Dynamic optical coherence tomography evaluation in locally advanced basal cell carcinoma during sonidegib treatment

Basal cell carcinoma (BCC) is the most common cancer in the Caucasian population. It has a multifactorial pathogenesis, in which constitutive activation of the Sonic Hedgehog signalling (SHH) pathway (via mutations in PTCH1 or SMO genes) represents by far the most common genetic aberration. The introduction of vismodegib and sonidegib, two SHH pathway inhibitors, changed the therapeutic approach of locally advanced and metastatic BCCs. EADO's (European Association of Dermato-Oncology) new staging system refers to these as 'difficult-to-treat' BCCs.

The aim was to evaluate sonidegib's effectiveness in patients affected by difficult-to-treat BCCs by using non-invasive diagnostic techniques.

We retrospectively evaluated 14 patients (4 females, 10 males; mean age 77 ± 11 years) affected by difficult-to-treat BCCs treated with oral sonidegib 200 mg/day that were followed with total body videodermoscopy (V-Track, Vidix 4.0) and dynamic optical coherence tomography (D-OCT, VivoSight Dx) since May 2022. Considering the risk of rhabdomyolysis routine blood tests, especially for creatine kinase concentrations, were performed. All treated patients were inserted in the BasoCare database, which aims to offer support to patients taking sonidegib. Complete and partial responses were evaluated by the overall reduction of the number of lesions and their individual sizes. Safety was evaluated by assessing the occurrence and severity of adverse reactions.

Eighty per cent achieved complete clearance and 75% reduction of diameter. D-OCT scans performed at every follow-up showed concordance with clinical appearance and demonstrated reduction of hyporeflective structures, that is, islets of tumour cells and overall improvement of morphology.

Sonidegib can be considered an effective treatment option in cases where surgery or radiotherapy would be unfeasible or has previously failed, although pigmented lesions did not show complete clearance, suggesting that there are factors other than the SHH pathway involved in tumour growth. Videodermoscopy and D-OCT were useful in the quick and seamless follow-up of lesions and added valuable information in assessing efficacy.