Introduction to laser treatment of squamous cell carcinoma

Squamous Cell Carcinoma or SCC, as well as SCC in situ, also known as Bowen’s disease, have traditionally been treated by cryotherapy, topical fluorouracil, electro dessication and curettage, radiotherapy, excision and laser therapy.

Squamous cell carcinoma (SCC) in situ (Bowen’s disease) laser treatment

In a trial conducted on 13 patients with SCC in situ, the lesions were irradiated with two passes of CO2 laser at 500 mJ and two to four watts. After irradiation, the excised and treated portions were examined. Most of these excised portions revealed residual tumor, indicating that CO2 laser treatment alone was not sufficient to remove all the tumors in SCC lesions that are hyperkeratotic or have follicular extensions.

A small phase I trial was conducted to study the treatment of SCC in situ by topical ALA-PDT 20% cream ointment. Fourteen patients with 36 lesions participated in the study. They were given ALA 20% cream treatment and irradiated with 630nm light from a copper vapor/dye laser at 125 to 250 J/ sq.cm and 150mW/sq.cm. One patient withdrew from the study due to severe pain. At a median follow up of 18 months there was a complete response rate of 89%. The investigators concluded that the results with SCC in situ were encouraging, especially for lesions in older patients with poorly vascularized skin, such as, the ankle and the pretibial area.

Three clinical studies were conducted to investigate the treatment of Squamous Cell Carcinoma in situ by ALA-PDT. The first study compared the efficacy of PDT with that of cryosurgery in the treatment of nineteen patients with forty Squamous Cell Carcinoma in situ lesions. These patients received randomly cryotherapy or ALA- PDT where 20% cream under occlusion was given 4 hours before exposure to light at 630nm and 70mW/sq.cm. On examination, it was found that PDT using a non-laser light source was, as it appeared, as effective as cryotherapy and resulted in fewer adverse effects.

In the second study, an attempt was made to determine the optimal wavelength for ALA-PDT. In this randomized comparison study, red light at 630nm or green light at 540nm was used to treat SCC in situ. Treatments, at either of these two wave lengths, were randomly given to 16 patients with 61 lesions. At the 12-month follow up after treatment, red light with a clearance rate of 88% produced better results than green light with a clearance rate of 48%.

The third and the most recent study was an open design study of ALA-PDT for large or multiple patches of Squamous Cell Carcinoma in situ. In this study, 40 large lesions of sizes greater than 20nm and 45 multiple patches of Squamous Cell Carcinoma in situ were treated with 20% ALA cream under occlusion for 4 to 6 hours before irradiation by a PDT lamp at 630nm and 100J/sq.cm. Examination showed that for large lesions the clearance rate obtained was 79% and for multiple patches the clearance rate was 89%. In view of such highly satisfactory results, it was proposed that PDT be considered as the first option for treating large or multiple lesions in Squamous Cell Carcinoma in situ.

A study was also done to evaluate the efficacy and safety of a new and large field light source for PDT treatment of multiple patches in SCC in situ. Using an incoherent lamp with a diameter of 15cm, 80 lesions were irradiated at 630nm, 105 to 168mW/sq.cm and 105J/sq.cm. Up to four treatments were given. At a follow up of 12 months, the clearance rate obtained was 69%. These clearance rates were found low when compared to clearance rates obtained in previously published studies. But results may not be directly comparable, since the earlier studies involved widely varying lesion sizes and light sources.

Squamous cell carcinoma (SCC) treatment

A retrospective study, investigated the immediate and long term effects of ALA-PDT on superficial SCC. In this study, 23 patients with 35 superficial SCC were treated with ALA 20% cream under occlusion prior to irradiation by either UVA or various wave lengths of polychromatic visible light. At 36 months after therapy, the disease free rate was only 8%. The conclusion drawn was that the outcome of treatment of superficial SCC with topical ALA-PDT with polychromatic light was not satisfactory. It was suggested that in order to increase efficacy of this treatment, superior light sources and penetration enhancers were needed.