ISSN 2398-2969      

Photodynamic therapy


Synonym(s): PDT


  • Photodynamic therapy (PDT) describes a method of cancer therapy Cancer therapy overview using interactions of a photosensitizing agent, light and oxygen.
  • PDT is a promising method of treating superficial carcinomas Cutaneous neoplasia that is non-invasive, provides good cosmesis and carries minimal risk of toxicity.


  • Treatment of superficial carcinomas Cutaneous neoplasia, where surgery is not feasible or may not provide a good cosmetic outcome.


  • Certain agents, eg porphyrins and their derivatives are preferentially distributed into malignant tissues rather than normal tissues.
  • These agents can be "excited" by light of appropriate wavelength causing reactive oxygen species (ROS) stress and producing cytotoxic free radicals, which kill the cell and stimulate a local inflammatory response.

History and background

  • PDT was first investigated in the 1970's when it was found that porphyrins were preferentially distributed into malignant tissues rather than normal tissues.
  • The technique was slow to gain acceptance because the "first generation" photodynamic agents were slow to clear from normal cells with the result that treated human patients had to remain out of bright light, eg sunlight, for several weeks to avoid severe skin reactions. The potential for the technique was demonstrated, however, on laboratory animals and on some human patients with locally advanced carcinomas of the head and neck, bladder, esophagus and bronchus.
  • The availability of hematoporphyrin derivatives with faster tissue clearance times stimulated more interest in PDT and a number of human and veterinary clinical trials with encouraging results were published.
  • PDT has become established as a safe, minimally invasive and effective method of treatment for certain human cancers and is offered at several major cancer centers in the UK and Europe.
  • It is used in the treatment of head and neck cancers because of its excellent cosmetic results. PDT can also be used in any hollow organ accessible to a fiber optic for light delivery, thus it is often used in human prostate, bladder and esophageal cancer.

Veterinary clinical results

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Conclusion and future directions

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Further Reading


Refereed Papers

  • Recent references from PubMed and VetMedResource.
  • Oakley E, Bellnier D, Hutson A et al (2020) Irradiance, Photofrin® dose and initial tumor volume are key predictors of response to interstitial photodynamic therapy of locally advanced cancers in translational models. Photochem Photobiol 96 (2), 397-404 PubMed.
  • Muhanna N, Chan H, Townson J L et al (2020) Photodynamic therapy enables tumor specific ablation in preclinical models of thyroid cancer. Endo Relat Cancer 27 (2), 51-53 PubMed.
  • Shakhova M, Loginova D, Meller A et al (2018) Photodynamic therapy with chlorin-based photosensitizer at 405 nm: numerical, morphological, and clinical study. J Biomed Opt 23 (9), 1-9 PubMed.
  • Harris K, Oakley E, Bellnier D et al (2017) Endobronchial ultrasound-guidance for interstitial photodynamic therapy of locally advanced lung cancer - a new interventional concept. J Thoracic Dis 9 (8), 2613-2618 PubMed.
  • Gao H, Shi L, Yin H et al (2016) Evaluation of the effect of photodynamic therapy with hematoporphyrin monomethyl ether on VX2 tumors implanted in the rectal submucosa of rabbits. J Photochem Photobiol B 163,162-9 PubMed.
  • Zhang Y, He L, Wu J et al (2016) Switchable PDT for reducing skin photosensitization by a NIR dye inducing self-assembled and photo-disassembled nanoparticles. Biomaterials 107, 23-32 PubMed.
  • Bexfield N H, Stell A J, Gear R N et al (2008) Photodynamic therapy of superficial nasal planum squamous cell carcinomas in cats: 55 cases. J Vet Intern Med 22 (6), 1385-9 PubMed.

Other sources of information

  • Varga M (2014) Neoplasia. In: Manual of Rabbit Medicine. Eds: Meredith A & Lord B. BSAVA, UK. pp 264-273.

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