Proton Therapy for Prostate Cancer: An Overview

What Is Prostate Cancer?

Prostate cancer is when the cells in the prostate gland (a part of the male reproductive system) grow and divide continuously, thus harming the prostate and surrounding tissues and organs. The treatment approach for prostate cancer is multidisciplinary, and radiation therapy is one of the treatments. It is advised in patients with localized prostate cancer. It is combined with other treatments like chemotherapy in conditions like advanced metastatic cancers.

What Is Radiation Therapy/ Radiotherapy of the Prostate Gland?

Usage of high-energy beams of rays to kill the cancer cells in the prostate gland is called radiation therapy. Radiation depends on the stage of cancer, and it is of two types, namely:

1. External Beam Radiation Therapy: High beam rays coming from a machine are placed outside the body of the patient, and these rays are targeted toward the prostate. This machine rotates around the target area (prostate), delivering the rays to all sides of the target (prostate) site.

2. Internal Beam Radiation Therapy: Also called brachytherapy, where radioactive substances in the form of seeds or pellets, or tubes are inserted into the prostate so that a large amount of radiation effectively hits the target area without causing any damage to the surrounding tissues.

What Are the Disadvantages of External Beam Radiation Therapy (EBRT)?

• Radiation Proctitis: Injury and damage of the rectum because of radiation; symptoms include diarrhea and bloody stools.

• Radiation Cystitis: Damage to the urinary bladder by radiation leading to incontinence (loss of bladder control), burning sensation, and blood in the urine.

• Erection Problems Leading to Impotence: Sexual life gets compromised.

• Lymphedema: Lymph nodes drain the excess fluid surrounding the prostate into the heart, but when these lymph nodes are destroyed by radiation, excess fluid retains in the pelvic area, causing swelling of the legs.

What Is Proton Therapy?

Proton therapy is a form of external beam radiation therapy. It is non-invasive, where a proton beam directly hits the target cancer cells and damages its DNA (deoxyribose nucleic acid). Thereby cancer shrinks in size, and further growth is stopped. The right radiation dose is delivered to every part of cancerous tissue, killing cancer more effectively and sparing the healthy tissues.

What Is the Time Duration of Proton Therapy?

Photon therapy is advised five days a week, and each day it takes 15 to 20 minutes to deliver the photon beam. Patients are asked to return home after treatment as the recovery time is very less, and most of the patients continue with their routine activities post-treatment. Usually, it is advised for seven to eight weeks depending upon the patient's condition.

How to Prepare a Patient for Proton Therapy?

A prior appointment is given to the patient, and the radiation oncologist will plan for the exact amount of radiation dose, treatment time, and patient position in accordance with the photon beam. On the day of the treatment, the patient is made to lie on the treatment table, and the doctor marks the place where the proton beam hits the body; then, the patient is positioned according to the beam, and positioning devices are placed around the patient to keep the body still during the radiation. No anesthesia is given; the patient can simply walk home post-radiation treatment.

Can Proton Therapy Beat the Side Effects of EBRT in Prostate Cancer?

Yes, proton therapy overcomes the side effects of EBRT because:

1. Prostate cancers are difficult to treat by EBRT because of their location near the sex organs and urinary tract.

2. EBRT affects healthy and non-cancerous tissue on its way to hitting the target site, whereas the proton beam is precise and does not harm the surrounding tissues.

3. If conventional X-ray uses eight beam angles for treatment, proton therapy uses only two beam angles. This is called targeted care.

Does Proton Therapy Work Better Than Photon Therapy in Prostate Cancer?

Both are effective in delivering radiation to the target site. Traditionally photon radiation uses X-rays, which release radiation throughout the beam, causing damage to the structures on the way. Damage could be seen in:

• Bones surrounding the pelvis.

• Rectum, urethra, urinary bladder.

• Intestines.

• Penis, testicles.

Radiation in these areas may cause impotence and incontinence.

Which Is Best Between Proton Therapy and Prostatectomy?

Prostate cancers in the initial stages are treated by prostatectomy (surgical removal of the prostate gland); this is permanent and irreversible and causes infertility and loss of sexual desire in men.

But in proton therapy, the precise proton beam hits the cancer cells in the prostate gland, destroying DNA ( deoxyribose nucleic acid); thus, cancer cells shrink in size, and further growth is stopped. Proton therapy also carries the same risks as surgery, but the risk is less likely to cause permanent damage.

What Are the Disadvantages of Proton Therapy?

1. It is costly when compared to other types of radiation.

2. It is unavailable in all cancer centers; only certain specialized proton centers have this facility.

3. Due to its cost, some insurance companies will not consider proton therapy.

Pencil Beam Proton Therapy: A more advanced form of proton therapy. It is also called spot-scanning proton therapy; it delivers a single narrow (less than one millimeter) photon beam across the tumor. Delivering the radiation like a paintbrush. It does not use any beam-shaping device.

How Does It Work?

It works by sending rapid pulses, where a proton beam enters every part of the tumor, delivering a fixed amount of radiation. Delivering of the proton beam first starts from the deeper layers, followed by layer by layer, and completes until the whole tumor is covered. It is highly effective, and the proton beam takes only a few minutes to reach the target area.

What Are the Advantages?

1. Results appear quickly when compared to conventional methods of radiation.

2. Surrounding tissues are saved from the ill effects of radiation.

3. The whole prostate gland will receive the photon radiation without any quality compromise.

4. The painting mechanism in the pencil beam treats even the prostate cancer cells that are placed at depth.

Conclusion:

Proton therapy is more effective in treating prostate cancer when compared to the traditional method of radiation, by minimizing the harm to the surrounding tissues.