Old Radiotherapy techniques with dose to entire nose.

Dr Jeremy Croker, Radiation Oncologist, Wembley

ED: Smart technology is making doctors look good and leaving patients more comfortable when it comes to radiotherapy for skin cancers.

Non-melanomatous skin cancer affects at least 2% of the population, with an increasing incidence because of our aging population and longer life expectancy. Many patients require repeat procedures for skin cancer. Surgery, topical treatments, photodynamic therapy and radiotherapy all play an important role. Recent advances in accuracy and delivery of radiotherapy and the increasing use of Volumetric Modulated Arc Therapy (VMAT) now provides further options for patients, particularly in difficult anatomic areas.

Efforts are underway to establish if these new radiotherapy techniques can treat the difficult problems of wide-field cancerisation and widespread in situ disease.

Extent of the problem

Non-melanomatous skin cancers (NMSCs) comprise primarily squamous cell carcinomas (SCC) and basal cell carcinomas (BCC). They are the most common cancer in people with fair skin and Australia has the highest incidence in the world. Risk factors include age, fair skin, male gender, chronic sun exposure and immunosuppression.

New VMAT technique limiting dose to internal structures.

Common anatomic regions for NMSCs are sun-exposed areas of the head and neck, along with the extremities – sometimes challenging areas to treat in terms of cosmesis and wound healing. Once an individual develops a NMSC, there is a significant risk of developing a second NMSC (the three-year risk for BCC and SCC is 44% and 18%, respectively).

Field cancerisation refers to the problem whereby large areas of skin have altered tissue, ranging from dysplastic through in situ to invasive carcinoma. It is within these regions that patients may develop multiple cancers over time.

New VMAT technique – scalp minimising dose to brain

Where radiotherapy fits in

Surgery remains a mainstay of treatment, and radiotherapy has been a useful therapeutic option for 120 years. Radiotherapy has an approximate 90% local control rate at five years. In the past decade, advances in computing have fuelled parallel advances in imaging technologies, radiotherapy planning and delivery and treatments can now be delivered with sub-millimetre accuracy.

There is more confidence and certainty now about delivering a tumouricidal radiation dose to the target whilst sparing adjacent critical organs and normal structures. Moreover, the advent of VMAT permits dose to be sculptured around curved surfaces, enabling complex topographical shapes such the scalp, nose and legs to be treated, whilst sparing internal structures such as the brain, nasal septum and lymphatics (see Images).

As well as excellent control rates, radiotherapy is non-invasive making it easy to administer in a population with multiple co-morbidities or contraindications to surgery or anaesthetics.

Radiotherapy for skin cancer is generally well tolerated with a usual limited side effect profile that can include alopecia, pigmentary changes, telangiectasias, fibrosis and atrophy. The rare more serious side effects are generally limited to larger dose per fraction treatments and include soft tissue or bone necrosis, cataracts, conjunctival scarring and eyelid deformity. In a large 2017 review, 90% of patients self-reported good or excellent aesthetic outcomes following skin radiotherapy.

Early published outcomes for using VMAT radiotherapy for both invasive disease and field cancerisation is encouraging but robust data remains sparse at present.

There is a need to collect prospective data and to this end, GenesisCare, along with dermatologists throughout Australia have developed a National Dermatology & Radiation Oncology Registry with the aim of prospectively collecting local control, acute and late toxicity data, along with patient satisfaction outcomes. As the data matures it is hoped that in a carefully selected population, radiotherapy will offer increasing benefit in patients with skin cancer.

References available on request

Author competing interests: No relevant disclosures.

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