Recognizing Unusual Tumors Part 1: Defining and Managing High-risk Basal Cell and Cutaneous Squamous Cell Carcinoma

Dr. Suneel Chilukuri and Dr. Neil A. Swanson

Basal Cell Carcinoma

Despite the fact that treatment for basal cell carcinoma (BCC) is curative in the vast majority of cases, some patients are at high risk of recurrence and, in a few patients, lesions can progress to a point where local therapy is not possible and the prognosis is quite poor (Puig, 2015).

Characteristics of High-risk Disease

Treatment decisions in patients with BCC are usually made on the basis of estimated risk for recurrence. Aggressive, infiltrating tumors are frequently ulcerated and have ill-defined margins; ulcerated BCC is usually larger than non-ulcerated tumors and may be locally destructive. Risk associated with tumor size varies with location and is defined as >6 mm for the mask area, >1 cm for the cheek, forehead, scalp, and neck, and >2 cm in other body areas. Histological subtype should also be considered in assessing risk for relapse. Morpheaform, sclerosing, infiltrating, desmoplastic, micronodular, basosquamous, keratotic, and metatypical subtypes are associated with higher risk vs superficial and the nodular forms of BCC. Perineural invasion is also associated with a higher risk of relapse; but vascular invasion does not appear influence long-term outcomes.  Importantly, more than 30% of BCCs have mixed pathology, combining less and more aggressive subtypes (e.g., nodular BCC with areas of infiltrating BCC) (Marzuka, 2015; Puig, 2015; Proceddu, 2015).

There is no agreement on the prognostic significance of other factors, such as a previous history of radiotherapy, in patients with BCC.

Squamous Cell Carcinoma

Cutaneous squamous cell carcinoma (cSCC) represents 20% of all non-melanoma skin cancer, and has the ability to metastasize to any organ in the body. It is estimated that cSCC is diagnosed at a rate of 15-35 per 100,000 people and this is expected to increase 2-4 % per year (Burton, 2016).

Risk and Staging cSCC

Although most sSCC are easily cured, there is a high-risk subset with an increased risk of metastasis and death (Karia, 2014). Factors believed to be associated with higher risk cSCC include location on the ear, lip, or genitalia; poorly differentiated, acantholytic desmoplastic, or adenoid squamous histology; perineural invasion; and clinical features that include rapid growth, pain, paresthesias, invasion to bone, and cranial nerve involvement.

Despite identification of individual factors associated with higher risk cSCC, there is no consensus definition of high-risk disease and there is limited published information on best approaches to treatment.  At present, these high-risk patients are typically managed with a multidisciplinary approach decided on a case-by-case based on tumor board discussions. Several clinical and histologic risk factors are associated with increased risk of recurrence, metastasis, and death in patients with cSCC, but high-risk cSCC has not been consistently defined, nor has associated prognosis been estimated (Karia, 2014).  There are multiple staging systems for SCC, including those from the American Joint Committee on Cancer (AJCC)/Union for International Cancer Control (UICC) and a more recently developed system developed at the Brigham and Women’s Hospital (BWH) (Jambusaria-Pahlajani, 2013; Karia, 2014). A comparison of these systems indicated that current UICC and AJCC tumor (T) staging fail to identify high-risk sSCC because the majority of poor outcomes occur in low T stages and heterogeneous tumors with diverse risk profiles. Conversely, the BWH system has four statistically distinct stages and enhanced ability to appropriately upstage high-risk tumors from low to high stages (Karia, 2014).

Interventions in cSCC and BCC

Retinoids for Prevention Treatment of Skin Cancer

Systemic retinoids have been shown to be effective for the prevention of skin cancer (Tilley, 2015); and initiation of prophylaxis is indicated to prevent morbidity from multiple primary tumors and to decrease the risk of death from high-risk tumors.  Candidates for retinoid administration include patients with xeroderma pigmentosum, basal cell nevus syndrome, or severe sun damage; and patients who are immunosuppressed for solid organ transplantation or with chronic lymphocytic leukemia (Reilly, 2004).

Smoothened Inhibitors in the Treatment of BCC and Risk for cSCC

The smoothened inhibitors, vismodegib and sonidegib, have been shown to be highly effective for the treatment of patients with advanced BCC (e.g., Sekulic, 2012; Migden, 2015); and many new agents from this class (e.g., saridegib, CUR61414, BMS-833923, LEQ506, PF-04449913, TAK-441) are in development for the treatment of BCC and other cancers. However, extensive use of vismodegib in patients with BCC has been associated with increased risk for the development of cSCC.  Case reports have described emergence of new-onset keratoacanthomas and cSCCs in patients with advanced BCCs during vismodegib therapy (Aasi, 2013; Orouji, 2014); and results from a recent case-control study carried out at the Stanford Medical Center which included 180 patients indicated that treatment of BCC with vismodegib was associated with a >6-fold increase in the risk for cSCC (Mohan, 2016).  The mechanism(s) underlying this phenomenon are not understood, but it has been suggested that smoothened inhibition may inadvertently activate the RAS/MAPK pathway, thereby promoting tumorigenesis (Zhao, 2015).

References

Aasi S, Silkiss R, Tang JY, et al. New onset of keratoacanthomas after vismodegib treatment for locally advanced basal cell carcinomas: a report of 2 cases. JAMA Dermatol. 2013;149:242-243.

Burton KA, Ashack KA, Khachemoune A. Cutaneous squamous cell carcinoma: a review of high-risk and metastatic disease. Am J Clin Dermatol. 2016 Jun 29. [Epub ahead of print].

Jambusaria-Pahlajani A, Kanetsky PA, Karia PS, et al. Evaluation of AJCC tumor staging for cutaneous squamous cell carcinoma and a proposed alternative tumor staging system. JAMA Dermatol. 2013;149:402-410.

Karia PS, Jambusaria-Pahlajani A, Harrington DP, Murphy GF, Qureshi AA, Schmults CD. Evaluation of American Joint Committee on Cancer, International Union Against Cancer, and Brigham and Women’s Hospital tumor staging for cutaneous squamous cell carcinoma. J Clin Oncol. 2014;32:327-334.

Marzuka AG, Book SE. Basal cell carcinoma: pathogenesis, epidemiology, clinical features, diagnosis, histopathology, and management. Yale J Biol Med. 2015;88:167-179.

Migden MR, Guminski A, Gutzmer R, et al. Treatment with two different doses of sonidegib in patients with locally advanced or metastatic basal cell carcinoma (BOLT): a multicentre, randomised, double-blind phase 2 trial. Lancet Oncol. 2015;16:716-728.

Mohan SV, Chang J, Li S, Henry AS, Wood DJ, Chang AL. Increased risk of cutaneous squamous cell carcinoma after vismodegib therapy for basal cell carcinoma. JAMA Dermatol. 2016;152:527-532.

Orouji A, Goerdt S, Utikal J, Leverkus M. Multiple highly and moderately differentiated squamous cell carcinomas of the skin during vismodegib treatment of inoperable basal cell carcinomas. Br J Dermatol. 2014;171:431-433.

Porceddu SV. Prognostic factors and the role of adjuvant radiation therapy in non-melanoma skin cancer of the head and neck. Am Soc Clin Oncol Educ Book. 2015:e513-518.

Puig S, Berrocal A. Management of high-risk and advanced basal cell carcinoma. Clin Transl Oncol. 2015;17:497-503.

Reilly P, DiGiovanna JJ. Retinoid chemoprevention in high-risk skin cancer patients. Dermatol Nurs. 2004;16:117-120, 123-126; quiz 127.

Sekulic A, Migden MR, Oro AE, et al Efficacy and safety of vismodegib in advanced basal-cell carcinoma. N Engl J Med. 2012;366:2171-2179.

Zhao X, Ponomaryov T, Ornell KJ, et al. RAS/MAPK activation drives resistance to Smo inhibition, metastasis, and tumor evolution in Shh pathway-dependent tumors. Cancer Res. 2015;75:3623-3635.