INTRODUCTION
Psoriasis is a lifelong, relapsing, immune-mediated disease that affects the skin and is present in an estimated 125 million people worldwide.1-5 Plaque psoriasis manifests as sharply demarcated, scaling, and erythematous lesions that can be painful and severely pruritic.2,6,7 The strong psychological impact of this disease can substantially decrease a patient’s quality of life.2,7,8
Because there is no cure for psoriasis, treatment strategies aim to clear active disease sites and prolong symptom-free periods.9 Topical vitamin D analogs (eg, calcipotriene) and corticosteroids (eg, betamethasone) are cornerstones of treatment for patients with mild to moderate psoriasis.9-13 Calcipotriene and betamethasone dipropionate (Cal/BD) foam is a fixed combination of calcipotriene at 50 mcg/g and betamethasone dipropionate at 0.64 mg/g. Cal/BD foam is an FDA-approved treatment for plaque psoriasis in patients 12 years of age and older.10 The efficacy of Cal/BD foam has previously been demonstrated in a population of patients with disease ranging from mild to severe disease in 1 Phase 2 trial and in 2 Phase 3 trials.11,14,15
Although most patients (~80%) have mild-to-moderate disease,12 an overwhelming number of studies are performed in populations with moderate-to-severe psoriasis.16 The skewing of study samples toward moderate-to-severe psoriasis populations may partly be a consequence of the tools that are used in clinical trials. For example, for the Investigator’s Global Assessment (IGA) of disease severity, treatment success is defined as a score of “clear" (IGA=0) or “almost clear†(IGA=1) for patients with moderate-to-severe disease, but patients with mild disease are required to be fully clear of visible disease (IGA=0).11 Thus, patients with moderate (IGA=3) or severe (IGA=4) baseline IGA scores have less stringent requirements and more potential to achieve an IGA score that is sufficiently reduced to fulfill criteria for treatment success. In contrast, patients with mild baseline disease (IGA=2) have less room for improvement and are required to be completely clear
Because there is no cure for psoriasis, treatment strategies aim to clear active disease sites and prolong symptom-free periods.9 Topical vitamin D analogs (eg, calcipotriene) and corticosteroids (eg, betamethasone) are cornerstones of treatment for patients with mild to moderate psoriasis.9-13 Calcipotriene and betamethasone dipropionate (Cal/BD) foam is a fixed combination of calcipotriene at 50 mcg/g and betamethasone dipropionate at 0.64 mg/g. Cal/BD foam is an FDA-approved treatment for plaque psoriasis in patients 12 years of age and older.10 The efficacy of Cal/BD foam has previously been demonstrated in a population of patients with disease ranging from mild to severe disease in 1 Phase 2 trial and in 2 Phase 3 trials.11,14,15
Although most patients (~80%) have mild-to-moderate disease,12 an overwhelming number of studies are performed in populations with moderate-to-severe psoriasis.16 The skewing of study samples toward moderate-to-severe psoriasis populations may partly be a consequence of the tools that are used in clinical trials. For example, for the Investigator’s Global Assessment (IGA) of disease severity, treatment success is defined as a score of “clear" (IGA=0) or “almost clear†(IGA=1) for patients with moderate-to-severe disease, but patients with mild disease are required to be fully clear of visible disease (IGA=0).11 Thus, patients with moderate (IGA=3) or severe (IGA=4) baseline IGA scores have less stringent requirements and more potential to achieve an IGA score that is sufficiently reduced to fulfill criteria for treatment success. In contrast, patients with mild baseline disease (IGA=2) have less room for improvement and are required to be completely clear
