It is considered by specialists that photodynamic therapy (PDT), as a scientific, appropriate, noninvasive or micro-invasive therapy which developed at the beginning of the 21st century, will open the new epoch in tumor therapy in future, just as penicillin invented in 1930s made death rate of infectious diseases such as pneumonia decrease dramatically.
PRINCIPLE
PDT is a non-thermal light chemical reaction and need oxygen, photosensitive substance (photo-sensitizer) and laser simultaneously to participate in. Photo-sensitizer is absorbed by neoplasm tissue and
accumulates in the cells for a long time. Photo-sensitizer is activated with the appropriate wavelength of light and reacts with oxygen to generate reactive single state oxygen and hotochemical substance that are toxic to cells leads to apoptosis and necrosis of cancer; PDT can result in local vascular lesion of tumor; PDT can make tumor tissue ischemic necrosis and initiate immune reaction of antitumor. Photo-sensitizer is exposed to laser light and subsequently reacts with oxygen, and gives rise to single state oxygen and toxic photochemical substance.
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PROCEDURE
- Photosensitizer (Photofrin, porfimer sodium), 2mg/kg,is administrated intravenously 48 hours before scheduled light activation.
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- Laser light irritation: 48 hours after photosensitizer administration, 630-nm red laser light is delivered through optic cables (thin fibers that transmit light) to deliver light to areas inside the body. The light used for PDT can come from a laser or other sources of light. The total light dose administered ranges from 20 to 30 J/cm2.The light irritation is often repeated 72 hours after photo-sensitizer administration.
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- The delivery of laser fiber may be through endoscopes, such as gastrointestinal endoscope(for esophageal or gastric cancer) or bronchendoscope (for lung cancer) , or intraoperatively.
- PDT may also be repeated and may be used with other therapies, such as surgery, radiation, or chemotherapy.
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INDICATION
Formally Approved
America
- Esophageal cancer (partically or completely obstructive)
- Redical treatment of early stage esophageal cancer
- Microinvasive non-small cell lung cancer, unable to be given surgery and radiotherapy
- Obstructingnon-small cell lung cancer
Europe
- Esophageal cancer and lung cancer
- Radical treatment of early stage lung cancer
Japan
- Early stage oflung cancer
- Superficial esophageal cancer
- Superficial gastric cancer
- Early cervical cancer and metaplastic proliferation
Canada
- Obstructing esophageal cancer, unable to begiven Nd:YAG laser therapy
- Early non-small cell lung cancer
Good effects showed by study
Barrett’s esophagus with high-degree displasia and esophageal adenocarcinoma
Effective report from clinics
Early stage of carcinoma of oral cavity, tumor of head-neck, brain tumor, pleural or peritoneal mesothelioma, sarcoma in abdominal cavity, eye tumor, asophary geal cancer, tumor of chest wall, breast cancer, gynecologic cancer, rectal cancer, Kaposi sarcoma, skin cancer
Good prospects of application
Bone marrow, rheumatoid arthrositis, arteriolosclerosis, prevention of restricture after vascular plasticity, macula degeneration, streptococcus infection in peridentium, helicobacter pylori, wound infection.
Advantages
- Relative selectivity and tissue speciality for tumor cells;
- Low toxicity, good safety, no immunosuppression and marrow inhibition;
- No bad effect on other therapies, complementary to surgery, radiotherapy and chemotherapy;
- Short treatment time;
- initiating therapeutic effectwithin 48-72 hours;
CLINICAL APPLICATION
Oral- pharygeal tumor
Early oral, nosal and nasopharygeal cancer: PDT had effective rates of 75%-100%.
Esophageal cancer
- PDT had radical effect for early esophageal cancer;
- PDT brings the five-year survival rate of 74%-84% in T1 and T2 stage of esophageal squamous and adenocarcinoma; PDT can effectively ameliorate obstruction of advanced esophageal carcinoma. Very effective for cervical esophageal cancer, Able to treat undermucosal disseminated and latent cancer. For cancer which grows into intracavity and stent has been placed, PDT can eradicate neoplasm in cavity.
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Barrett esophagus
Normal squamous epithelium lining the esophagus is replaced by glandular columanar epithelium, that called Barrett esophagus, which increases the risk of esophageal adenocarcinoma. PDT not only can effectively eradicate Barrett epithelium, but has good result for early adenocarcinoma. |
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Lung cancer
- For lung cancer with bronchial obtruction, PDT induce improvement of air-way obstruction
- Treatment of lung cancer with PDT was approved by FDA,USA
- For early bronchial cancer, PDT has the cure rate of 90%;for obstructive cancer, the improvement rate of 85 percent.
Gastric cancer
- PDT can eradicate cancer for 80 % ofearly gastric cancer
- PDT can improve symptoms of advanced gastric cancer
Colon-rectal carcinoma
- PDT is especially indicated to colon-rectal adenocarcinoma and small cancer
- PDT can improve symptoms, such as tenesmus, pain and bleeding,of 55 percent of patients with unresectable colon-rectal carcinoma
Cholangiocarcinoma
PDT can effectively eliminate obstruction of bile duct in patients with cholangiocarcinoma in hepatic hilum, treatment of which is very difficult with traditional methods.
Pancreatic carcinoma and cancer ofVater’s ampulla
PDT, which is performed with inserting light-guiding fiber through endoscopy or percutaneously, can control development of pancreatic carcinoma and Vater’s ampulla cancer.
Tumor in abdominal cavity
It was reported that PDT can effectively treat the postoperative recurrent cancer of rectum in pelvic cavity, recurrent colonic carcinoma with local metastasis and sarcoma in abdominal cavity.
Bronchial carcinoma (lung cancer)
In patients with stage 1 of bronchial carcinoma,5-year survival ratebrought by PDT was ashigh as 93 percent.
In advanced bronchial carcinoma, 55% of tumor mass shrinkaged, 49% ofimproved after PDT.
Bronchial bleeding
PDT can induce stopping of hemoptysis induced by various causes. |
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Pleural and peritoneal mesothelioma
- Intraoperative application of PDT can eliminate tumor especially for patients with tumor which can’t be totally resected.
- The 2-year survival rate of 23 % was seen in 37 patients withmesothelioma, and the median survival was 61 months in patients with 1 and 2 stage of disease.
Brain tumor
PDT has a special effect to brain tumor, especially to glioma, because cells of brain tumor have high capacity to concentrate photosensitizer.
Tumors of genitourinary tract
Bladder cancer in situ can be eradicated by PDT. Seventy-one percent of advanced cases had got improvement after PDT.
Skin and subcutaneous tumor
PDT can effectively treat various cancer and metastatic cancer of skin and subcutaneous tissues.
Gynecologic tumor
PDT is effective for treatment of vaginocarcinoma, cervical cancer in situ, and metastatic vaginocarcinoma.
LIMITATION OF PDT
The light needed to activate most photosensitizers cannot pass through more than about one-third of an inch of tissue (1 centimeter). For this reason, PDT is usually used to treat tumors on or just under the skin or on the lining of internal organs or cavities . PDT is also less effective in treating large tumors, because the light cannot pass far into these tumors. PDT is a local treatment and generally cannot be used to treat cancer that has spread cancer.
ADVERSE EFFECTS
Does PDT have any complications or side effects?
Porfimer sodium makes the skin and eyes sensitive to light for approximately 4 weeks after treatment. Thus, patients are advised to avoid direct sunlight and bright indoor light for at least 4 weeks.
Photo-sensitizers tend to build up in tumors and the activating light is focused on the tumor. As a result, damage to healthy tissue is minimal. However, PDT can cause burns, swelling, pain, and scarring in nearby healthy tissue. Other side effects of PDT are related to the area that is treated. They can include coughing, trouble swallowing, stomach pain, painful breathing, or shortness of breath; these side effects are usually temporary.
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