Photodynamic therapy is a new selective treatment technique for (vascular) proliferative tissues that was introduced in the late 1970s and has been rapidly developed in recent years. It is a new and rapidly developing therapy completely different from surgery, radiotherapy, chemotherapy and immunotherapy, and has become one of the most active research fields in the world of tumor prevention and treatment science.
Photodynamic therapy is a new disease treatment based on the interaction of light, photosensitizers and oxygen, and the research of photosensitizers is the key to the prospect of photodynamic therapy. Photosensitizers are special chemicals whose basic role is to transfer energy, which can absorb photons and be excited, and quickly transfer the absorbed light energy to another group of molecules, so that they are excited while the photosensitizer itself returns to the ground state.
Photodynamic therapy is the core substance of photodynamic therapy, and the introduction, development and application of PDT are gradually improved with the development of photodynamic therapy.
Indications for photodynamic therapy
1.Pre-cancerous skin diseases and skin malignancies
(1) gaze keratosis
(2) Bowen’s disease
(3) Basal cell carcinoma
(4) Squamous carcinoma.
(5) Kaposi’s sarcoma
(6) Mycosis fungoides
2.PDT for non-malignant skin diseases
(1) Condyloma acuminatum.
(2) Vascular malformation.
(3) Acne vulgaris.
(4) Viral skin disease.
(5) Sebaceous gland hyperplasia.
(6) Photorejuvenation.
Compared with conventional treatments such as surgery, chemotherapy and radiotherapy, photodynamic therapy has the following important advantages.
1.Minimal trauma: With the help of optical fiber, endoscope and other interventional techniques, the laser can be guided deep into the body for treatment, avoiding the trauma and pain caused by open-chest and open-abdomen surgery.
2.Low toxicity: The photosensitive drugs entering the tissue will trigger photodynamic reaction and kill tumor cells only when they reach a certain concentration and are irradiated by sufficient amount of light, which is a local treatment method. The part of human body that is not irradiated by light does not produce such reaction, and the organs and tissues in other parts of human body are not damaged, nor does it affect the hematopoietic function, so the toxic side effects of photodynamic therapy are very low.
3, selective good: photodynamic therapy is the main target of the light irradiation area of the lesion tissue, the normal tissue around the lesion damage is slight, this selective killing effect is difficult to achieve many other treatment means.
4.Good applicability: Photodynamic therapy is effective for different cell types of cancer tissues and has a wide range of applicability; while the sensitivity of different cell types of cancer tissues to radiotherapy and chemotherapy can vary greatly and the application is restricted.
5.Repeatable treatment: Cancer cells are not resistant to photosensitive drugs, and patients will not increase toxic reactions due to multiple photodynamic treatments, so treatment can be repeated.
6.Can be palliative treatment: For patients with advanced tumors, or tumor patients who cannot receive surgery due to advanced age, cardiopulmonary, hepatic and renal insufficiency, or hemophilia, photodynamic therapy is a palliative treatment that can effectively relieve pain, improve quality of life and prolong life.
7.It can improve the efficacy with surgery: for some tumors, surgical resection is performed first, and then photodynamic therapy is applied, which can further destroy the residual cancer cells, reduce the chance of recurrence and improve the completeness of surgery; for some other tumors, it is possible to do photodynamic therapy first to make the tumor shrink before resection, which can expand the indications for surgery and improve the success rate of surgery.
8.It can eliminate the hidden cancer lesions: clinically, some tumors, such as bladder metastatic cell carcinoma, may have scattered tiny cancer nests invisible to the naked eye outside the main lesion, conventional treatment can only remove the main lesion and can do nothing about the hidden cancer nests, but using photodynamic therapy to adopt the method of surface irradiation after filling the whole bladder to eliminate all the tiny lesions that may exist, thus greatly reducing the chance of tumor recurrence.
9.Protecting appearance and important organ functions: For skin cancer of face, oral cancer, penile cancer, cervical cancer, retinoblastoma, etc., the application of photodynamic therapy may effectively kill cancer tissues and minimize the damage to the epithelial structure and collagen scaffold of the developing organ, so that the appearance will be less affected and the organ shape and normal physiological functions will be kept intact after the wound healing.
The results of clinical trials show that ALA-photodynamic therapy for urethral warts has a 95% wart clearance rate and is well tolerated by patients; for urethral warts, the wart clearance rate is 98.42%. The recurrence rate is only 10.77%. At the same time, the safety is high: no scarring, and the incidence of adverse reactions is only 7.67%.