Operational classification of cutaneous squamous cell carcinomas based on unsupervised clustering of real cases by experts.

BACKGROUND: There is currently no staging system for cutaneous squamous cell carcinoma (cSCC) that is adapted to decision-making and universally used. Experts have unconscious ability to simplify the heterogeneity of clinical situations into a few relevant groups to drive their therapeutic decisions. Therefore, we have used unsupervised clustering of real cases by experts to generate an operational classification of cSCCs, an approach that was successful for basal cell carcinomas. OBJECTIVE: To generate a consensual and operational classification of cSCCs. METHOD: Unsupervised independent clustering of 248 cases of cSCCs considered difficult-to-treat. Eighteen international experts from different specialties classified these cases into what they considered homogeneous clusters useful for management, each with freedom regarding clustering criteria. Convergences and divergences between clustering were analysed using a similarity matrix, the K-mean approach and the average silhouette method. Mathematical modelling was used to look for the best consensual clustering. The operability of the derived classification was validated on 23 new practitioners. RESULTS: Despite the high heterogeneity of the clinical cases, a mathematical consensus was observed. It was best represented by a partition into five clusters, which appeared a posteriori to describe different clinical scenarios. Applicability of this classification was shown by a good concordance (94%) in the allocation of cases between the new practitioners and the 18 experts. An additional group of easy-to-treat cSCC was included, resulting in a six-group final classification: easy-to-treat/complex to treat due to tumour and/or patient characteristics/multiple/locally advanced/regional disease/visceral metastases. CONCLUSION: Given the methodology based on the convergence of unguided intuitive clustering of cases by experts, this new classification is relevant for clinical practice. It does not compete with staging systems, but they may complement each other, whether the objective is to select the best therapeutic approach in tumour boards or to design homogeneous groups for trials.

Treatment approaches of advanced cutaneous squamous cell carcinoma.

Common primary cutaneous squamous cell carcinoma (CSCC) accounts for 20% of keratinocyte cancers that is usually successfully treated with surgery or radiotherapy. In a minority of cases, CSCC lesions may progress to locally advanced or metastatic disease that may be difficult to be treated causing significant morbidity and mortality. Chemotherapies and targeted therapy with anti-epidermal growth factor receptor antibodies have been used off-label in small studies and case reports of advanced CSCC, but data are scarce and response short-lived. Recently, two PD-1 immune checkpoint inhibitors, cemiplimab and pembrolizumab, have been approved for the treatment of advanced CSCC; specifically the former can be administered in patients with locally advanced and metastatic tumours, while the latter in case of recurrent metastatic CSCC. The introduction of immune checkpoint inhibitors represents a breakthrough in the treatment of CSCC, since numerous clinical trials showed that these agents may provide remarkable clinical benefit with an acceptable safety profile, in a high-need population who had no standard of care. In addition, real-world studies are needed to validate the results observed in clinical trials and numerous clinical trials in the neoadjuvant or adjuvant setting are ongoing. Finally, further studies should investigate predictive biomarkers useful to better select patients to maximize the treatment efficacy.

Molecular genetics of cutaneous squamous cell carcinoma: perspective for treatment strategies.

Cutaneous squamous cell carcinoma (cSCC) represents 20% of all skin cancers. Although primary cSCCs can be successfully treated with surgery, a subset of highly aggressive lesions may progress to advanced disease, representing a public healthcare problem with significant cancer-related morbidity and mortality. A complex network of genes (TP53, CDKN2A, NOTCH1 and NOTCH2, EGFR and TERT) and molecular pathways (RAS/RAF/MEK/ERK and PI3K/AKT/mTOR) have been shown to play an important role in the pathogenesis of cSCC. The epigenetic regulation of TP53 and CDKN2A is an attractive therapeutic target for the treatment of cSCC, as well as NOTCH-activating agents capable to restore its tumour-suppressor function. EGFR inhibitors including both monoclonal antibodies (cetuximab and panitumumab) and tyrosine kinase inhibitors (erlotinib, gefitinib and dasatinib) have been used in clinical trials for the treatment of advanced cSCC, achieving only partial clinical benefit. Recently, an immune-modulatory drug (cemiplimab) has been introduced for the treatment of advanced cSCC with good clinical results and a favourable safety profile, while other PD1/PD-L1 inhibitors, either as monotherapy or in combination with targeted therapies, are currently under investigation. This review focuses on molecular findings involved in the pathogenesis of cSCC and their implications for the future development of new treatment strategies. In addition, current and ongoing treatments on targeted therapies and/or immunotherapy are illustrated.

Surgery after sonidegib treatment achieves complete response in locally advanced basal cell carcinoma of the face.

Basal cell carcinoma accounts for 75% of skin cancers worldwide and is the most common malignancy in Caucasians. Since chronic ultraviolet exposure is the major risk factor for its development, sun-exposed areas such as the face are frequently affected. The gold-standard treatment is surgical excision. Radiotherapy may be considered in selected cases such as unresectable primary tumors. In some patients, when the risk of a significant functional/cosmetic deficit advises against both surgery and radiotherapy, target therapy (hedgehog pathway inhibitors) can be administered alone or in a neoadjuvant setting, to reduce the tumor size and make it eligible for surgery. Vismodegib as a neoadjuvant treatment before surgery has been investigated in a single, multicentre, open-label, phase II trial (VISMONEO); however, sonidegib has not yet been evaluated in this setting. We report the cases of two patients with locally advanced basal cell carcinoma of the face who achieved complete remission with sonidegib followed by a more limited surgical excision than would have been needed without target therapy.