Prognosis

The risk of progression of AKs to invasive squamous cell carcinoma (SCC) has been calculated to be between 0.025% and 16% per year.​[126][127] In older adults with a history of multiple keratinocyte carcinomas, risk of progression is 0.60% at 1 year and 2.57% at 4 years.[128]

The calculated lifetime risk of malignant transformation for a patient with AKs followed up for 10 years is between 6.1% and 10.2%.

Although spontaneous regression has been reported to be as high as 25.9% of AKs over a 12-month period, 15% subsequently reappear.[2]​​[53][129]

Misdiagnosis can also affect the outcome. One study showed that 36% of lesions previously diagnosed clinically as AKs were in fact SCC, and 14% of them were SCC in situ.[130] In another study, 4% of AKs clinically diagnosed by board-certified dermatologists were in fact SCC, and 5% were considered occult early stage of cutaneous malignancy.[131]

In addition, one study showed that 40% of all SCCs developed from clinically normal skin in the prior year, and 60% of SCC arose from previous AKs.[126]

It is estimated that 95% of SCCs on the lip develop from a preexisting actinic cheilitis lesion, and metastasis rate for SCCs on the lip are four times higher than cutaneous squamous cell carcinomas (cSCCs).[116]

Outcome in high-risk people (e.g., immunocompromised)

The risk of developing new AKs is even higher in immunocompromised people (e.g., transplant patients), in whom AKs have an increased malignant transformation rate.[132][133][134][135]

The cumulative incidence of developing skin cancer increases from 7% after 1 year of immunosuppression to 45% after 11 years, and 70% after 20 years.[136]

Patients with genetic melanin deficiency (e.g., albinism) and DNA instability (e.g., xeroderma pigmentosum) tend to develop AKs early in life, with 91% incidence in people with albinism >20 years old, and 19% in xeroderma pigmentosum patients.

Treatment outcomes

Treatment options often result in undesirable transient adverse effects, but they obtain high efficacy rates.[12]

Prevention with adequate broad-spectrum sunscreen has been found to decrease the number of AKs and prevent the development of new lesions.[44]

The usual cure rate of most of the treatments is >90%, with cryotherapy reported to produce 99% clearance.[137][138]

Cosmetic outcomes have been reported as good to excellent in 94% to 97% of complete response lesions.[139][140] There is a complete response (or cure) of 83% for freeze times >20 seconds.

Curettage with or without electrodesiccation has been reported to produce high cure rates, and good cosmetic results have been described.[137]

The overall efficacy for superficial peels has been calculated to be around 75%, with recurrence rates of 25% to 35%.[141]

One 2022 study described the 4-year risk of developing cSCC in patients previously treated with 5% fluorouracil, 5% imiquimod, or methyl aminolevulinate photodynamic therapy (PDT).[142]​ The overall risk was 3.7%, ranging from 2.2% in those treated with fluorouracil to 5.8% in those treated with imiquimod.

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