Prostate Cancer

Prostate cancer is the uncontrolled growth of abnormal cells in the prostate. These abnormal cells divide and accumulate, forming a tumour. The tumour can then grow to invade other tissue, and can also spread to other parts of the body.

It is the third most common cancer among Singaporean men. Many prostate cancers grow slowly and do not cause any symptoms. These usually do not cause serious harm. However, some prostate cancers can grow aggressively and spread quickly, and this may cause serious harm.

Almost all prostate cancers develop from the gland cells – cells that make the prostate fluid that is in semen. This is known as adenocarcinoma.

There are, however, other types of rarer cancers of the prostate. These types include:

• Small cell carcinomas
• Neuroendocrine tumours
• Transitional cell carcinomas

The early stages of cancer often have no symptoms. However, growth of the cancer in the gland may cause these symptoms:

• Frequent urination especially at night
• Difficulty passing urine
• Slowing of the flow of urine
• Pain during urination
• Blood in the urine or semen
• Weak stream of urine

These symptoms could also be caused by other conditions besides prostate cancer. Problems with urination can be caused by benign prostatic hyperplasia – a non-cancerous enlargement of the prostate. It is, however, still important to consult your doctor so that these causes may be treated appropriately.

In later stages of prostate cancer, the following symptoms may be present:

• Bone pain
• Leg swelling
• Loss of appetite
• Weight loss

• Age – risk increases after the age of 50 years
• Men of African descent have a higher risk of developing aggressive prostate cancer and dying from it
• Family history of prostate cancer
• Obesity
• Diet high in fat but low in fibre
• High testosterone levels

Men over the age of 50 years should discuss with their doctor if the benefits and limitations of prostate cancer screening. Men with a brother or father with prostate cancer diagnosed before 65 years old have increased the risk of getting prostate cancer. Therefore, they should discuss with their doctor about starting screening at an earlier age.

There are several tests for prostate cancer.

A digital rectal examination (DRE) allows the doctor to detect any abnormalities in the prostate gland – whether it is the texture, shape or size. A transrectal ultrasound will also allow for the detection of abnormalities in the prostate gland.

A blood sample can be taken to detect the prostate-specific antigen (PSA). This is a chemical that is naturally produced by the prostate gland. A high level of this antigen will alert the doctor to begin further investigations.

Prostate cancer screening usually involves taking a blood sample for PSA, and may be combined with a DRE.

Patients with a high PSA or abnormal DRE may require a prostate biopsy, which involves taking small amounts of tissue from the prostate gland for examination. It checks for the presence of cancer, and also how aggressive it is likely to be (grade).

Once prostate cancer is diagnosed, other tests that help with finding out the stage of the include computerised tomography (CT) scans, magnetic resonance imaging (MRI), PSMA-PET scans and bone scans.

Treatment options for prostate cancer depends on what the stage and grade of the cancer is, and also the age and general health of the individual.

Active surveillance – some prostate cancers grow very slowly. This means it may take many years for any symptoms emerge, but men in good health should be followed up closely by their doctor to lookout for any sign the cancer is turning aggressive.

Treatment is multidisciplinary, personalised and precise and there are a variety of treatment options available. These may include the following, and possibly in combination:

• Surgery – prostatectomy (removal of the prostate)
• Radiation therapy including:
  • External Beam Radiation Therapy
  • Stereotactic Body Radiation Therapy
  • Proton Therapy
  • Radioactive Implants
• Hormone Therapy
• Chemotherapy
• Radionuclide Therapy
• Immunotherapy

Once the diagnosis is made the consultation with an oncologist is essential in order to understand which treatment options are the most suitable. It is advantageous to be seen by an oncologist with subspecialty interest in treating prostate cancer using both drug and radiation therapy for a holistic assessment.

SpaceOAR

Radiation Therapy is an effective curative treatment for Prostate Cancer. Technological advances like Intensity Modulated Radiotherapy (IMRT), Stereotactic Body Radiation Therapy (SBRT) and Proton Beam Therapy (PBT) have allowed high doses of radiation to be more focused on the prostate while avoiding the nearby healthy tissues.

The rectum is located right next to the prostate, so it is inevitable that a very small part of it would still receive high doses of radiation. There is a small risk of bleeding from the back passage, months to years after radiotherapy, because of this. That is where SpaceOAR comes in, literally and figuratively, to make Prostate Radiotherapy even safer.

What is SpaceOAR and how does it work?

SpaceOAR Hydrogel is made from a soft gel-like synthetic material that consists of 90% water and is safe to use in the body.

It is placed in between the rectum and the prostate, increasing the distance between the 2 organs by approximately 1 cm. The space created, essentially pushes the rectum away from the radiotherapy high dose region, vastly reducing high radiation dose to the rectum.

Figure 1: Hydrogel Placement (Boston Scientific, 2022)

The gel will have a fixed shape and size for 3 months, before liquifying and being naturally absorbed and excreted by the body within 6 months.

Figure 2: MRI of a patient with SpaceOAR Hydrogel (Mariados N et al., 2015)

Less exposure to high dose radiation means less risk of long-term side effects from radiation. This has been demonstrated in a clinical trial whereby patients receiving prostate radiotherapy with the SpaceOAR had significantly a 75% reduction in mild and above rectal bleeding compared to those who did not. Notably, there were no cases of moderate and above rectal bleeding in patients who had SpaceOAR (refer to Figure 3)

Figure 3: Results from a clinical trial on the usage of SpaceOAR: Reduction in rectal bleeding (Mariados N et al., 2015)

The SpaceOAR Procedure