Prostate Cancer

What is Prostate Cancer

Prostate cancer begins when cells in the prostate gland start to grow out of control. The prostate is a gland found only in males. It makes some of the fluid that is part of semen.

The prostate is below the bladder (the hollow organ where urine is stored) and in front of the rectum (the last part of the intestines). Just behind the prostate are glands called seminal vesicles that make most of the fluid for semen. The urethra, which is the tube that carries urine and semen out of the body through the penis, goes through the center of the prostate.

The size of the prostate can change as a man ages. In younger men, it is about the size of a walnut, but it can be much larger in older men.

TYPES OF PROSTATE CANCER

Acinar adenocarcinoma

Adenocarcinomas are cancers that develop in the gland cells that line the prostate gland. They are the most common type of prostate cancer. Nearly everyone with prostate cancer has this type.  

Ductal adenocarcinoma

Ductal adenocarcinoma starts in the cells that line the ducts (tubes) of the prostate gland. It tends to grow and spread more quickly than acinar adenocarcinoma.

Transitional cell (or urothelial) cancer

Transitional cell cancer of the prostate starts in the cells that line the tube carrying urine to the outside of the body (the urethra). This type of cancer usually starts in the bladder and spreads into the prostate. But rarely it can start in the prostate and may spread into the bladder entrance and nearby tissues.

Squamous cell cancer

These cancers develop from flat cells that cover the prostate. They tend to grow and spread more quickly than adenocarcinoma of the prostate.

Small cell prostate cancer

Small cell prostate cancer is made up of small round cells. It’s a type of neuroendocrine cancer.

Other rare cancers

Other rare cancers can develop in the prostate, these include:

Cause of Prostate Cancer

On a case-by-case basis, doctors cannot say with certainty what causes Prostate Cancer, but experts generally agree that diet contributes to the risk. Men who consume large amounts of fat — particularly from red meat and other sources of animal fat cooked at high heat —  may be more likely to develop advanced prostate cancer.  The disease is much more common in countries where meat and dairy products are dietary staples than in countries where the basic diet consists of rice, soybean products, and vegetables such as broccoli, cauliflower, cole slaw, or sauerkraut.

Researchers do not know exactly what causes prostate cancer. But they have found some risk factors and are trying to learn just how these factors might cause prostate cells to become cancer cells.

On a basic level, prostate cancer is caused by changes in the DNA of a normal prostate cell. DNA is the chemical in our cells that makes up our genes, which control how our cells function. We usually look like our parents because they are the source of our DNA. But DNA affects more than just how we look.

Some genes control when our cells grow, divide into new cells, and die:

  • Certain genes that help cells grow, divide, and stay alive are called oncogenes.
  • Genes that normally keep cell growth under control, repair mistakes in DNA, or cause cells to die at the right time are called tumor suppressor genes.

Cancer can be caused by DNA mutations (or other types of changes) that keep ontogenesis turned on, or that turn off tumor suppressor genes. These types of gene changes can lead to cells growing out of control.

DNA changes can either be inherited from a parent or can be acquired during a person’s lifetime.

Treatment in Nuclear Medicine

 Lu PSMA (LUTETIUM-PROSTATE SPECIFIC MEMBRANE ANTIGEN) THERAPY?

Lu177 PSMA Therapy is a treatment for patients with prostate cancer, especially those who have become refractory to conventional therapy. Lutetium PSMA therapy helps to slow down the growth of the cancer cells, reduce the size of the tumors and most importantly improve the quality of life of the patients by reducing the pain caused by the cancer.

WHAT IS PSMA?

Many prostate cancers, in particular those that have spread or become resistant to hormonal therapies, express a unique receptor on their cell surface called Prostate Specific Membrane Antigen (PSMA). When Prostate Cancer metastasizes i.e. spreads to other parts of the body, the PSMA receptor is expressed over the sites of metastases as well.

PSMA is an excellent target for both Radionuclide Imaging & Therapy of Prostate Cancer for several reasons:

  • It is expressed in practically all Prostate Cancers in all stages of the disease
  • It gets unregulated in hormone refractory or metastatic disease
  • It is an integral cell membrane protein and not released into circulation
  • The PSMA is internalized after Antibody Binding (Receptor-mediated Endocytosis).
HOW DOES Lu PSMA THERAPY WORK?

Lutetium-177 is a radioactive substance that emits beta radiation, a destructive kind of radiation. Lutetium-177 is bound to a small peptide which attaches to the PSMA receptor expressed on the cancer cell surface. The Lutetium 177 – PSMA complex, thus attached to the prostate cancer cell, then emits killing radiation causing cell death of the cancer cell. Since the penetration of the emitted beta particle is very small, the surrounding normal cells are spared.

HOW IS THE THERAPY DONE?

Lu177 PSMA is administered intravenously. The patient is admitted to the hospital for 24 hours. A kidney function scan called a MAG3/EC scan is done prior to the administration of the Lu177 PSMA. The patient is usually hydrated by intravenous fluids before and after the administration of the Lu177 PSMA over a period of 24 hours.

WHAT ARE THE SIDE EFFECTS OF Lu PSMA THERAPY?

Lu177 PSMA is well tolerated. The most common side effects are a slightly dry mouth, fatigue and nausea. There may also be a slight fall in the white blood cells and platelets about 2 – 3 weeks after the Lu177 PSMA administration. Usually, these side effects are mild and transient and recover spontaneously without any active treatment. The chances of serious or life-threatening complications are extremely rare

WHAT IS THE RESPONSE RATE WITH Lu PSMA THERAPY?

The response rates of Lu177 PSMA depend on the tumor biology of prostate cancer, the initial Gleason Score, the extent of disease and the responses to prior therapies. Typically, more than 70% of patients demonstrate a reduction in S. PSA and shrinkage of tumors following Lu177 PSMA therapy. Nearly all patients demonstrate a reduction in pain and an improvement in global health by the second dose of therapy.

WHEN WOULD THE DOCTOR CONSIDER USING THIS THERAPY?

Lu PSMA Therapy is a very specific therapy and is used for managing metastatic Prostate Cancer or when Prostate Cancer is no longer responsive to other types of treatment.

The therapy is offered to patients of Advanced Castration-resistant Metastatic Prostate Cancer with evidence of tumor progression are eligible for this therapy. Cancer progression may manifest as:

  • Rising Serum PSA levels
  • Increase in the size or number of the metastatic lesions on CT/MRI or Ga68 PSMA scans
  • Increasing pain or other worsening symptoms due to the disease

Lu177 PSMA Therapy cannot be given to patients in case of

  • Severe renal insufficiency
  • Severe hematological compromise
WHAT ARE THE TREATMENT SCHEDULES WITH Lu PSMA THERAPY?

Most patients undergo three-four treatment cycles at intervals of 8-12 weeks. The number of cycles and the interim duration may vary between individuals depending on the response and interim assessments. The average dose of Lu PSMA Therapy administered is in the range of 5.5-11GBq per treatment and the doses are based on pre-treatment dissymmetry (Dissymmetry is the measurement, calculation and assessment of the ionizing radiation dose absorbed by the human body).

For treatment, the patient is admitted in the hospital in a Specialized High Dose Radioisotope Therapy Unit for monitoring and radiation protection.

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