Is it routine to have more than 12 sessions of Psoralen (PUVA) and Ultraviolet A (UVA) therapy for psoriasis?

PUVA Therapy in Psoriasis: Duration and Number of Sessions

It is medically acceptable to exceed 12 sessions of PUVA therapy for psoriasis, with guidelines recommending up to 150-200 total lifetime treatments as the maximum safe limit to minimize long-term skin cancer risk. 1

Standard Treatment Course and Efficacy

• PUVA therapy typically requires 20-25 treatments for a single course to achieve clearance of psoriasis 1
• In randomized controlled trials, 86% of patients achieved 75% improvement in PASI score (PASI-75) after 12 weeks of therapy 1
• A standard course of PUVA is typically 30-40 treatments 1
• PUVA achieves clearance in more patients with fewer treatment sessions than narrowband UVB (NB-UVB) and results in longer remission periods 2

Treatment Frequency and Protocol

• Treatment is typically administered 2-3 times per week 1, 3
• Research shows that twice-weekly PUVA can be as effective as thrice-weekly regimens while reducing cumulative UVA exposure 3
• Initial doses are based on either:
  • Minimal phototoxic dose (MPD) testing (starting at 50-70% of MPD)
  • Fitzpatrick skin type (fixed starting dose)
• Dose increments are typically 20-40% initially, decreasing to 5-10% as treatment progresses 4

Treatment Duration Considerations

Maximum Recommended Lifetime Exposure

• British Association of Dermatologists guidelines recommend limiting total PUVA exposure to 150-200 treatments lifetime 1
• American Academy of Dermatology guidelines suggest clinicians should try to minimize the number of PUVA treatments to decrease long-term skin cancer risk 1
• For patients with vitiligo (which has more stringent limits than psoriasis), an arbitrary limit of 150 treatments is advised for skin types I-III 1

Skin Cancer Risk Factors

• High cumulative UVA dose (>2000 J/cm²) or >200 treatments significantly increases squamous cell carcinoma (SCC) risk 1
• Risk is particularly elevated in:
  • Caucasians with skin types I-III
  • Patients with previous skin cancer history
  • Those previously treated with cyclosporine
  • Patients with previous exposure to ionizing radiation or arsenic 1

Maintenance vs. Intermittent Therapy

• After clearance, some patients may benefit from maintenance therapy (1-2 sessions monthly) 1
• However, there is no consensus on the need for maintenance PUVA regimens 1
• Many dermatologists prefer intermittent courses with treatment-free intervals to reduce cumulative exposure 1

Risk Mitigation Strategies

• Annual skin examinations for patients who have received >150 PUVA treatments 1
• Combination therapy with retinoids or vitamin D analogs to reduce the number of PUVA sessions needed 1
• Shielding of high-risk areas (genitalia, face) during treatment 1
• Consideration of rotational therapy with other modalities to limit cumulative PUVA exposure 1

Common Pitfalls to Avoid

1. Exceeding safe lifetime limits: Track cumulative treatments across all courses of therapy
2. Inadequate monitoring: Regular skin examinations are essential for patients with high cumulative exposure
3. Inappropriate dose increments: Patients with skin types I-II require smaller increments to avoid erythema 4
4. Concurrent use with cyclosporine: This combination significantly accelerates skin cancer development 1
5. Failure to consider alternatives: NB-UVB may be preferable for certain patients, especially those with guttate or thin plaque psoriasis 5

In conclusion, while exceeding 12 PUVA sessions is routine and medically necessary for most patients with psoriasis to achieve clearance, the total lifetime exposure should be carefully monitored and limited to minimize long-term carcinogenic risk.