Basal cell carcinoma

Introduction

Cutaneous basal cell carcinoma (BCC) is a common malignancy arising in the basal cells of the epidermis and its appendages. It is locally invasive and very rarely gives rise to metastatic disease.
BCC usually presents as a slowly developing indurated area or nodular tumour that may ulcerate. Occasionally lesions can only be confidently differentiated from other non-melanoma and melanoma skin cancers on histoogy.
Alliance protocols are based on BAD guidelines 2021, NICE guidance on management of low-risk BCCs in the community, and US NCCN guidelines, alongside regional experience, expertise and patterns of care.
An RSH OMFS post-operative algorithm for BCC has previously been prepared.

The BAD guidelines incorporate NICE and NCCN perspectives into criteria assigning BCCs into high risk and low risk.
These criteria are somewhat complex and challenging to process in primary care or in the MDM setting.
In general terms, clinically low risk BCCs are small (pT1) tumours with well defined borders, not recurrent, present on most of the trunk and extremities, and lower risk parts of the face. Clinically high risk BCCs are larger, or on 'mask' areas of the face (central face, eyebrows, periorbital nose, lips, chin, mandible, preauricular, postauricular, temple, ears) and higher risk areas of the body (genital areas, hands, nail units, ankles and feet).
Advanced BCC is defined by BAD as either (a) metastatic or (b) locally advanced with one or more high risk factors, in which standard treatment modalities are considered potentially contraindicated by tumour or patient factors.

The following types of case should be referred to secondary care.

Clinically high risk BCC.
Clinically low risk BCC in the absence of a recognised GPwER, or if the primary care facility is not suitable for surgery.

The standard approach is excision biopsy or standard surgical excision with curative intent. Incisional/ punch/ curette or shave biopsy of the lesion may be performed as appropriate where the clinical diagnosis is not clear, particularly where reconstructive surgery may be needed post excision with curative intent.
Low risk BCC should be excised with a target clinical margin of 4 mm.
Primary BCC with a high risk factor should be excised by at least 5 mm with immediate reconstruction if the BCC has well-defined clinical margins under bright lighting and magnification or dermoscopy.
High risk BCC with poorly defined clinical margins, or recurrent BCC with one other high-risk factor, should be excised with delayed reconstruction, or Mohs micrographic surgery.
There should be adequate excision at the deep margin to a clear plane, including a fat layer where present.
Wider and deeper excision should be considered where the clinical diameter is 2 cm or more.
Mohs micrographic surgery should additionally be considered in the following circumstances
1. Recurrent BCC with at least one other high risk factor, especially if the tumour is at a high risk site
2. Advanced BCC
Surgical excision is an option for certain patients with advanced BCC.

Radiotherapy is a treatment option for adults, typically above the age of 60, with low and high risk BCC. It should be discussed as an option for most patients. The clinical oncologist will on request provide the likely radiotherapy schedule and side effects to the primary clinician to inform an initial discussion with the patient, leading to formal referral to the oncology clinic for further discussion +/- treatment if required.
Radiation margins will vary by histology, extended in infiltrative histology.
Radiotherapy can be considered for patients with excised BCC with involved margins, although a significant proportion of these patients will not experience local recurrence. There is no indication for fully excised BCC, notwithstanding the presence of any high risk factors, with treatment reserved for any recurrence.
Radiotherapy should not be offered where the lesion is:
1. recurrent following previous radiotherapy;
2. associated with certain genetic syndromes predisposing to skin cancers, and/or subject to heightened radiation sensitivit, for example Gorlin syndrome or xeroderma pigmentosum;
Radiotherapy is typically disfavoured where the lesion is:
1. on areas of poor blood supply, for example the lower limbs;
2. in a younger patient in whom late effects, including second cancers, may be a long term risk;
3. involving bone or cartilage.

For low risk BCC in patients who are unsuitable for or decline standard surgical excision, topical imiquimod, topical 5-FU, cryosurgery or topical PDT are alternative options.
An observational approach is also highly supportable in asymptomatic low risk BCC where the risks of treatment may outweigh the benefits, particularly in frail elderly patients.

Pathology departments will adhere to guidelines on specimen handling and reporting as described in the Royal College of Pathology Minimum Data Set (MDS) for basal cell carcinoma.
RSH clinicians are encouraged to use a dedicated form for submission of samples to histopathology.

BCCs should be discussed at the SSMDT in the following circumstances.
1. Complex management cases including advanced or metastatic BCC.
2. Close (< 1mm) or involved margin excision.
3. Patients who may benefit from Mohs micrographic surgery.
Some cases will require imaging studies, which will generally follow the principles of imaging in cSCC.

Some patients may choose not to have definitive treatment. They can be counselled that the risk of significant progression is at least 25% over 2-5 years.
Patients with an involved margin after primary surgery may be considered for surgical re-excision, Mohs surgery or radiotherapy.
Patients with adequately treated BCC are not routinely followed up, unless there is a history of multiple BCCs or other skin cancers.
82% of local recurrences occur within five years. 36% of patients develop new primary BCCs. 20% of high risk patients (skin type and UV exposure) develop multiple new lesions. Furthermore, following a BCC, there is an increased risk of developing other skin cancers. Patents should be counselled about self-examination and reporting, UV exposure, and potential chemoprotective effects of nicotinamide.

Vismodegib was made available to patients with advanced BCC, unable to receive surgery or radoitherapy, via the Cancer Drugs Fund in 2013. Approximately 10 patients were treatment in the Alliance. Responses were mixed, with some showing complete and durable responses beyond treatment discontinuation, and others developing resistance from approximately six months. Local experience was consistent with literature reports that vismodegib did not usefully downstage BCCs to facilitate reduced surgical defects, as 'islands' of tumour often remain after apparent regression.
Vismodegib was removed from the CDF in 2017 due to high cost and lack of cost effectiveness.
It was reinstated via a clinical commissioning policy in July 2021 for adults with Gorlin syndrome or non-Gorlin syndrome-related BCCs who have a minimum of six lesions and no spread to other sites in the body. It is advised to be used on an intermittent dosing schedule to improve tolerability. Vismodegib is highly teratogenic and SmPC guidance on contraception and pregnancy testing should be followed.

Pembrolizumab is active in basal cell carcinoma, with a response rate of approximately 30%.