Photodynamic therapy of oral cancer. A review of basic mechanisms and clinical applications

Epidemiology, Diagnostics, and Therapy of Oral Cancer-Update Review

Oral cavity and lip cancers are the 16th most common cancer in the world. It is widely known that a lack of public knowledge about precancerous lesions, oral cancer symptoms, and risk factors leads to diagnostic delay and therefore a lower survival rate. Risk factors, which include drinking alcohol, smoking, HPV infection, a pro-inflammatory factor-rich diet, and poor oral hygiene, must be known and avoided by the general population. Regular clinical oral examinations should be enriched in an oral cancer search protocol for the most common symptoms, which are summarized in this review. Moreover, new diagnostic methods, some of which are already available (vital tissue staining, optical imaging, oral cytology, salivary biomarkers, artificial intelligence, colposcopy, and spectroscopy), and newly researched techniques increase the likelihood of stopping the pathological process at a precancerous stage. Well-established oral cancer treatments (surgery, radiotherapy, chemotherapy, and immunotherapy) are continuously being developed using novel technologies, increasing their success rate. Additionally, new techniques are being researched. This review presents a novel glance at oral cancer-its current classification and epidemiology-and will provide new insights into the development of new diagnostic methods and therapies.

Effectiveness of photodynamic therapy (PDT) in the management of symptomatic oral lichen planus -A systematic review

Background

Oral Lichen Planus (OLP) is a chronic mucocutaneous inflammatory disease of unknown aetiology characterized by T cell mediated autoimmune response which trigger apoptosis of basal cells of an oral epithelium. Corticosteroids are the primary therapeutic option for symptomatic OLP however treatment of lesions unresponsive to corticosteroids that tend to recur are becoming challenging for the clinicians. Currently photodynamic therapy (PDT) is being explored as a new curative option for reduction of pain and/or burning sensation associated with OLP lesions.

Aims and objective

The aim of this systematic review was to analyse studies from literature on the therapeutic effectiveness of PDT in management of symptomatic OLP unresponsive to corticosteroid therapy.

Methods

The electronic retrieval systems and databases PUBMED [MEDLINE], EMBASE, SCOPUS, WEB OF SCIENCE, GOOGLE SCHOLAR, and SCIENCE DIRECT were searched independently by two authors for relevant articles from January 2015 till July 2021. Primary studies focussed on the role of PDT in treatment of symptomatic OLP and published in English were included.

Results

Out of the 370 articles, only ten studies met the selection criteria. Included studies demonstrated PDT as an effective alternative modality to treat symptomatic OLP with no drop outs. In all studies, with PDT reduction in lesion size and VAS score was observed during each follow up sessions and after treatment (approx. 12 weeks) when compared to pre-treatment level (p < 0.001). Four studies noted PDT to be more effective than topical corticosteroids in reduction of signs and symptoms of OLP (p = 0.001).

Conclusion

In the future, long-term studies on larger population should be conducted to establish the clinical effectiveness in PDT in symptomatic OLP. Studies should take into consideration different sources of light and photosensitizers to determine the ideal parameters of PDT treatment for OLP. Wavelength is the most important factor in all types of photo therapies, so the most appropriate wavelength should be selected to obtain better outcome.

Photodynamic therapy in oral cancer: a review of clinical studies

A significant mortality rate is associated with oral cancer, particularly in cases of late-stage diagnosis. Since the last decades, oral cancer survival rates have only gradually improved despite advances in treatment. This poor success rate is mainly due to the development of secondary tumors, local recurrence, and regional failure. Invasive treatments frequently have a negative impact on the aesthetic and functional outcomes of survivors. Novel approaches are thus needed to manage this deadly disease in light of these statistics. In photodynamic therapy (PDT), a light-sensitive medication called a photosensitizer is given first, followed by exposure to light of the proper wavelength that matches the absorbance band of the photosensitizer. The tissue oxygen-induced cytotoxic free radicals kill tumor cells directly, harm the microvascular structure, and cause inflammatory reactions at the targeted sites. In the case of early lesions, PDT can be used as a stand-alone therapy, and in the case of advanced lesions, it can be used as adjuvant therapy. The current review article discussed the uses of PDT in oral cancer therapy based on recent advances in this field.

Nanophotosensitizers Composed of Phenyl Boronic Acid Pinacol Ester-Conjugated Chitosan Oligosaccharide via Thioketal Linker for Reactive Oxygen Species-Sensitive Delivery of Chlorin e6 against Oral Cancer Cells

Chlorin E6 (Ce6)-incorporated nanophotosensitizers were fabricated for application in photodynamic therapy (PDT) of oral cancer cells. For this purpose, chitosan oligosaccharide (COS) was conjugated with hydrophobic and reactive oxygen species (ROS)-sensitive moieties, such as phenyl boronic acid pinacol ester (PBAP) via a thioketal linker (COSthPBAP). ThdCOOH was conjugated with PBAP to produce ThdCOOH-PBAP conjugates and then attached to amine groups of COS to produce a COSthPBAP copolymer. Ce6-incorporated nanophotosensitizers using the COSthPBAP copolymer were fabricated through the nanoprecipitation and dialysis methods. The Ce6-incorporated COSthPBAP nanophotosensitizers had a small diameter of less than 200 nm with a mono-modal distribution pattern. However, it became a multimodal and/or irregular distribution pattern when H₂O₂ was added. In a morphological observation using TEM, the nanophotosensitizers were disintegrated by the addition of H₂O₂, indicating that the COSthPBAP nanophotosensitizers had ROS sensitivity. In addition, the Ce6 release rate from the COSthPBAP nanophotosensitizers accelerated in the presence of H₂O₂. The SO generation was also higher in the nanophotosensitizers than in the free Ce6. Furthermore, the COSthPBAP nanophotosensitizers showed a higher intracellular Ce6 uptake ratio and ROS generation in all types of oral cancer cells. They efficiently inhibited the viability of oral cancer cells under light irradiation, but they did not significantly affect the viability of either normal cells or cancer cells in the absence of light irradiation. The COSthPBAP nanophotosensitizers showed a tumor-specific delivery capacity and fluorescence imaging of KB tumors in an in vivo animal tumor imaging study. We suggest that COSthPBAP nanophotosensitizers are promising candidates for the imaging and treatment of oral cancers.

Recent Advances in Photodynamic Imaging and Therapy in Hepatobiliary Malignancies: Clinical and Experimental Aspects

The therapeutic and diagnostic modalities of light are well known, and derivative photodynamic reactions with photosensitizers (PSs), specific wavelengths of light exposure and the existence of tissue oxygen have been developed since the 20th century. Photodynamic therapy (PDT) is an effective local treatment for cancer-specific laser ablation in malignancies of some organs, including the bile duct. Although curability for extrahepatic cholangiocarcinoma is expected with surgery alone, patients with unresectable or remnant biliary cancer need other effective palliative therapies, including PDT. The effectiveness of PDT for cholangiocarcinoma has been reported experimentally or clinically, but it is not the standard option now due to problems with accompanied photosensitivity, limited access routes of irradiation, tumor hypoxia, etc. Novel derivative treatments such as photoimmunotherapy have not been applied in the field hepatobiliary system. Photodynamic diagnosis (PDD) has been more widely applied in the clinical diagnoses of liver malignancies or liver vascularization. At present, 5-aminolevulinic acid (ALA) and indocyanine green (ICG) dyes are mainly used as PSs in PDD, and ICG has been applied for detecting liver malignancies or vascularization. However, no ideal tools for combining both PDD and PDT for solid tumors, including hepatobiliary malignancies, have been clinically developed. To proceed with experimental and clinical trials, it is necessary to clarify the effective photosensitive drugs that are feasible for photochemical diagnosis and local treatment.

Reactive oxygen species-sensitive nanophotosensitizers of aminophenyl boronic acid pinacol ester conjugated chitosan-g-methoxy poly(ethylene glycol) copolymer for photodynamic treatment of cancer

The aim of this study is to prepare reactive oxygen species (ROS)-sensitive nanophotosensitizers for targeted delivery of chlorin e6 (Ce6) and photodynamic tumor therapy. For this purpose, thiodipropionic acid (TDPA) was conjugated with phenyl boronic acid pinacol ester (PBAP) (TDPA-PBAP conjugates) and then the TDPA-PBAP conjugates were attached to the chitosan backbone of chitosan-g-methoxy poly(ethylene glycol) (ChitoPEG) copolymer (ChitoPEG-PBAP). Ce6-incorporated ChitoPEG-PBAP nanophotosensitizers have an ROS-sensitive manner in vitro. The size of ChitoPEG-PBAP nanoparticles increased or disintegrated in a responsive manner against H₂O₂ concentration. The Ce6 release rate from ChitoPEG-PBAP nanophotosensitizers also increased by adding H₂O₂. These results indicated that nanophotosensitizers have sensitivity against ROS and showed triggered Ce6 release behavior. ChitoPEG-PBAP nanophotosensitizers can be more efficiently internalized into cancer cells compared to Ce6 alone and then produce ROS in a more efficient manner. Furthermore, ChitoPEG-PBAP nanophotosensitizers suppressed the viability of cancer cells in vitro and tumor growth in vivo with higher efficacy compared to Ce6 alone. Furthermore, ChitoPEG-PBAP nanophotosensitizers were efficiently delivered to irradiated tumor tissues, indicating that ChitoPEG-PBAP nanophotosensitizers can be delivered to the tumor with ROS-sensitive manner. We suggest that a ChitoPEG-PBAP nanophotosensitizer is a promising candidate for photodynamic therapy of cancers.

Nanophotosensitizers for Folate Receptor-Targeted and Redox-Sensitive Delivery of Chlorin E6 against Cancer Cells

In this study, FA-PEG₃₅₀₀-ss-Ce6tri copolymer was synthesized to deliver photosensitizers via redox-sensitive and folate receptor-specific manner. Folic acid (FA) was attached to amine end of poly (ethylene glycol) (PEG₃₅₀₀) (FA-PEG₃₅₀₀ conjugates) and cystamine-conjugated chlorin e6 (Ce6) (Ce6-cystamine conjugates). FA-PEG₃₅₀₀ was further conjugated with Ce6-cystamine to produce FA-PEG₃₅₀₀-ss-Ce6 conjugates. To the remaining amine end group of Ce6-cystamine conjugates, Ce6 was attached to produce FA-PEG₃₅₀₀-ss-Ce6tri. Nanophotosensitizers of FA-PEG₃₅₀₀-ss-Ce6tri copolymer were smaller than 200 nm. Their shapes were disintegrated by treatment with GSH and then Ce6 released by GSH-dependent manner. Compared to Ce6 alone, FA-PEG₃₅₀₀-ss-Ce6tri copolymer nanophotosensitizers recorded higher Ce6 uptake ratio, reactive oxygen species (ROS) production and cellular cytotoxicity against KB and YD-38 cells. The in vitro and in vivo study approved that delivery of nanophotosensitizers is achieved by folate receptor-sensitive manner. These results indicated that FA-PEG₃₅₀₀-ss-Ce6tri copolymer nanophotosensitizers are superior candidate for treatment of oral cancer.

Raman microspectroscopy of Hematoporphyrins. Imaging of the noncancerous and the cancerous human breast tissues with photosensitizers

Raman microspectroscopy combined with fluorescence were used to study the distribution of Hematoporphyrin (Hp) in noncancerous and cancerous breast tissues. The results demonstrate the ability of Raman spectroscopy to distinguish between noncancerous and cancerous human breast tissue and to identify differences in the distribution and photodegradation of Hematoporphyrin, which is a photosensitizer in photodynamic therapy (PDT), photodynamic diagnosis (PDD) and photoimmunotherapy (PIT) of cancer. Presented results show that Hematoporphyrin level in the noncancerous breast tissue is lower compared to the cancerous one. We have proved also that the Raman intensity of lipids and proteins doesn't change dramatically after laser light irradiation, which indicates that the PDT treatment destroys preferably cancer cells, in which the photosensitizer is accumulated. The specific subcellular localization of photosensitizer for breast tissues samples soaked with Hematoporphyrin was not observed.

Effective treatment of 7,12-dimethylbenz(a)anthracene-induced hamster buccal pouch precancerous lesions by topical photosan-mediated photodynamic therapy

BACKGROUND

Previous studies found that topical photodynamic therapy (PDT) is very effective for human oral precancerous lesions.

METHODS

This study evaluated whether topical photosan-mediated PDT (topical photosan-PDT), using a 640-nm light-emitting diode (LED) light, is an effective treatment modality for hamster buccal pouch precancerous lesions. Fourteen 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch precancerous lesions were treated with topical photosan-PDT using the 640-nm LED light twice a week.

RESULTS

All 14 of the precancerous lesions showed a complete histologically confirmed response to the lesions after an average of 3.79 (range, 3-5) PDT treatments. Normal and precancerous pouch mucosae in the other 4 hamsters received 17 or 19 treatments of topical photosan-PDT showed no cumulative side effects. No recurrence of the lesions was found in these 18 PDT-treated hamsters after a follow-up period of 50 weeks.

CONCLUSION

Our findings indicate that topical photosan-PDT is a very effective treatment modality for DMBA-induced hamster buccal pouch precancerous lesions.

A review of risk factors and genetic alterations in head and neck carcinogenesis and implications for current and future approaches to treatment

Head and neck cancer is the fifth most common cancer worldwide but the most common malignant disease site in central Asia. The treatment of head and neck cancer is one of the most challenging in clinical oncology because of the high content of hypoxic cells of the cancer which increases resistance to therapy and also because of the high capacity of the cancer to regrow during treatment. For unresectable tumours, radiotherapy and chemotherapy alone or more often in combination is the treatment of choice. The aim of this paper is to review current understanding of carcinogenesis of head and neck cancer in relation to predisposing risk factors in general and for specific sub-sites and how these risk factors interact with the main reported genetic alterations in the progression of the cancer. The implications of these changes in determining choice of therapy are also discussed from a brief historical perspective of the various treatment approaches of head and neck cancer.

The status of in vivo autofluorescence spectroscopy and imaging for oral oncology

Autofluorescence spectroscopy and imaging have been studied for the early detection and classification of (pre)malignancies of the oral mucosa. In the present review we will give an overview of the literature on autofluorescence imaging and spectroscopy for various clinical questions. From the studies performed so far we hope to conclude whether autofluorescence spectroscopy and imaging are helpful in the diagnosis of lesions of the oral mucosa, and if this is the case: for which clinical questions they are suitable. A strong emphasis is put on in vivo human studies of the oral mucosa.

Photodynamic Therapy of oral dysplasia with topical 5-aminolevulinic acid and light-emitting diode array

BACKGROUND AND OBJECTIVES

In Taiwan, more than two million people have the betel quid (BQ) chewing habit which is a risk factor related to premalignant lesion and squamous cell carcinoma of oral cavity. We developed a light-emitting diode (LED) array combined with topical 5-aminolevulinic acid (ALA) for photodynamic therapy (PDT) and evaluated its effectiveness for the treatment of oral lesions.

STUDY DESIGN/MATERIALS AND METHODS

We compared the ALA-PDT effect of the homemade LED array to that of a commercial light source on cultured Ca9-22 human gingival carcinoma cells and the DMBA-induced hamster buccal pouch carcinoma model. Furthermore, we treated several patients having an oral lesion using a topical ALA delivery system and the LED array.

RESULTS

The LED array light source was as effective as the commercial light source for ALA-PDT in cultured Ca9-22 cells with LD(50) of 4.5 and 4.3 J/cm(2), respectively, using an MTT assay. This light source was also effective in the DMBA-induced hamster buccal pouch carcinoma model, and in the patients of oral leukoplakia.

CONCLUSIONS

ALA-PDT is effective for premalignant lesions such as mucosal dysplasia and carcinoma in situ of oral cavity. Good results could be obtained by using the homemade LED array as light source. The LED array has the advantages of low cost, high reliability, and portability. It is safe, convenient and easy to use for the treatment of oral dysplasia.

Photodynamic therapy (PDT) using topically applied delta-aminolevulinic acid (ALA) for the treatment of oral leukoplakia

BACKGROUND

Photodynamic therapy (PDT) is a non-invasive method for topical and selective treatment of pre-malignant lesions of oral cavity. The aim of our study was to determine therapeutic response to PDT in patients with oral leukoplakia.

METHODS

Twelve patients participated in our study. Lesions affected a variety of intraoral sites. The most common location was buccal, gingival and mandibular mucosa. Patients were treated with topically applied 10% delta-aminolevulinic acid (ALA) and light from an argon-pumped dye laser. Irradiation was performed in several (6-8) sessions using light at 635 nm wavelength, delivering a total dose of 100 J/cm2 per session.

RESULTS

A complete response was obtained in 10 out of 12 treated patients. One recurrence was observed during 6 months.

CONCLUSION

Photodynamic therapy appears to be a feasible alternative to conventional therapy of pre-malignant lesions of oral cavity.

Fiber optic probes for biomedical optical spectroscopy

Fiber optic probes are a key element for biomedical spectroscopic sensing. We review the use of fiber optic probes for optical spectroscopy, focusing on applications in turbid media, such as tissue. The design of probes for reflectance, polarized reflectance, fluorescence, and Raman spectroscopy is illustrated. We cover universal design principles as well as technologies for beam deflecting and reshaping.

Photodynamic therapy and the alimentary tract

Photodynamic therapy offers the possibility of relatively selective tumour necrosis and normal tissue healing. It has many potential applications but as yet no clear role. Articles, editorials and case reports published primarily in English and listed in Medline/ISI up to April 2000 or identified by a manual search have been reviewed in an attempt to provide a comprehensive overview of the use of photodynamic therapy in the alimentary tract. It is concluded that photodynamic therapy can be an effective treatment for superficial pre-malignant mucosal lesions and early cancers, especially in diffuse disease. Suitable patients include those wishing to avoid surgery, high risk subjects or those in whom other forms of treatment have failed. Superiority over other methods of ablation has not so far been demonstrated. Cheaper and more effective photosensitizers and improved techniques of light delivery are likely to increase the application of photodynamic therapy.

Reactive oxygen-dependent production of novel photochemotherapeutic agents

The reactive nature of species derived from oxygen, such as singlet oxygen and hydrogen peroxide, has been exploited in the clinical setting for targeting bacteria, viruses, and tumor cells by photodynamic excitation of a variety of chromophores. This modality, termed photodynamic therapy (PDT), is currently being used to treat some forms of cancer. However, the applicability of conventional PDT is limited due to the absolute dependence on simultaneous exposure of the target to the photoactive compound and light. In 1990, we demonstrated that the need for simultaneous exposure of the biological target to light and photosensitizer could be circumvented by prior exposure (activation) of the sensitizer molecule to light and its subsequent use as any other anti-cancer or anti-viral drug. By dint of the nature of the protocol, this process was termed preactivation. Since then, the generation of biologically active molecules in vitro by preactivation has been validated using a variety of chromophores, such as merocyanine 540, Photofrin II, and naphthalimide. Here we briefly review the role of reactive oxygen species in the photodynamic effect, and provide an explanation for the mechanism of preactivation. We propose that photo-oxidation not only provides a novel means for the generation of biologically active molecules, but could also explain, at least in part the mechanism of conventional PDT. It is likely that the light-dependent breakdown of the chromophore to generate novel active compounds, in addition to reactive oxygen species, also contributes to the photodynamic damage observed on simultaneous exposure of the chromophore and target tissue to light during PDT.-Pervaiz, S. Reactive oxygen-dependent production of novel photochemotherapeutic agents.

Effect of photodynamic therapy on a heterotransplanted human parotid tumor

To evaluate the effect of photodynamic therapy on human parotid tumors we used tumor specimens obtained from parotid surgery on a consecutive group of patients. The tumors were transplanted into a subcutaneous pocket of nude mice. The original human tumors were pleomorphic adenoma (four), adenolymphoma (one), acinic cell carcinoma (one), sarcoma (one) and low-grade adenocarcinoma (one). The most aggressive growth was seen in the low-grade adenocarcinoma. We re-implanted this tumor on ten mice bilaterally, and treated the tumors with photodynamic therapy (PDT), resulting in a mean depth of tumor necrosis of 5.4 mm (1-10 mm). In three cases we found vital tumor cells in the periphery of the tumor after treatment, with several new blood vessels in the surrounding tissue, indicating a great potential for neo-angiogenesis in this tumor. In order to evaluate the possible nerve damage subsequent to the photodynamic therapy, the ischiadic nerve in 24 lower limbs of nude mice were investigated. In one case only the macroscopical and histological investigation revealed signs of nerve damage. The current study demonstrates that the nude mice implantation model is excellent to investigate growth in both malignant and benign parotid tumors, and to test new therapeutic modalities. Photodynamic therapy seems to have a possible role in the future management of the malignant lesions of the parotid gland, in cases where radical surgery for some reason is not achievable.

Outcome of patients receiving photodynamic therapy for early esophageal cancer

PURPOSE

Photodynamic therapy (PDT) has shown remarkable activity in a variety of human cancers. In the present study, we report the effects of PDT on inoperable early-stage esophageal cancer.

METHODS AND MATERIALS

Sixty-two patients were treated with an argon dye laser (630 nm wavelength, 300-800 mW of power, energy dose of 200-300 J/cm) after intravenous injection of 5 mg/kg of hematoporphyrin derivative. Eighteen patients (29.5%) had in situ carcinoma (Tis), 30 (48.5%) had T1-stage cancer, 7 (11%) had T2-stage cancer, and 7 (11%) had recurrent disease in the anastomotic area after previous surgery without evidence of invasion outside the lumen. Patients with residual disease after two rounds of PDT received definitive radiotherapy. Patients were evaluated for response to therapy and survival. The follow-up time ranged from 3 to 90 months (median, 32 months).

RESULTS

The complete response (CR) rate was 37% (23 of 62) in patients who received PDT alone and 82% (51 of 62) in those who also received radiotherapy. The CR rate after PDT alone was statistically higher (p = 0.04) for patients who had Tis/T1 lesions (21 of 48; 44%) than for those with T2-stage disease (2 of 7; 28%) or recurrent tumors (0 of 7; 0%). Fifty-two percent of patients who had CR following PDT alone did not suffer local tumor recurrence. The median local progression-free survival times after PDT and additional radiotherapy (in cases with incomplete response) was 49 months for Tis- and T1-stage lesions, 30 months for those with T2-stage disease, and 14 months for patients with locally recurrent disease. Patients who completely responded to PDT had a median overall survival (OS) of 50 months, which was significantly longer (p < 0.003) than that of patients not responding to PDT. Toxicity was minimal; we recorded three cases of esophageal stenosis (7%) and one case of tracheo-esophageal fistula (2.5%) after combined PDT and radiotherapy.

CONCLUSION

PDT is an effective regimen for early esophageal cancer, giving a CR rate of about 40%, long-term local control and favorable overall survival. Additional radiotherapy in cases of incomplete response to PDT is effective and potentially curative in another 45% of cases.

An in vitro study of the use of photodynamic therapy for the treatment of natural oral plaque biofilms formed in vivo

Seven-day oral plaque biofilms have been formed on natural enamel surfaces in vivo using a previously reported in situ device. The devices are then incubated with a cationic Zn(II) phthalocyanine photosensitizer and irradiated with white light. Confocal scanning laser microscopy (CSLM) of the biofilms shows that the photosensitizer is taken up into the biomass of the biofilm and that significant cell death is caused by photodynamic therapy (PDT). In addition, the treated biofilms are much thinner than the control samples and demonstrate a different structure from the control samples, with little evidence of channels and a less dense biomass. Transmission electron microscopy (TEM) of the in vivo-formed plaque biofilms reveals considerable damage to bacteria in the biofilm, vacuolation of the cytoplasm and membrane damage being clearly visible after PDT. These results clearly demonstrate the potential value of PDT in the management of oral biofilms.

Oral leukoplakia: a clinicopathological review

Leukoplakia is the most common premalignant or potentially malignant lesion of the oral mucosa. It seems preferable to use the term leukoplakia as a clinical term only. When a biopsy is taken, the term leukoplakia should be replaced by the diagnosis obtained histologically. The annual percentage of malignant transformation varies in different parts of the world, probably as a result of differences in tobacco and dietary habits. Although epithelial dysplasia is an important predictive factor of malignant transformation, it should be realized that not all dysplastic lesions will become malignant. On the other hand non-dysplastic lesions may become malignant as well. In some parts of the world the tongue and the floor of the mouth can be considered to be high-risk sites with regard to malignant transformation of leukoplakia, while this does not have to be the case in other parts of the world. The cessation of tobacco habits, being the most common known aetiological factor of oral leukoplakia, has been shown to be an effective measure with regard to the incidence of leukoplakia and, thereby, the incidence of oral cancer as well. Screening for oral precancer may be indicated in individuals at risk.