|Year : 2015 | Volume
| Issue : 2 | Page : 464-467
Treatment of oral leukoplakia with photodynamic therapy: A pilot study
Niranzena Panneer Selvam1, Jayachandran Sadaksharam1, Ganesan Singaravelu2, Rajasekaran Ramu2
1 Department of Oral Medicine and Radiology, Tamil Nadu Government Dental College and Hospital, Chennai, Tamil Nadu, India
2 Department of Medical Physics, Anna University, Chennai, Tamil Nadu, India
|Date of Web Publication||7-Jul-2015|
Niranzena Panneer Selvam
Department of Oral Medicine and Radiology, Tamil Nadu Government Dental College and Hospital, Park Town, Chennai - 600 003, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Aim of the Study: Oral leukoplakia (OL) is the most common potentially malignant disorder that may transform into oral carcinoma. By treating leukoplakia in its incipient stage, the risk of occurrence of oral carcinoma can be prevented. In this aspect, photodynamic therapy (PDT) can serve as a useful treatment modality. The aim of the study is to treat patients with OL using PDT in which 5-aminolevulinic acid (ALA) is used as a photosensitizer.
Materials and Methods: Five patients with OL were included in the study. They were treated with 10% ALA mediated PDT (light source: Xenon lamp, power: 0.1 W, wavelength: 630 ± 5 nm, total dose: 100 J/cm 2 per session) for 6-8 sessions. Follow-up was done for a period of 1 year.
Results: One month (4 weeks) after ALA-PDT, the response was evaluated based on clinical examination. It was as follows: Complete response: Two patients; partial response: Two patients; and no response: One patient. There was no recurrence in any of the cases.
Conclusion: There was satisfactory reduction in the size of the OL lesion without any side-effects. Thus, ALA mediated PDT seems to be a promising alternative for the treatment of OL.
Keywords: 5-Aminolevulinic acid, leukoplakia, photodynamic therapy, potentially malignant disorders
|How to cite this article:|
Selvam NP, Sadaksharam J, Singaravelu G, Ramu R. Treatment of oral leukoplakia with photodynamic therapy: A pilot study. J Can Res Ther 2015;11:464-7
| > Introduction|| |
Oral leukoplakia (OL) is a common potentially malignant disorder that may transform into oral carcinoma. It accounts for over 80% of potentially malignant oral disorders.  Worldwide there is a rise in the habit of using tobacco in both smoking and smokeless form. This has led to an increase in the incidence of OL. Malignant transformation of leukoplakia may occur in 0.3-25% of individuals. The presence of dysplasia increases the occurrence of malignancy by 30%. 
By treating leukoplakia in the incipient stage, the incidence of oral carcinoma can be brought down to a great extent. Various modalities to manage leukoplakia, including the use of antioxidants such as vitamin A, C and E, analogues of vitamin A and beta-carotene, surgical excision, electrocautery, cryotherapy and laser ablation have been proposed. However from time innumerable, there has been a search for a noninvasive treatment modality for leukoplakia. Photodynamic therapy (PDT) has been proved successful in this aspect. It overweighs conventional treatments in being noninvasive; produces good cosmetic results; well-tolerated by patients; can be used to patients where surgery is contraindicated or those who have pacemakers and bleeding disorders; and does not have cumulative toxicity. 
Photodynamic therapy has been used for a variety of malignancies including those found in the lung, esophagus, colon, peritoneum, pleura, genitourinary tract, brain, eye, and skin.  Clinical studies confirm high effectiveness of PDT in the treatment of early neoplastic and preneoplastic pathologies within oral mucosa. Although not a huge number of patients reported in the literature have undergone PDT, the results are promising.  The aim of this study is to treat patients with OL using PDT in which aminolevulinic acid (ALA) is used as a photosensitizer.
| > Materials and methods|| |
Totally five patients with OL (homogenous type - three cases [Figure 1]a; verrucous type - one case; erythroleukoplakia - one case [Figure 2]a) were recruited for the study. The Institute's Ethical Committee approval was obtained. The study was conducted in full accordance with ethical principles, including the World Medical Association Declaration of Helsinki (version, 2002). All the patients who came to the outpatient ward of our department between June and July 2012 were screened, and only those patients with clinically, and histologically proven OL was included under the study. Local risk factors for the development of leukoplakia like sharp tooth edges, large amalgam fillings or inadequate dental prostheses were excluded. Those with chronic systemic diseases, photosensitivity and histologically proven malignant changes in the lesion were excluded. All the patients had the habit of using tobacco in smoking or smokeless form. The patients underwent tobacco cessation counseling and oral prophylaxis 3 months prior to the therapy, but there was no change in the size of the lesion.
|Figure 1: Clinical photographs of patient with homogenous leukoplakia before and after aminolevulinic acid (ALA)-photodynamic therapy (PDT). (a) Homogenous leukoplakia lesion on buccal aspect of right maxillary gingiva before ALA-PDT. (b) Same region 4 weeks after completion of ALA-PDT showing no remaining signs of the lesion|
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|Figure 2: Clinical photographs of patient with erythroleukoplakia before and after aminolevulinic acid (ALA)-photodynamic therapy (PDT). (a) Erythroleukoplakia present on right buccal mucosa before ALA-PDT. (b) Same region 4 weeks after completion of ALA-PDT showing no remaining signs of the lesion|
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Informed consent was obtained. On the first visit, thorough clinical examination was done, and the details were recorded on the structured proforma. Biopsy was performed, and the clinical diagnosis was confirmed histopathologically. On the second visit, we determined when the protoporphyrin IX (Pp IX) reached its peak level in the lesion by ALA-induced Pp IX fluorescence spectroscopy. We found out that the accumulation of Pp IX in the lesion achieved its peak approximately at the end of 3 rd h after ALA application in almost all the patients.
On the third visit, the therapy was performed at the Department of Medical Physics, Anna University, Chennai, India. 10% ALA emulsion (0.1 g of 99.9% ALA powder [Acros Organics and Maybridge, Belgium] in 1 ml liquid paraffin) was freshly prepared in a darkened room just before the start of the therapy to avoid deterioration of the emulsion on contact with light. The lesion was exactly measured and photographed. Then the lesion was isolated using cotton rolls to control the flow of saliva. ALA emulsion was applied on the lesion using a paint brush. A gauze pad soaked in ALA emulsion was then placed over the lesion to avoid salivary contamination. The therapy (light application) was started at the end of 3 h in accordance with the peak accumulation of Pp IX. Xenon lamp (ISA-SPEX, Jobin Yvon-Spex, Edison, NJ, USA) with power -0.1 W, wavelength -630 ± 5 nm was used as the light source. The light application composed of multiple 3-min irradiations for a total of 1000 s interspersed by several 3-min rests. The light emitting probe was placed as close as possible to the lesion. A rest period of 3 min was given to provide the patients a break from holding their mouth open for a longer period. Total dose delivered per session was 100 J/cm 2 . The therapy was performed for 6-8 sessions at an interval of 1 week between each session. Photographs were taken before and after treatment and during the follow-up visits.
The patients were recalled at 4 weeks after completion of the last session of light therapy. The lesion was examined clinically. Lesion response was characterized as follows: Complete response (CR), lack of detectable lesion confirmed by clinical evaluation; partial response (PR), reduction of the lesion by at least 20% in diameter; no response (NR), reduction of lesion by < 20% in diameter.  The patients were followed-up for a period of 1 year after treatment to rule out any recurrence.
| > Results|| |
One month (4 weeks) after ALA-PDT, the response was evaluated based on clinical examination. [Table 1] shows the clinicopathological data and response for ALA-PDT among the five patients. CR was obtained in 2 out of 5 patients [Figure 1]b and [Figure 2]b; PR in 2 out of 5 patients; and NR in 1 patient [Table 1]. During the follow-up, no changes in the clinical appearance of the treated lesions were recorded. There was no recurrence of the lesion noted in CR cases. During the incubation period of 3 h after ALA application, the patients did not have any adverse effect in the form of pain, redness or discomfort. During the course of light irradiation, two patients developed mild burning sensation which disappeared immediately after light application. There was no need for the use of local anesthesia or analgesics in our study. Apart from this, patients did not have any other side effects.
|Table 1: Clinicopathological data and results of ALA - PDT of the patients|
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| > Discussion|| |
Photodynamic therapy is one of the latest methods to treat various kinds of tumors. It produces cellular and tissue destruction in an oxygen-dependent manner with the help of two individually nontoxic components, light and photosensitizer. It works on the basis of administration of an exogenous photosensitizer to leave the tumor tissue sensitive to light of a specific wavelength. The photosensitizers are inert substances that have a selective affinity to tumor tissues. When light of a specific wavelength activates the photosensitizer trapped by the tumor cells, energy from the light is transferred to molecular oxygen, resulting in the production of reactive oxygen species (ROS). PDT involves three main mechanisms to induce tumor destruction. First, direct killing of tumor cells by the ROS; secondly, damage the vasculature associated with tumor, leading to thrombus formation and subsequent tumor infarction; thirdly, activation of an immune response against tumor cells. 
The clinical outcomes were good with regard to PDT with systemically or topically administered ALA when used for the treatment of oral precancer and cancer.  ALA itself is not a photosensitizer but serves as the biological precursor of the photosensitizer, Pp IX, in the heme biosynthesis pathway. There are two rate-limiting steps in this pathway. One is the first step of forming ALA from glycine and succinyl-coenzyme A, which is regulated by heme via negative feedback mechanism. The other rate-limiting step is the conversion of Pp IX to heme, and this process is controlled by the ferrochelatase, which adds a ferrous iron to Pp IX to form the heme. Exogenous ALA administration short-circuits the first step of porphyrin synthesis and subsequently leads to the accumulation of Pp IX in the tissue. Furthermore, Pp IX accumulation could be the result of a decreased conversion of Pp IX to heme in tumor cells as a result of a decreased ferrochelatase activity. 
In the field of PDT, ALA is unique as being the only photosensitizer which can produce reliable photosensitization when administered orally or topically. The maximum tissue concentration of Pp IX in the lesion varied among various studies and to the extent it depended on the concentration of ALA used. Kübler et al., when treating OL with 20% ALA found maximum tissue concentration of Pp IX to be after 2 h,  while Chen et al. , and Lin et al.  found it to be 1.5 h after 20% ALA application. Sieron et al. performed PDT with 10% ALA at the end of 4 h after ALA application.  In our study, we found that Pp IX reached its maximum level in the lesion 3 h after local 10% ALA application. Thus, maximum tissue concentrations of Pp IX are obtained within 4 h, followed by an almost equal rapid decline. The difference in Pp IX peak accumulation may be due to the different concentrations of ALA being used or due to the difference in the demographic profile of the patients along with variable salivary flow rate. Thus, we recommend determining the peak accumulation of Pp IX for each individual before the start of the therapy. Within 48 h, tissue levels of Pp IX are back to background levels.  Thus, ALA induced Pp IX photosensitization will be cleared within 48 h after topical application. The lack of long lasting photosensitization is a great advantage of ALA over all other photosensitizers. Due to this, patients do not have to take any precautions concerning light and sun exposure after the first 48 h. 
When treating eight oral verrucous hyperplasia (OVH) and 24 OL lesions, Chen et al. demonstrated CR in all OVH lesions and eight of the OL lesions.  Sieron et al. treated 12 patients with OL, out of which 10 had CR.  In the study by Chen et al., totally 24 OVH lesions, 97 OL lesions, and 6 oral erythroleukoplakia (OEL) lesions were treated with topical PDT; of which all 24 OVH lesions, 16 OL lesions and 4 OEL lesions showed CR. They reported that clinically better outcome was achieved when OL lesions were treated with topical PDT twice a week than once a week.  Kübler et al. treated 12 OL patients where CR was noticed in five patients, PR in four patients and the treatment was unsuccessful in three patients.  In the present study, we noticed CR in one case each of homogeneous leukoplakia (HL) and erythroleukoplakia, PR in one case each of HL and verrucous leukoplakia and NR in one case of HL. The variation in various study results can be attributed to the differences in the types of leukoplakia, their site of involvement, concentration of ALA used, number of treatment sessions, incubation period (1.5-5 h), specifications of the light source used and protocol of light delivery (continuous or fractionated).
In comparison with skin, oral mucosa in the absence of the keratin layer facilitates penetration of ALA into the mucosa. A penetration depth of 2 mm can be expected.  In our study, we received CR in one case of homogenous type with mild dysplasia and other case of erythroleukoplakia with moderate dysplasia. Pink to red and dysplastic OL lesions usually have thinner surface keratin layer, leading to diffusion of more ALA into the lesions. Furthermore, dysplastic lesions have more permeable epithelium (due to wide intercellular spaces of the dysplastic epithelium) leading to more ALA diffusion into the lesions. In addition, the dysplastic epithelium may retain more ALA than the hyperplastic epithelium and the thinner keratin layer may only have a minimal effect on the reduction of the light intensity. Furthermore, there are more epithelial cells in the cell division in the dysplastic lesions, which are more susceptible to destruction by PDT.  Thus, in our study, we received good results in lesions with some amount of dysplasia and mixed red and white lesions. Furthermore, there was no CR in lesions >1 cm. This could either be due to the need to have light irradiation at multiple sites in order to cover the entire lesion or insufficient number of sittings.
In the present study, we achieved only PR with respect to the verrucous lesion. This may be attributed to increased thickness of the keratin layer where penetration of ALA becomes difficult. We suggest that this may be overcome by increasing the number of sittings. However, here we were unable to do so due to lack of patient co-operation. Also, there was NR for the lesion present on the ventral surface of the tongue. This may be due to leaching away of ALA by the action of saliva from the salivary ductal opening present in the vicinity.
| > Conclusion|| |
Our observations suggest that topical ALA mediated PDT is a promising means of treating OL. In future, it may be considered as first line of treatment being a noninvasive therapy that can be repeated without any adverse effects. However, we are expanding the study by increasing the sample size so as to validate the proposed treatment.
| > References|| |
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Sieron A, Adamek M, Kawczyk-Krupka A, Mazur S, Ilewicz L. Photodynamic therapy (PDT) using topically applied delta-aminolevulinic acid (ALA) for the treatment of oral leukoplakia. J Oral Pathol Med 2003;32:330-6.
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[Figure 1], [Figure 2]
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