The clinical efficacy of topical methyl-aminolevulinate photodynamic therapy in moderate to severe actinic keratoses of the face and scalp

Photodynamic Therapy for Field Cancerization in the Skin: Where Do We Stand?

INTRODUCTION

Photodynamic therapy (PDT) with a photosensitizer is available for the treatment of multiple actinic keratoses (AKs) in a restricted skin area or, as it is established, for the field-cancerized skin.

OBJECTIVES

Our review aims to present the up-to-date literature on skin field cancerization using PDT employing different topical photosensitizers, modified light delivery protocols and combination treatments to obtain excellent efficacy and safety in everyday clinical practice.

METHODS

We sought PubMed, MEDLINE, Scopus, OVID, Embase, Science Direct, Cochrane Library, Research Gate and Google Scholar for [(aminolevulinic acid OR aminolevulinate) AND photodynamic therapy] with (field-directed OR field cancerization, (actinic keratosis), and (efficacy OR effectiveness OR pain OR tolerability) for studies published until February 2023.

RESULTS

Advantages of PDT compared to the other field treatments, including imiquimod, 5-fluorouracil, ingenol mebutate gel and diclofenac, reported better cosmetic outcomes and greater patient satisfaction. On the other hand, some drawbacks of field PDT include pain and treatment duration. Alternate illumination methods have also been investigated, including daylight as a light source. Pretreating the affected area may enhance photosensitizer absorption leading to better therapeutic results, while combinational treatments have also been tested. Patients prefer daylight PDT to traditional light sources since it is more well-tolerated and equally effective. Even as a preventive treatment, field PDT yields promising outcomes, especially for high-risk individuals, including organ transplant recipients.

CONCLUSIONS

This review provides a thorough display of the field of PDT on cancerized skin, which will facilitate physicians in applying PDT more efficiently and intuitively.

Photodynamic therapy: A targeted literature review focussing on outcomes and optimisation in solid organ transplant recipients

Squamous cell carcinoma incidence is 65- to 250-fold in solid organ transplant recipients, BCC is 10-fold and in Australia, rates of skin cancer in solid organ transplant recipients reach 70-82% prevalence within the first 20 years; hence, effective, evidence-based treatment of early and precancerous lesions is an essential tool in dermatological patient care. Photodynamic therapy is used to treat a range of conditions including actinic keratoses, squamous cell carcinoma in situ, superficial basal cell carcinoma and nodular basal cell carcinoma. A literature review was undertaken to examine the outcomes of photodynamic therapy in solid organ transplant recipients and methods of optimising outcomes in solid organ transplant recipients. Study sizes were small and protocols varied widely, so meta-analysis was not possible; however, photodynamic therapy appears to be an acceptable treatment for approved indications in solid organ transplant recipients in whom ongoing surveillance is maintained to ensure clearance and detect recurrence. Methods for improving efficacy were also reviewed for this population. Improved outcomes may be achieved by combining photodynamic therapy with other local methods such as 5-fluorouracil or ablative fractional laser.

Non-melanoma Skin Cancer in Canada Chapter 3: Management of Actinic Keratoses

Background

Actinic keratosis (AK) and cheilitis (AC) are lesions that develop on photodamaged skin and may progress to form invasive squamous cell carcinomas (SCCs).

Objective

To provide guidance to Canadian health care practitioners regarding management of AKs and ACs.

Methods

Literature searches and development of graded recommendations were carried out as discussed in the accompanying introduction (chapter 1 of the NMSC guidelines).

Results

Treatment of AKs allows for secondary prevention of skin cancer in sun-damaged skin. Because it is impossible to predict whether a given AK will regress, persist, or progress, AKs should ideally be treated. This chapter discusses options for the management of AKs and ACs.

Conclusions

Treatment options include surgical removal, topical treatment, and photodynamic therapy. Combined modalities may be used in case of inadequate response. AKs are particularly common following the longterm immunosuppression in organ transplant patients, who should be monitored frequently to identify emerging lesions that require surgery.

Cutaneous field cancerization: clinical, histopathological and therapeutic aspects

The concept of "field cancerization" was first introduced by Slaughter in 1953 when studying the presence of histologically abnormal tissue surrounding oral squamous cell carcinoma. It was proposed to explain the development of multiple primary tumors and locally recurrent cancer. Organ systems in which field cancerization has been described since then are: head and neck (oral cavity, oropharynx, and larynx), lung, vulva, esophagus, cervix, breast, skin, colon, and bladder. Recent molecular studies support the carcinogenesis model in which the development of a field with genetically altered cells plays a central role. An important clinical implication is that fields often remain after the surgery for the primary tumor and may lead to new cancers, designated presently as "a second primary tumor" or "local recurrence," depending on the exact site and time interval. In conclusion, the development of an expanding pre-neoplastic field appears to be a critical step in epithelial carcinogenesis with important clinical consequences. Diagnosis and treatment of epithelial cancers should not only be focused on the tumor but also on the field from which it developed. The most important etiopathogenetic, clinical, histopathological and therapeutic aspects of field cancerization are reviewed in this article.

Fractional laser-assisted delivery of methyl aminolevulinate: Impact of laser channel depth and incubation time

BACKGROUND AND OBJECTIVES

Pretreatment of skin with ablative fractional lasers (AFXL) enhances the uptake of topical photosensitizers used in photodynamic therapy (PDT). Distribution of photosensitizer into skin layers may depend on depth of laser channels and incubation time. This study evaluates whether depth of intradermal laser channels and incubation time may affect AFXL-assisted delivery of methyl aminolevulinate (MAL).

MATERIALS AND METHODS

Yorkshire swine were treated with CO2 AFXL at energy levels of 37, 190, and 380 mJ/laser channel and subsequent application of MAL cream (Metvix) for 30, 60, 120, and 180 minutes incubation time. Fluorescence photography and fluorescence microscopy quantified MAL-induced porphyrin fluorescence (PpIX) at the skin surface and at five specific skin depths (120, 500, 1,000, 1,500, and 1,800 µm).

RESULTS

Laser channels penetrated into superficial (∼300 µm), mid (∼1,400 µm), and deep dermis/upper subcutaneous fat layer (∼2,100 µm). Similar fluorescence intensities were induced at the skin surface and throughout skin layers independent of laser channel depth (180 minutes; P < 0.19). AFXL accelerated PpIX fluorescence from skin surface to deep dermis. After laser exposure and 60 minutes MAL incubation, surface fluorescence was significantly higher compared to intact, not laser-exposed skin at 180 minutes (AFXL-MAL 60 minutes vs. MAL 180 minutes, 69.16 a.u. vs. 23.49 a.u.; P < 0.01). Through all skin layers (120-1,800 µm), laser exposure and 120 minutes MAL incubation induced significantly higher fluorescence intensities in HF and dermis than non-laser exposed sites at 180 minutes (1,800 µm, AFXL-MAL 120 minutes vs. MAL 180 minutes, HF 14.76 a.u. vs. 6.69 a.u. and dermis 6.98 a.u. vs. 5.87 a.u.; P < 0.01).

CONCLUSIONS

AFXL pretreatment accelerates PpIX accumulation, but intradermal depth of laser channels does not affect porphyrin accumulation. Further studies are required to examine these findings in clinical trials.

Clinical, histopathological and immunohistochemical assessment of human skin field cancerization before and after photodynamic therapy

BACKGROUND

The field cancerization concept in photodamaged patients suggests that the entire sun-exposed surface of the skin has an increased risk for the development of (pre)-malignant lesions, mainly epithelial tumours. Topical photodynamic therapy (PDT) is a noninvasive therapeutic method for multiple actinic keratosis (AK) with excellent outcome.

OBJECTIVES

To evaluate the clinical, histological and immunohistochemical changes in human skin with field cancerization after multiple sessions of PDT with methyl-aminolaevulinate (MAL).

METHODS

Twenty-six patients with photodamaged skin and multiple AK on the face received three consecutive sessions of MAL-PDT with red light (37 J cm(-2)), 1 month apart. Biopsies before and 3 months after the last treatment session were taken from normal-appearing skin on the field-cancerized area. Immunohistochemical stainings were performed for TP-53, procollagen-I, metalloproteinase-1 (MMP-1) and tenascin-C (Tn-C).

RESULTS

All 26 patients completed the study. The global score for photodamage improved considerably in all patients (P < 0·001). The AK clearance rate was 89·5% at the end of the study. Two treatment sessions were as effective as three MAL-PDT sessions. A significant decrease in atypia grade and extent of keratinocyte atypia was observed histologically (P < 0·001). Also, a significant increase in collagen deposition (P = 0·001) and improvement of solar elastosis (P = 0·002) were noticed after PDT. However, immunohistochemistry showed only a trend for decreased TP-53 expression (not significant), increased procollagen-I and MMP-1 expressions (not significant) and an increased expression of Tn-C (P = 0·024).

CONCLUSIONS

Clinical and histological improvement in field cancerization after multiple sessions of MAL-PDT is proven. The decrease in severity and extent of keratinocyte atypia associated with a decreased expression of TP-53 suggest a reduced carcinogenic potential of the sun-damaged area. The significant increase of new collagen deposition and the reduction of solar elastosis explain the clinical improvement of photodamaged skin.

Photodynamic therapy for skin field cancerization: an international consensus. International Society for Photodynamic Therapy in Dermatology

Field cancerization is a term that describes the presence of genetic abnormalities in a tissue chronically exposed to a carcinogen. These abnormalities are responsible for the presence of multilocular clinical and sub-clinical cancerous lesions that explains the increased risks of multiple cancers in this area. With respect to the skin, this term is used to define the presence of multiple non-melanoma skin cancer, its precursors, actinic keratoses and dysplastic keratinocytes in sun exposed areas. The multiplicity of the lesions and the extent of the area influence the treatment decision. Providing at least equivalent efficacy and tolerability, field directed therapies are therefore often more worthwhile than lesion targeted approaches. Photodynamic therapy (PDT) with its selective sensitization and destruction of diseased tissue is one ideal form of therapy for this indication. In the following paper the use of PDT for the treatment of field cancerized skin is reviewed and recommendations are given for its use.