Ingenol mebutate in the treatment of 'Hydroxyurea-induced Squamous Dysplasia': a single centre experience

'Hydroxyurea-induced Squamous Dysplasia' (HISD) is a cutaneous side-effect related to chronic oral treatment with Hydroxyurea. Ingenol mebutate gel is a topical drug approved for the treatment of multiple, non-hypertrophic actinic keratoses (AK) localized within a limited cancerization field. Since HISD may be considered as a drug-induced variant of classic AK, ingenol mebutate is likely to have therapeutic effects.

The aim of this study was to evaluate efficacy and safety of ingenol mebutate 150 mcg/g and 500 mcg/g, as a treatment of HISD lesions on face/scalp and trunk/extremities respectively.

Seven areas with a mean of lesions of 5.9 ± 1.7 in five patients with HISD were treated. Patients with lesions on face/scalp self-treated a 25 cm(2) skin affected area with ingenol mebutate gel 150 mcg/g, one tube daily for 3 days. Patients with lesions localized on trunk/extremities treated the same size affected area with ingenol mebutate gel 500 mcg/g, one tube daily for 2 days. Clinical assessment and count of HISD lesions has been performed by an experienced dermatologist at day 0, at day 57, and at time of last feasible follow-up visit (median 337 days). Safety assessment included the report of all SAEs.

At 57-day follow-up, we observed an overall response rate (ORR) - the sum of Complete Responses (CR) + Partial Responses (PR) - of 87.5%, with a 57.1% CR, and a 78.0% total lesions' reduction compared to time 0 (P < 0.01). On a median follow-up of 337 days, we observed a long-term ORR of 71.4%, a 57.1% CR ratio and a 65.9% total lesions' reduction compared to time 0 (P = 0.01). No severe (grade 3-4) adverse events have been reported.

Although obtained in a small case series, these encouraging data lead us to propose ingenol mebutate gel as a possible treatment for HISD.