Photodynamic Therapy (PDT)
Photodynamic therapy, PDT for short, is an innovative and promising, minimally invasive therapy method in biological cancer treatment.
In this therapy, a substance known as a photosensitizer is concentrated in the tumour tissue and then irradiated with light of a certain wavelength. The coincidence of light and photosensitizer leads to the formation of certain oxygen radicals which kill the diseased cells. In contrast to diseased cells, healthy cells remain largely unaffected by this photochemical reaction.
Furthermore, PDT triggers an actively specific immune phenomenon, since the treatment increases the release of tumour antigens, thereby promoting the specific immune performance of the tumour carrier.
Mode of action
The basic principle of the photodynamic effect is based on the tumour-selective concentration of light-sensitive substances. These photosensitizers have the ability to absorb the energy of light and pass it on to oxygen molecules. This produces the so-called singlet oxygen, an energetically excited form of molecular oxygen. These oxygen radicals are capable of destroying cell structures that are vital for the tumour through photooxidation.
In addition to cellular damage, tumour vascularisation, i.e. the formation of new blood vessels, collapses just a few minutes after exposure to light. The interaction of both effects is able to destroy the tumour. The only known side effect of this treatment is the skin's sensitivity to light, so that PDT represents a very low risk for the affected patient.
How effective PDT is depends not only on the phototherapeutic potential of the sensitizer but also on the quality of the light application systems. Lamp systems and diode lasers have proven to be powerful light sources in the red spectral range. Fibre-optic light applicators are designed according to the geometry of the organ to be irradiated. For tubular organs, for example in the bronchial and gastrointestinal area, cylindrical emitters are used. Spherical hollow organs, such as the urinary bladder, can be illuminated by spherical emitters.
Areas of application
Photodynamic therapy is currently used in various fields for palliative and curative tumour therapy.
According to the largest published study to date on PDT in Barrett's carcinoma or high grade dysplasia (HGD), complete treatment success was demonstrated in over 80 percent of 100 patients treated. The use of PDT in early-stage gastric cancer also appears promising.
In a randomized study, patients received adjuvant PDT after transurethral resection of bladder tumours. It was found that the average time to relapse after PDT was significantly longer than in the non-adjuvant control group. However, the use of this procedure is also being scientifically researched in prostate and bladder cancer (interstitial laser therapy), and ongoing studies show positive results.
On the one hand, PDT treatment appears to induce necrosis, i.e. the tumour tissue dies. On the other hand, healthy tissue is spared and organ function is preserved. PDT considerably reduces the risk of damage to the surrounding nerves, muscles, urethral sphincter, bladder and rectum.
Several clinical studies have shown the efficacy of PDT in early-stage cancers of the oral cavity, pharynx and larynx. PDT also has high potential as an adjuvant therapy after surgical treatment of extensive primary tumours.
In dermatology, PDT's mode of action as described above results in a broad spectrum of applications, both with regard to effective cell destruction in oncology and with regard to the induction of immuno-modulatory effects in inflammatory dermatoses.
Initial trials have also shown promising results in Hodgkin's lymphoma. Already after 2-3 sessions a drastic reduction of the affected lymph nodes can be observed.
Clinical trials have also shown PDT to be effective in osteosarcomas (bone tumours) and their lung metastases.
Brief excursion: Intravascular laser blood irradiation
The healing effect of light is also used in intravascular laser blood irradiation. This form of therapy was first carried out about 25 years ago in the former Soviet Union. In the meantime, it has also achieved a high degree of popularity in the West and extensive international studies have shown very good therapeutic successes. Using a special disposable light probe, laser light is conducted directly via the vein into the blood, whereby an exact dosage of the laser intensity is required in order to use the entire effective spectrum of the laser light on the one hand, but on the other hand to avoid a warming effect in the vein.
The positive effects of laser blood irradiation are extremely diverse. It improves blood circulation, especially microcirculation, reduces inflammatory activity in the body, strengthens the immune system and stimulates blood formation. The overall result is an improved blood composition and an improved supply of oxygen and important nutrients to the cells. This results in an optimised function of the organs and tissue, a relief of pain and an increase in performance. This in turn goes hand in hand with a strengthening of the body's self-healing capacities, which enables the body to deal better with chronic diseases.
The intravascular laser blood treatment is therefore particularly well suited to alleviating the symptoms of fatigue associated with cancer.
Lyme disease therapy with laser blood irradiation
Photodynamic therapy (PDT) is not only a promising treatment approach in the context of holistic cancer treatment, especially for prostate and bladder cancer, it also achieves excellent results in the treatment of antibiotic-resistant infectious diseases such as MRSA and Lyme disease.
Laser blood irradiation is a minimally invasive therapy option. In this procedure, a laser light is guided directly into the flowing blood via a venous catheter and thus causes positive changes in the immune system. Almost all patients show a general stabilization and increase in energy.
Photodynamic laser therapy - laser blood irradiation for Lyme disease - is a direct evolution of photodynamic laser therapy as it was previously used as antibacterial photodynamic therapy (PDT) mainly in dentistry and for the destruction of bacteria.
In contrast to photodynamic laser therapy, laser blood irradiation does not introduce a light-sensitive substance (photosensitizer based on plant substances) into the bloodstream. Instead, the laser light is fed directly into the flowing blood to cause photochemical reactions.
In Lyme disease treatment, additional intake of curcumin or hypercin can increase the sensitivity of parasites, bacteria and viruses to light so that they are destroyed or die off.