Field-directed radiotherapy using volumetric modulated arc therapy (VMAT) is a promising new option for treating multiple actinic keratosis in elderly patients.
Associate Professor Chris Baker, from St Vincent’s Hospital Melbourne, told the Australasian College of Dermatology ASM that the limited effectiveness and durability of current treatments was disappointing for many patients with severe sun damage.
He said a recent comparison of four field-directed therapies, published in the NEJM, had highlighted the treatment gap.
The study found the probability of treatment success at 12 months was 74.7% with fluorouracil, 53.9% with imiquimod, 37.7% with photodynamic therapy and 28.9% with ingenol mebutate.
And participants in the Dutch study were likely to be an easier population to treat than Australian patients with their high tumour load, severe diffuse damage and frequent cutaneous horns.
Associate Professor Baker added that areas of significant field cancerisation with lots of actinic keratosis and scars from past excisions and grafts were a clinical conundrum.
“Basically these are patients who have generally severe field damage. Fluorouracil reduces the rate at which SCCs appear for 12 months but then that effect is lost. Topical therapies haven’t helped and there isn’t really a lot more to offer them.”
He said the ideal patient for field radiotherapy would be a patient in their 70s or 80s.
“The aim of the treatment is to cut down the rate at which cancers are appearing. It saves the patients morbidity and potentially mortality because this is an age group where if they get an SCC that gets away from them it can be serious, but also there is a quality of life issue.”
Dr Michael Guiney, a radiation oncologist from Genesis Care, told the meeting that VMAT could deliver targeted therapy to areas such as the scalp in bald men, the forearm and lower limb.
That included the flexibility to deliver higher doses to areas with biopsy provide skin cancers and lower doses to areas of actinic keratosis.
Once components like skullcaps, head casts and CT scans has been prepared, the actual duration of radiotherapy was only about 15 minutes.
He said follow-up results included good to excellent cosmesis with complete response in 86% of 57 evaluated fields. There had been no reports of new or recurrent invasive skin cancer.
Some patients were now out to three years follow-up – evidence of both dramatic and durable response.
Associate Professor Baker told the limbic treatment plans aimed for a balance between patient convenience and achieving the best results.
“The more frequently it is done and the lower dose, the less reaction and the better the result. Generally it’s about 20 treatments over a month.”
He added that clearing the ‘dreadful damage’ on the backs of hands and forearms of elderly patients could give them their life back.
Concerns about radiotherapy causing subsequent malignancies in the long term were played down given the advanced age of patients likely to be receiving VMAT.