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PHOTODYNAMIC THERAPY (PDT) - Coggle Diagram
PHOTODYNAMIC THERAPY
(PDT)
Principles
Essential Components
Photosensitizer (PS)
An ideal PS agent should be a single pure compound
Have a high absorption peak between 600 and 800 nanometers (nm) (red to deep red)
To allow quality control analysis with low manufacturing costs and good stability in storage.
Light Source
Red and infrared radiations penetrate more deeply. The region between 600 and 1200 nm is often called the optical window of tissue.
Light up to only approximately 800 nm can generate 1O2
Oxygen
administration route
about 3 hours later
irradiation with light at a specific wavelength
approximately 24 to 72 hours post light treatment
high number of 1O2 leads to direct tumor cell death, damage to the microvasculature
which triggers the induction of a local inflammatory reaction
which removes dead cells, restore normal cell homeostasis and develop immunity
Irradiation activates the PS and in the presence of molecular oxygen
triggers a photochemical reaction
culminates and produces singlet oxygen (1O2)
depending on the substance in PS, it will accumulate in target cells (ie : cancer cells)
systematically - IV
locally - topical cream
Advantages
It has no long-term side effects when used properly
Less invasive than surgery
Can be targeted very precisely
Takes short time & can be done as an outpatient procedure
Little or no scarring after the site heals.
Costs less than other cancer treatments
Can be repeated many times at the same site if needed
Disadvantages
Unable to use on patients who have certain blood disease
Cannot be used to treat cancers that have spread to many regions in body
Drugs used can leave patient very sensitive to light for some time, so special precautions must be taken after the drugs administration
Stay indoor for certain period
Stay out of strong and direct light
Wear protective clothing and wide-brimmed hats to avoid sunlight when outdoors.
Avoid applying powders, make-up or harsh cleansing soaps to skin until skin is fully healed
Can only treat regions where light can reach
It can be used to treat problems on or just under the skin, or in the lining of organs where light can be reached
Cannot treat large cancers or cancers that grow in deep surface as light cannot reach the region
Why PDT?
Provide excellent cosmetic outcomes for skin cancer patient
no significant changes in tissue temperature and the preservation of connective tissue which may lead to fibrosis and cause tissue scarring.
Used for inoperable tumours
can achieve improvement in patient quality of life when other treatment option is not useful
Can used either before or after chemotherapy, radiotherapy or surgery
PDT will not compromise other therapeutic modalities since radio-resistance or chemo-resistance will not affect the sensitivity of PDT.
Performed in an outpatient or ambulatory setting
Cheap but also making the treatment patient-friendly.
Harmless/painless procedure
A procedure which kills cancer cell without causing any side effects
Drugs
Porfimer sodium (Photofrin)
Activated by red light from a laser
Can treat patients with certain cancers like esophagus and lung cancer
Aminolevulinic acid (ALA or Levulan)
A special blue light is used to activate this drug
Used to treat actinic keratosis (AK), a skin condition that can become cancer, and is used only on the face or scalp