BACKGROUND: In the United States in 2012, an estimated 28,170 men died from prostate cancer and there were 241,740 new cases. (Source: www.cancer.gov) Prostate cancer starts in the prostate. The prostate is a small structure that wraps around the urethra and makes up part of the male reproductive system. Prostate cancer is the most common cause of death in men over 75 years old. A common problem in almost all men is an enlarging prostate, called benign prostatic hyperplasia (BPH). It does not increase the risk of developing prostate cancer, but it raises PSA blood test results (a screening for men for prostate cancer). PSA testing is responsible for detecting the cancer before symptoms occur. (Source: www.ncbi.nlm.nih.gov)
SYMPTOMS: Symptoms usually do not occur until prostate cancer is in a later stage. Symptoms relating to prostate cancer can also be caused by other prostate problems, including delayed or slowed start of urinary stream, dribbling or leaking of urine (usually after urinating), slow urinary stream, blood in the urine or semen, straining when urinating or not being able to empty out all of the urine, and bone pain or tenderness usually occurring in pelvic bones and lower back. If prostate cancer is suspected, then the doctor will have to do a biopsy to know for sure. (Source: www.ncbi.nlm.nih.gov)
TREATMENT: Treatment options have many factors to consider. For early-stage prostate cancer doctors recommend surgery, called radical prostatectomy, or radiation therapy, including brachytherapy and proton therapy. If the patient is older, then the doctor might recommend just monitoring the cancer with PSA tests and biopsies. In cases where the cancer has spread, treatment can include surgery, chemotherapy, and hormone therapy to reduce testosterone levels. (Source: www.ncbi.nlm.nih.gov)
NEW TECHNOLOGY: The problem with traditional treatment is the reoccurrence issue. It happens to about 30% of prostate cancer patients. A new therapy in its phase 3 trials, ProstAtak, might change the way prostate cancer is treated. The study is designed to compare two treatments, ProstAtak with external beam radiation therapy and Placebo with external beam radiation therapy. An estimated 700 people are involved in this study. In phase II trials, the rate of recurrence was reduced from 30% down to 10%. Based on an innovative technique called gene transfer technology, ProstAtak is used along with standard radiation therapy. The basic idea is to “jump-start” the body’s own immune system so it can detect and kill remaining or recurring cancerous cells. If the outcome of the study is positive, then ProstAtak will most likely be approved for early stage prostate cancer treatment. (Source: www.drstevensukinurology.com)
Mark Buyyounouski, MD, MS, Associate Professor of Radiation Oncology and Director of Clinical Research at the Fox Chase Cancer Center, talks about a new and exciting treatment for prostate cancer.
Can you tell me what is so exciting about ProstAtak?
Dr. Buyyounouski: ProstAtak is a very exciting new treatment because it’s an entirely different way to treat prostate cancer. ProstAtak is an adenoviral vector that expresses a herpes simplex virus thymidine kinase gene that helps not only kill prostate cancer within the prostate, but stimulates an immune response throughout the body to kill prostate cancer in the event that it spreads.
It actually works with the body’s immune system then?
Dr. Buyyounouski: Right. The problem for most patients is that prostate cancer is below the radar. It’s growing within their body and their prostate, but the immune system hasn’t yet detected it to kill it itself. By combining ProstAtak and radiation together we hope to bring the prostate cancer into the patients’ radar to ramp up the immune system to help better kill the cancer, not only in the prostate but throughout the body.
This is to prevent recurrence and it’s for later stage prostate cancer, correct?
Dr. Buyyounouski: This treatment is to prevent recurrence but it’s intended for patients with early stage prostate cancer. So that’s the additional advantage of ProstAtak, this isan immunotherapy intended for early stage patients before there’s definite evidence of spreading. The study targets patients who have about a one in four to a one in two chance of having prostate cancer recur in the future. We do intensive studies in the beginning when we diagnose patients to make sure there’s no evidence of spreading, but we know, like weeds in a garden, if there are one or two cells that have escaped they could come back years from now. How ProstAtak may help these patients is by amping up their immune system to help better detect prostate cancer in the prostate and throughout the body in order to kill it.
So with traditional therapy you have surgery or radiation; can you talk a little bit about the traditional therapies and some of the misconceptions?
Dr. Buyyounouski: Conventional treatment for localized prostate cancer is surgery or radiation. Unfortunately there are misconceptions sometimes that if patients have treatment to their prostate, particularly cutting the prostate out with surgery, that means the cancer will never come back. Unfortunately the prostate cancer still can come back because many prostate cancers have already spread by the time we find them.
So that’s the big concern?
Dr. Buyyounouski: The big concern is that there can be prostate cancer cells that have spread to lymph nodes or bones that’s beyond our detection with conventional scans.
ProstAtak helps in that way to prevent recurrence and to help it from spreading, right?
Dr. Buyyounouski: ProstAtak works by a process called gene mediated cytotoxic immunotherapy, which helps stimulate T-cells throughout the body to better find cancer cell antigens in order to fight them, whether they are in the prostate, in lymph nodes, or in bones.
So if you were explaining this to your son, how would you explain it?
Dr. Buyyounouski: Conventional treatment for clinically localized prostate cancer is to radiate the prostate and the immediate area surrounding it. It’s a highly effective treatment that in the vast majority of circumstances can cure prostate cancer. However, for many patients, about one in four, prostate cancer can come back. The problem there is radiation only works where you point it, and sometimes there are cancers that are too big for the radiation to kill. How ProstAtak may help is by injecting it in to the prostate to better kill the cancer cells within the prostate and to help better stimulate the immune system to fight the cancer itself.
Are there any results back yet from the trial?
Dr. Buyyounouski: There are preliminary results from Phase I and Phase II trials that have demonstrated this drug is safe and appears to be effective in killing prostate cancer. Compared to historical controls there were far fewer recurrences in the Phase II trial, which prompted this fast track Phase III trial comparing radiation alone with radiation and ProstAtak.
What about any side effects?
Dr. Buyyounouski: There are some side effects associated with treatment; they’re mostly fatigue. There can be some low blood counts associated with the pro-drug that is used, Valacyclovie. Then the typical radiation type side effects, which are largely due to inflammation. They may need to increase daytime urinary frequency, urgency, or burning with urination. That’s easily addressed with over the counter anti-inflammatories.
The side effects have been minimal?
Dr. Buyyounouski: Yes.