Acitretin chemoprophylaxis

Mechanism

Acitretin is a second-generation aromatic retinoid — a synthetic vitamin-A derivative that binds retinoic acid receptors (RAR α/β/γ) and modulates keratinocyte proliferation, differentiation, apoptosis and immune-modulatory gene expression. The chemopreventive effect appears to derive from:

• Reduced keratinocyte hyperproliferation and dysplasia.
• Apoptosis of pre-malignant keratinocytes.
• Anti-inflammatory and immunomodulatory effects.
• Reduction in the actinic-keratosis burden and field-change progression.

The effect is suppressive rather than curative — pre-malignant lesions return rapidly after discontinuation (“rebound”).

Indications

• Trial Solid organ transplant recipients (OTRs) with a high cSCC burden — typically ≥ 2 new cSCCs per year, recurrent or aggressive cSCC, or accelerating field change despite optimal skin-directed therapy.
• Xeroderma pigmentosum — chemoprevention of UV-induced keratinocyte cancers.
• Basal cell naevus syndrome (Gorlin) — reduction of new BCC formation, particularly in patients unsuitable for hedgehog inhibitor.
• Selected non-OTR patients with very high actinic damage and multiple cSCCs (e.g. chronic immunosuppression, lung transplant recipients on voriconazole, idiopathic field change).
• Severe disorders of keratinisation are a non-oncology indication.

Contraindications

• Pregnancy or planning pregnancy (absolute) — severe teratogen.
• Childbearing potential without highly effective contraception + a Pregnancy Prevention Programme equivalent process.
• Severe hepatic impairment.
• Severe renal impairment.
• Concomitant tetracyclines (raised intracranial pressure risk).
• Concomitant methotrexate (additive hepatotoxicity).
• Vitamin A supplements (additive toxicity).
• Significant unmanaged hyperlipidaemia (relative).

Dosing and titration

Initiation

• Start low: 10 mg orally once daily with food.
• Titrate up over 2–4 weeks based on tolerance.

Maintenance

• Target 0.2–0.5 mg/kg/day — typically 20–30 mg orally once daily for an average adult.
• If tolerated and effective, may titrate up to 0.75 mg/kg/day in resistant cases (uncommon).
• Doses < 0.2 mg/kg/day are often subtherapeutic for chemoprevention; doses > 0.5 mg/kg/day have a sharply higher mucocutaneous adverse-event rate without clear additional benefit.

Duration

• Continue indefinitely while benefit persists and tolerated — the chemopreventive effect is lost rapidly on cessation (rebound within weeks).
• If stopping, consider a gradual taper over 4–6 weeks and increased surveillance for the following 6 months.

Quick reference

Acitretin is available as 10 mg and 25 mg capsules in the UK. Round dose to a convenient multiple; once-daily dosing improves adherence. Take with food (improves absorption and reduces nausea).

Adverse events

Mucocutaneous (commonest, dose-related, reversible)

• Cheilitis (essentially universal at therapeutic dose).
• Xerosis, pruritus, fragility of the skin.
• Diffuse alopecia (10–30%); usually reverses on dose reduction.
• Nail dystrophy and periungual granulation; paronychia.
• Sticky-skin sensation.
• Photosensitivity.

Metabolic

• Hyperlipidaemia — raised triglycerides > cholesterol; very common. May require statin or fibrate; if severe (TG > 8.5 mmol/L), reduce or stop.
• Hepatic transaminitis — usually mild and reversible.

Other

• Headache; rare benign intracranial hypertension (especially with tetracyclines).
• Mood / depression; rare reports of suicidal ideation — counsel and screen at follow-up.
• Myalgia, arthralgia; rare bony changes (diffuse idiopathic skeletal hyperostosis, DISH) with long-term use; premature epiphyseal closure in children.
• Reduced night vision; xerophthalmia.

Reproductive

• Severe teratogenicity: avoid pregnancy throughout treatment and for 3 years after the last dose (acitretin re-esterifies to long-half-life etretinate, especially with alcohol consumption).
• Alcohol can convert acitretin back to etretinate — counsel to avoid alcohol in women of childbearing potential.
• No clinically significant teratogenic risk via semen has been demonstrated; UK SmPC does not impose a male-partner contraception restriction. Blood donation is contraindicated during treatment and for 3 years after the last dose. Check current prescribing information.

Monitoring schedule

Baseline

• Full blood count, urea & electrolytes, liver function tests, fasting lipids (cholesterol, triglycerides), bone profile.
• Pregnancy test in childbearing potential (negative within 2 weeks of starting).
• Documentation of contraception plan; written counselling about teratogenicity.
• Baseline eye examination if pre-existing visual symptoms.

During treatment

• LFTs and fasting lipids: at 2–4 weeks after starting, then 4–6 weeks after each dose change, then 3-monthly when stable.
• Pregnancy test: monthly / every 28 days while on treatment in childbearing potential; after stopping, repeat pregnancy testing at 1–3 monthly intervals for 3 years after the last dose per UK SmPC / Pregnancy Prevention Programme (acitretin re-esterifies to long-half-life etretinate).
• Annual review of mood, joint symptoms, vision.
• Continuing skin cancer surveillance per the underlying indication.

Evidence summary

• Trial Bavinck 1995, J Clin Oncol: double-blind RCT in 38 renal transplant recipients with prior skin cancer; acitretin 30 mg/day for 6 months. New cutaneous SCC: 2 of 19 on acitretin vs 9 of 19 on placebo (P = 0.01). Foundational trial.
• Trial de Sevaux 2003: low-dose (0.4 mg/kg/day) vs high-dose acitretin in OTRs; similar efficacy, better tolerability at low dose.
• Consensus Systematic reviews (Chen 2005; Kadakia 2012) support consistent benefit while on treatment with rebound on discontinuation.
• Mechanistic note: the chemopreventive effect is dose- and time-dependent and lost rapidly on cessation; long-term sustained therapy is the typical strategy.

Practical pearls

• Initiate via a UK consultant dermatologist familiar with retinoid prescribing; in OTRs coordinate with the transplant team.
• Counsel about cheilitis at the outset and prescribe an emollient lip balm prophylactically.
• Set the expectation that some benefit appears within 3 months but full skin cancer reduction takes 6–12 months.
• Lipid management is part of the prescription — encourage Mediterranean-style diet, weight optimisation, alcohol moderation; statin or fibrate as needed.
• Have a pre-emptive plan for the rebound phenomenon if discontinuation is anticipated — taper, intensify surveillance, consider field therapy.
• Acitretin can be combined with topical 5-FU, imiquimod and MAL-PDT for field disease.
• Other chemoprevention options in OTRs: HPV vaccination, nicotinamide 500 mg twice daily (ONTRAC evidence in non-OTRs), mTOR inhibitor conversion (sirolimus / everolimus), and minimising voriconazole.