An ultrasound analysis of the response of Gorlin syndrome-related and sporadic basal cell carcinomas to aminolaevulinic acid photodynamic therapy

SUMMARY 

Background:

Gorlin Syndrome (naevoid basal cell carcinoma syndrome, NBCCS) predisposes the patient to the development of basal cell carcinomas (BCCs) throughout their life. The standard treatment for isolated lesions is surgical excision. However, when numerous surgical procedures are required over time, the patient can be left with multiple disfiguring scars. Photodynamic therapy (PDT) offers a non-invasive treatment option for patients with this condition, in which ionizing radiation is contraindicated. This study evaluates PDT as a treatment modality for Gorlin Syndrome and compares the treatment response of Gorlin-related basal cell carcinomas with that of the sporadic lesions.

Methods

: In this un-randomized study, basal cell carcinomas in 25 Gorlin syndrome patients (with 36 lesions) and 145 sporadic patients (with 189 lesions) were treated by photodynamic therapy, using δ-5-aminolaevulinic acid (ALA) as a photosensitizer and 100Jcm⁻² of red light (630±15nm). The maximum thickness of the BCC was measured by 20MHz pulsed ultrasound prior to treatment and again 4–6 weeks and 12 months following treatment. The response of Gorlin syndrome lesions was compared to those in the overall sporadic population and then to a subpopulation matched as closely as possible for age, lesion thickness and site.

Results:

For both populations, the average pre-treatment BCC thickness by US was 1.5mm (overall range 0.3–5.3), and the average thickness at 4–6 weeks post-treatment was 0.5mm (overall range 0–4.3). Those BCC less than 1.5mm thick prior to treatment were significantly more likely to have no US evidence of disease at 4–6 weeks than and were more likely to be controlled at 12 months.

Conclusions:

The average response to ALA PDT of Gorlin syndrome-related BCC closely resembles that for the sporadic population, with the same wide range of responses for a given dose. Ultrasound parameters measured at treatment and at 4–6 weeks post-treatment aid prediction of outcome and necessity for further treatment.

Keywords: Pulsed ultrasound, Aminolaevulinic acid, Photodynamic therapy, Basal cell carcinoma, Gorlin syndrome, Nevoid basal cell carcinoma syndrome