Photodynamic therapy?

[chrisho]

Hi, everybody

Is there anyone aware of the recent progress in photodynamic therapy?

It is documented in Perez. I think it is already used in other fields such as Ophthalmology, Dermatology, and Surgical Oncology, etc.

The principle behind the treatment is quite similar to the current radiotherapy, i.e. combining photon (laser) plus photosensitizers...

Its limitation is by the penetration depth inheritable to visible light (around 5 mm), so it can only be used for superficial tumors or neovasculizations.

If well established, I think it can be used for a lot of disease entities, e.g. age-related macular degeneration, skin cancer, Barret esophagus, etc.

It will be possibly better and even more commercially available than proton therapy or brachytherapy concerning the cost-effectiveness issue...
(Not like IMRT, it will not be severely cut down because it is cheaper )

Thinking about UV light, it is also used by many dermatologist to treat a lot of skin disorders, like psoriasis, atopic dermatitis, CTCL, etc.

By definition, a radiation oncologist is eligible to use ionizing radiation in the treatment of numerous benign and malignant conditions.

I wonder whether it is being researched or developed by anyone in the field. Does anyone have an opinion on the future use of this technique?

Thanks!!

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[IndyXRT]

I just heard a talk by Dr. Glatstein about PDT. It was certainly intriguing, although I think it's a ways from being ready for prime time. Certainly something to watch.

 

[Palex80]

I've seen it being used in bronchial mucosa lesions after radiation therapy, when concerns were raised about late toxicity. The results were not bad.

 

[TupacalipseT96]

PDT has been around since the 80's, it is nothing particularly new. Its success has been limited, however, due to unwanted peripheral toxicity and photosensitization (often patients cannot have direct contact with light for many months) following systemic administration. Thus, recent efforts, including my own research, have aimed to localize the photosensitizing agents specifically to tumors or tumor vasculature. [Thus you would have two means of damage control: 1.) by where you shine the light, 2.) by where the phototoxin localizes]

In addition to targetting neovasculature, my project attached a SV40 nuclear localization sequence to increase toxin proximity to the DNA (since free radical toxicity is distance dependent as you mentioned). Obviously, I think intracellular localization of the photosensitizer will be very big in enhancing the toxicity-to-dose ratio. It would also reduce auxiliary damage due to stray free radicals destroying neighboring cell membrane.

Also, PDT uses non-ionizing radiation (toxicity comes from the phototoxin, not the radiation itself) -- so technically Rad Oncs wouldn't be much more qualified to use it than surgeons, though I imagine they may be interested in its application once refined.

It is still a hot topic for research, and I believe once a robust targetting mechanism is established, PDT will have much promise. However, like many proposed alternative cancer treatment modalities, the issue of specificity remains the major problem.