Neuroendocrine Cancer of the Prostate Metastatic

Neuroendocrine cancer of the prostate metastatic is a rare and aggressive form of prostate cancer that can develop when the disease spreads beyond the prostate gland and becomes resistant to hormone treatments.

Table of contents

• What is Neuroendocrine Prostate Cancer
• The Prostate Gland
• How This Cancer Develops
• How Common It Is
• Key Characteristics of the Disease
• Outlook and Survival
• Treatment Approaches

What is Neuroendocrine Prostate Cancer

Neuroendocrine prostate cancer (NEPC) is an aggressive type of cancer that affects the prostate, a gland found only in men. This form of cancer is very rare, representing less than 2% of all prostate cancers^[2]. The term neuroendocrine refers to special cells in the body that have characteristics of both nerve cells and hormone-producing cells.

Approximately 1% of all cells within the prostate gland are neuroendocrine in origin, meaning they are naturally present in small numbers^[2]. When cancer develops from these cells, or when regular prostate cancer cells begin to behave like neuroendocrine cells, a particularly aggressive form of disease can emerge.

The Prostate Gland

• Prostate
• Bladder
• Urethra
• Rectum

The prostate is a small gland about the size of a walnut that sits between the bladder and the penis, just in front of the rectum^[2]. The urethra, which is the tube through which urine passes, runs through the prostate. The prostate produces a fluid called seminal fluid, which helps to feed and protect sperm. During ejaculation, the prostate releases this fluid into the urethra, where it mixes with sperm and is expelled through the penis as semen.

How This Cancer Develops

Neuroendocrine prostate cancer can develop in two distinct ways. The first is called de novo NEPC, which means the cancer starts as a neuroendocrine cancer from the beginning, without any previous history of regular prostate cancer^[2]. However, this form is quite rare.

More commonly, neuroendocrine prostate cancer develops in the later stages of disease in men who initially had regular prostate cancer, particularly in cases of castration-resistant prostate cancer^[1]. Castration resistance means the cancer continues to grow even when hormone treatments have lowered testosterone levels to very low amounts. This transformation occurs through a process called lineage plasticity, where prostate cancer cells adapt and change their behavior as a way to survive treatment^[1].

When prostate cancer transforms into neuroendocrine cancer, the cells lose their dependence on male hormones. This is shown by a decrease in important markers like androgen receptor (AR), PSA (prostate-specific antigen), and PSMA (prostate-specific membrane antigen) in the tumor^[1]. These changes make the cancer much more difficult to treat with standard hormone therapies.

Research has identified that loss of certain protective genes, specifically RB1 and TP53, plays a key role in allowing this transformation to occur^[1]. Additional changes in the way genes are controlled, involving processes like DNA methylation and the activity of a protein called EZH2, further drive the cancer’s growth and spread.

How Common It Is

Recent research has shown that neuroendocrine prostate cancer is more common than previously thought in men with advanced disease. In one important study, nearly one in five men (approximately 17%) with metastatic prostate cancer that had become resistant to hormone therapy developed this aggressive subtype^[8]. This finding suggests that testing for this subtype should be considered more broadly in men with advanced prostate cancer.

The frequency of finding neuroendocrine cancer can reach up to 15-20% in men with castration-resistant prostate cancer who have been treated with powerful hormone-blocking drugs like abiraterone or enzalutamide^[10].

Key Characteristics of the Disease

Neuroendocrine prostate cancer has several distinguishing features that separate it from typical prostate cancer. When examined under a microscope, the cancer cells appear different: they are smaller and more crowded together compared to the more common form of prostate cancer called adenocarcinoma^[8].

One challenge with neuroendocrine prostate cancer is that it can be difficult to diagnose accurately without expert review of tissue samples under a microscope^[2]. Because neuroendocrine cells are normally present in small numbers in the prostate, doctors must determine not only how many neuroendocrine cells are present in a sample, but also whether they are cancerous and how many there are compared to regular prostate cancer cells.

This form of cancer is usually associated with aggressive disease and is more likely to be classified as a neuroendocrine carcinoma rather than a slower-growing neuroendocrine tumor^[2]. Unlike typical prostate adenocarcinomas, neuroendocrine prostate cancers often produce lower levels of prostate-specific antigen and have less hormone signaling activity^[8].

Outlook and Survival

The outlook for men with metastatic neuroendocrine prostate cancer is generally poor compared to other forms of prostate cancer^[1]. This is partly due to late diagnosis and a lack of highly effective treatments specifically for this subtype.

Research has shown that men whose metastatic tumors consist entirely of the neuroendocrine subtype have shorter survival times compared to men with typical adenocarcinoma. In one study, men with adenocarcinoma lived a median of 44.5 months after developing metastatic castration-resistant disease, while those with neuroendocrine features lived a median of 36.6 months^[8].

The aggressive nature of this cancer, combined with its resistance to standard hormone treatments, makes it a particularly challenging disease to manage. However, ongoing research is working to identify better treatment options and strategies for earlier detection.

Treatment Approaches

Treatment for neuroendocrine prostate cancer differs from standard prostate cancer treatment. Because these cancers do not respond well to hormone-blocking therapies, different approaches are needed.

The standard first-line treatment for neuroendocrine prostate cancer typically involves platinum-based chemotherapy, which is a type of powerful drug treatment^[11]. While this treatment can be effective initially, the response often does not last long, and finding effective treatments after the first-line therapy stops working remains a significant challenge.

Second-line treatments after platinum-based chemotherapy has been tried include various options, but results have generally been disappointing. Studies have shown that treatments using platinum combined with etoposide or docetaxel as second-line therapy had poor outcomes, with the cancer starting to grow again after 3 months or less^[11]. Other drugs like amrubicin and irinotecan have also been tried, but their effectiveness has been modest, with responses lasting less than 6 months.

There is some encouraging news for certain patients. Men whose neuroendocrine prostate cancer has specific genetic changes involving genes that repair DNA (called homologous recombination repair gene alterations) may benefit from drugs called PARP inhibitors^[11].

Several clinical trials are currently investigating new treatment approaches, including drugs that work with the immune system (immune checkpoint inhibitors), molecularly targeted agents, and PARP inhibitors^[11][10]. These studies aim to find more effective ways to treat this challenging form of cancer.

Researchers are also working to better understand the biological processes that lead to neuroendocrine transformation, with the hope that this knowledge will lead to strategies to prevent the transformation from happening in the first place or to catch it at an earlier, more treatable stage^[1][10].