receiving high doses, it is difficult to give doses beyond 75-81 Gy equivalent doses without a higher risk of rectal, bladder and hip injury.
Seed Implantation Alone/Brachytherapy
Brachytherapy has a very low local failure rate in the Low Risk setting. Local failure is reported to be less than 1% in reported series. The reason is the dose delivered to the gland and tumor is considerably higher than external beam techniques. The dose with seeds is 120-145 Gy compared to 75-81 Gy for external beam. The reason seeds can deliver a higher dose to the cancer is that the seeds are placed directly into the gland and tumor. The dose from the seed falls off rapidly, resulting in lower doses to the bladder, rectum and hips than external radiation. Typical seed implant techniques also include the area where the cancer spreads and the planning for an implant always includes the area around the nerve (extracapsular disease). Reports on cancer spread beyond the gland have shown that disease is less than 3 mm from the gland in 98% of these low risk situations. By including a typical margin of 5-10 mm, the extra prostatic disease is covered by the doses from seeds. Therefore, seed implantation may do slightly better overall than external beam because it gives more dose to control the cancer in the prostate, and may do better than surgery, (which has excellent local control), because seed implantation is designed to control the disease beyond the gland as well.
External Beam Radiation and Seed Implantation
A number of studies have included the addition of external beam radiation (EBRT) to seed implantation for Low Risk disease. The addition of external beam radiation is controversial and typically only recommended for low risk patients with a large number positive biopsies. The rationale for the external beam radiation in this setting is to cover disease that may have spread beyond the implant margin. Most patients will not need this additional treatment. If EBRT is recommended, it is generally because of a large number of positive biopsies or for technical reasons to cover areas not possible by an implant. The cancer control results are similar to implant alone and excellent for this approach.
* Partin Tables – The Partin Tables use clinical features of prostate cancer – Gleason score, serum PSA, and clinical stage – to predict whether the tumor will be confined to the prostate. The tables are based on the accumulated experience of urologists performing radical prostatectomy at the James Buchanan Brady Urological Institute. For decades, urologists around the world have relied on the tables for counseling patients preoperatively and for surgical planning. Click for more information