Proton Therapy for Prostate Cancer

A Digital Rectal Exam (DRE) is an examination performed via the rectum, which is adjacent to the prostate. A doctor will physically examine the prostate for irregularities in texture, size or shape, including lumps. The DRE is important because it allows the physician to detect whether cancer cells are growing out from the prostate gland, which could indicate a more advanced stage cancer.

Your physician may also perform a PSA test, in which a blood sample is collected and analyzed for PSA, a substance naturally produced by the prostate gland. If a higher than normal level of PSA is found, it may indicate various prostate issues, including infection, inflammation or cancer.

PSA screening is typically recommended for men beginning at age 40. However, you should speak with your general practitioner or urologist to determine the best age for you to start annual screenings.

PSA levels are measured in units called nanograms per milliliter (ng/mL). There is no specific PSA level to conclusively determine whether a man has cancer or not. However, many doctors use a cutoff point of 2.5-4 ng/mL to decide whether a patient needs further testing. If you have an elevated PSA level, your doctor may recommend an ultrasound, MRI or biopsy to determine whether or not cancer is present.

To learn more about what causes PSA levels to increase, watch this section of Provision’s “Prostate Cancer 101” video.

In order to detect prostate abnormalities, a physician may perform a transrectal ultrasound (TRUS), which uses sound waves to take a picture of the prostate. This is done by inserting a probe into the rectum. A TRUS can help detect enlarged prostates or abnormal growths within the prostate.

Magnetic resonance imaging (MRI) uses radio waves and a powerful magnet to look inside the prostate. These images allow a physician to locate both healthy and diseased tissue. A high definition 3 Tesla (3T) MRI uses a stronger magnet to produce even clearer images than a normal MRI.  A 3T MRI can also show a lesion’s density. This is important for doctors to see, because it indicates how far the cancer has spread. As cancerous cells grow and associate with each other, the lesion’s density increases.

The results of a 4Kscore® test give doctors an indication of whether they’ll find clinically significant cancer in the prostate. The data can also help predict whether that cancer may spread to other parts of the body in the future.

While other tests can provide clues to help with diagnosis, a prostate biopsy is the only definitive way to diagnose prostate cancer. During a biopsy, the doctor will use a very fine needle to take small samples of tissue from various parts of the prostate, then examine them under a microscope. A provider typically uses some form of diagnostic imaging to help guide the biopsy. TRUS is the most common imaging method and is usually performed by urologist. An MRI-guided biopsy, however, allows for more precision when drawing tissue samples, resulting in potentially fewer needle sticks. Many providers are now using TRUS fusion, a combination of ultrasound and MRI, to better visualize the prostate.

Based on how aggressive the cancerous cells are, prostate cancer is given a Gleason score, which determines its Grade. A lower Gleason score means the cancer is less aggressive and looks more like healthy tissue. A more aggressive cancer, which will look less like healthy tissue and is more likely to spread, will be given a higher Gleason score.

Gleason scores can range from 1 to 5. As the chart below illustrates, a lesion with small, uniform glands that are well differentiated will get a score of 1. In this case, the cancerous tissue looks similar to normal tissue. As the scores progress, the glands become more irregular and less differentiated. A score of 5 indicates the lesion lacks glands altogether, instead consisting of sheets of cells. This tissue looks very different from normal, healthy tissue.

In order to determine a patient’s final Gleason score, a pathologist will give the cancer two grades – a primary and a secondary score – and add the two together. The primary Gleason score represents the main pattern of glands, while the secondary score other regions within the legion that may look better or worse. It’s important to know your primary and secondary scores, not just the overall Gleason score. This is because not all cancers of the same Gleason score behave in the same manner. The chart below explains how cancers with the same Gleason score can fall into different Grade groups.

To learn more about how a Gleason score is determined, watch this section of Provision’s “Prostate Cancer 101” video.

For cancer in general, Stages 1 and 2 are usually localized, or limited to the original site. Stage 3 typically indicates the cancer has spread to nearby tissue. Stage 4 generally means the cancer has spread elsewhere within the body.

Prostate cancer staging combines clinical factors like a physical exam, PSA level, Gleason score and imaging to determine an alphanumerical score:

During the staging process, your PSA level can help determine your risk factor:

Since prostate cancer staging takes many factors into account, it can be complicated. For further explanation of the stages of prostate cancer, watch this section of Provision’s “Prostate Cancer 101” video.

Just like traditional x-ray radiation, protons treat tumors by directing radiation into the tumor site and destroying cancer cells, preventing them from dividing and growing. However, when protons enter the body, they deposit most of their energy at the tumor site and do not travel any farther, reducing the risk of damage to surrounding tissue and vital organs. This differs from traditional radiation, because x-rays deposits energy before and after the tumor, exposing healthy tissue and organs to unnecessary radiation.

Some traditional x-ray treatments attempt to reduce the impact of this unnecessary radiation by distributing the radiation across many beams. This creates a lower, but larger, dose of unnecessary radiation around the target tumor site. Provision uses a modern form of proton therapy called pencil beam scanning (PBS), which makes the treatment even more precise than conventional proton methods.

Due to proton therapy’s targeted approach, studies have found that prostate cancer patients treated using this method have a significantly reduced risk of side effects. With proton therapy, the rectum and bladder receive much less radiation compared to traditional radiation. This results in a very low risk of long-term side effects, such as incontinence, bowel damage and impotence. Studies have shown a 50% reduction in bowel frequency⁵ and a 25% lower risk of erectile dysfunction.⁶

Patients who use proton therapy for prostate cancer treatment have low rates of cancer recurrence. Researchers reported the percentage of people who are cancer free after five years of follow up:⁴

Low Risk: 99%
Intermediate Risk: 94%
High Risk: 74%

When treating prostate cancer, physicians take steps to keep the rectum out of the radiation field. Minimizing radiation exposure to the rectum decreases the risk or amount of rectal toxicity a patient may experience. A rectal balloon is commonly used to protect the rectum. This balloon-like device is inserted daily prior to treatment, immobilizing the prostate and creating separation from the rectum.

Alternatively, a one-time administration of SpaceOAR™ Hydrogel can be used to protect the rectum. This is administered prior to the beginning of radiation and lasts throughout treatment. The hydrogel space pushes the rectum away from the prostate and the high-dose radiation field. It is injected during a minimally invasive procedure and, once in place, patients typically can’t feel it. SpaceOAR™ Hydrogel is safe and similar to other products used in brain surgery, cardiology and ophthalmology. It remains in place during radiation treatment for several months and is then absorbed and naturally expelled from the body over time.