Introduction to laser treatment of basal cell carcinomas

Basal cell carcinoma (BCC) is a non-melanoma skin cancer (NMSC). One of the latest non-invasive methods of NMSC treatment is by laser ablation and photodynamic therapy (PDT). The two are a much sought after non-surgical option for NMSCs like basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and actinic keratoses (AKs). Among the variety of lasers that have been developed for the treatment of diseases afflicting various body organs, non-coherent light sources and laser-assisted PDT has been the most common treatment forms for NMSCs.

Photodynamic therapy (PDT)

PDT is a most updated treatment regimen for NMSCs (including BCC) that initially involved the use of photosensitizing drugs and light. Later penetration enhancers were also added to the treatment regimen for the destruction of cancer cells.

PDT was first researched as a way to destroy malignant tissues in the beginning of the 20th century. It began as a combination of systemic photosensitizing medication, light and oxygen and was implemented for the treatment of tumors in various body organs. When compared to surgical methods, PDT had the advantage of clearing tumors with satisfactory cosmetic outcomes and no marked scars, substantial patient comfort and short restorative period. However, it had the disadvantage of long-term phototoxicity due to the use of systemic photosensitizers.

In 1990, when 5-aminolevulinic acid (ALA) and methylester of ALA (mALA), both potent topical photo-sensitizers, were developed and introduced to the PDT therapy for skin cancers, the disadvantage of phototoxicity was considerably reduced. Topical 5-ALA-PDT proved really beneficial in the treatment of NMSC without the side effects of phototoxicity. However, there have been no systematic published studies comparing ALA-PDT with standard surgery, electrodesiccation and curettage, irradiation, or topical cytotoxic agents.

The light component in PDT has originally been large and intricate lasers. Currently a variety of coherent and non-coherent light sources are used.

Most common ones are:

• Dye lasers assisted by argon or metal vapor lasers
• Frequency-doubled Nd:YAG lasers
• The most recent femtosecond lasers

Non-laser lights like tungsten filament, xenon arc, metal halide, and fluorescent lamps are also used. The latest additions have been light-emitting diodes.

Disadvantages of these light sources pertain to the degree of penetration, spot size and lack of definite parameters so far as the most effective syndrome-based irradiance, wavelength of the light and dosage suitable for various light forms are concerned. Side effects in case of BCC are generally pain, though anesthesia is not required.

A certain study group also pointed out the disadvantage of using coherent and incoherent light sources for the therapy of large or multiple BCCs. The most common drawbacks were tedious treatment period and soaring overhead expenses. PDT for BCC has also been considered best suited for tumor cells.

CO2 lasers

Studies regarding CO2 laser therapy for the treatment of BCC are small and there are no available published reports based on large-scale research. The small studies have suggested partial effectiveness of this treatment mode and most have reported no major side effects. In fact, the success rate is pegged at 100% clearance of superficial BCCs when ablation is achieved till the middermis. Most have also reported that CO2 laser therapy was comparatively speedier and cheaper than standard surgical procedures.

Effectiveness of laser assisted treatment of basal cell carcinomas

However, there are still no conclusive results available so far as the specific function of laser and light-emitting sources either used alone or in combination with photodynamic therapy (PDT), for the treatment of nonmelanoma skin cancers (NMSCs). Various studies have been conducted over decades with varying results.

Moreover, the exact degree of clearance achieved and recurrence of superficial and nodular BCC and SCC after laser and PDT therapy are also unknown. Some studies have suggested that PDT may have the potential of a clearance quotient similar to BCC treatment with radiation. But one thing is for certain, that despite technological advancements, PDT treatment of BCC is still less effective than surgical removal and Mohs surgery so far as reappearance rates are concerned. Statistics report that in the latter it is less than 10%. Hence, it is advised that laser and PDT should be applicable only for patients whose condition cannot be managed with standard surgical therapy procedures for BCC and SCC.

5-aminolevulinic acid–PDT is somewhat better rated when used in combination with penetration enhancers and given in multiple treatment sessions for BCC treatment. Research is on to develop more effective light sources and photosensitizers for treatment of BCC and other NMSCs.

Though, laser and PDT therapy have brought new hope in the treatment of NMSCs like BCC, especially for patients with multiple or large NMSCs or for whom surgery is difficult, there needs to be more definite research about their effectiveness and functionality.