This article will cover photodynamic therapy as a treatment for prostate cancer. We will discuss what photodynamic therapy is and consider its impact on prostate cancer patients. We will also discuss its benefits and limitations.

Introduction

Photodynamic therapy is a therapy that involves using molecules that become activated by light to destroy abnormal cells. It can also be used to treat cancers and skin conditions.¹ At the time of writing, photodynamic therapy is an experimental treatment for those with prostate cancer and is actively being assessed in clinical trials.² 

Photodynamic therapy is currently used to treat other cancers such as basal cell carcinoma, lung cancer, and oesophageal cancer in early stages, however, its efficacy in treating prostate cancer is currently unknown.¹ Clinical trials are currently underway to evaluate this treatment strategy in early-stage prostate cancer as it may provide an alternative treatment method for patients. 

Prostate cancer treatment options

Prostate cancer is the most common cancer affecting men in the UK.³ The prostate gland in healthy individuals functions to create the fluid component of semen.⁴ However if cancer develops in the prostate, individuals will experience symptoms of increased need to urinate and feeling that the bladder isn't empty. Symptoms do not generally appear until the cancer is large enough to affect the urethra (the tube that carries urine from the bladder to the penis), therefore tests such as PSA testing and physical examinations are important for diagnosis.⁴ In the UK, it is estimated that 1 man dies of prostate cancer every 45 minutes.³

Typically, at the early stage, prostate cancer requires no treatment and is simply monitored (active surveillance). This is to avoid the risks of surgery and the unnecessary side effects of treatments while the cancer is still small and non-invasive.⁵ 

When treatment is necessary, options include:

• Surgically removing the prostate (radical prostatectomy)
• Radiotherapy
• Brachytherapy (where the radiation dose is delivered directly into the prostate) 
• Hormone therapy
• Cryotherapy (which involves freezing cancerous cells until they die)  
• Chemotherapy

Whilst there are many treatment options for prostate cancer, patients may feel anxious during the active surveillance of their early-stage prostate cancer, and therefore there is a need for non-invasive treatments for early-stage cancers. This is where photodynamic therapy may come in. 

What is photodynamic therapy?

Photodynamic therapy involves using inactive medicines that become activated in the presence of light. Once activated these drugs can destroy the cancer cells. The inactive drugs used in photodynamic therapy are known as photosensitisers, and, when activated by light, release what is known as reactive oxygen species.⁶ Reactive oxygen species are unstable molecules that contain oxygen and cause damage to cells leading to cell death.⁷ It is these molecules that cause the cancer to be destroyed.

The photosensitisers will be administered either systemically or directly to the tumour site. A light source is then applied in a few ways; these can include inserting light-emitting devices into catheters/ endoscopes or placing optical fibres directly into the prostate gland itself.⁶ 

The reactive oxygen species then act to destroy the cancer in a few ways. Firstly, the reactive oxygen species will kill the cancer cells directly. Secondly, they will cause damage to the vasculature that feeds the tumour. Finally, they may hold the potential to cause immunogenic cell death.⁶ 

Immunogenic cell death occurs when cell death is accompanied by immune activation, alerting the immune system to the presence of the cancer and allowing the immune system to attack and destroy it.⁶ Together, by destroying cancerous cells, damaging their blood supply, and potentially activating the immune activation, photodynamic therapy can improve the health of the patient.

Photodynamic therapy studies for prostate cancer

Countless studies that have been completed, are underway and are actively recruiting to study the effects of photodynamic therapy in prostate cancer across the world. Studies focus on using different kinds of photosensitiser molecules, different dosages, different treatment schedules, and different light delivery tactics. They will look at the efficacy of the treatment and the side effects that come along with it.

One study carried out in multiple sites across the US looked at 30 men with prostate cancer and treated them with photodynamic therapy. Their response was then assessed by post-treatment MRI scans and biopsies. They found that the treatment was well tolerated in patients and resulted in a negative biopsy for the majority of the men tested.⁸

Cancer Research UK is currently recruiting patients (up until December 2025) to partake in its clinical trial, studying what dosages of both light and photosensitiser are required to have a therapeutic effect on men with prostate cancer who have not previously had surgery to remove it.³

Advantages and considerations of photodynamic therapy

Photodynamic therapy brings with it many advantages. Due to the direct delivery of light, photodynamic therapy is targeted to the tumour site and generally leaves healthy tissue untouched. This means that the therapy is likely to cause fewer side effects than other therapies including chemotherapy. Photodynamic therapy is also relatively non-invasive which is of huge benefit to cancer patients who may have previously gone through other tough and invasive treatments.⁹ It also doesn’t carry with it the risks that surgery carries such as the risk of anaesthesia or infection.¹⁰

Despite all its benefits, it appears unlikely that photodynamic therapy alone will be sufficient to cause cancer eradication especially if tumours are large. Challenges may also be faced if tumours are in anatomically inaccessible areas. This is because the depth that the light can penetrate is limited, so the photosensitiser molecules will not become activated.⁶ The therapy is also reliant on oxygen availability and tumours are inherently low-oxygen (hypoxic) environments, so this poses another challenge to the therapeutic efficacy of photodynamic therapy.¹⁴ 

Patients receiving this therapy in some cases will need to restrict access to sunlight and artificial light sources following their treatment, but exact details for your safety will be provided by your doctor and care team.¹⁵

Photodynamic therapy in combination with other therapies

Whilst photodynamic therapy alone may not be able to remove entire tumours, when combined with other treatment methods, it becomes more effective. Studies in cell-based models and patients with various cancer types have shown that combining chemotherapy with photodynamic therapy improves patient outcomes and can overcome challenges with cancers that are resistant to different types of chemotherapeutics.^{11, 12} 

Photodynamic therapy has also been studied in combination with surgery and has been shown to reduce recurrence rates of prostate cancers.¹³ Another study examining photodynamic therapy in combination with radiotherapy saw that photodynamic therapy made cells more susceptible to radiotherapy, meaning dosages and regularity of radiotherapy treatments could possibly be reduced.¹⁴

Summary

Photodynamic therapy appears to be a promising, potential new treatment for prostate cancer. With many trials underway to assess its efficacy and side effects, it will take many more years for conclusive results to be gathered and for the potential therapy to be rolled out and widely used in patient groups. However photodynamic therapy may one day be a key player in the treatment landscape for those with prostate cancer and may bring with it many benefits.

For more information regarding ongoing and actively recruiting clinical trials please see: https://clinicaltrials.gov/