Abstract P6-12-24: Risk and predictors of psoriasis in breast cancer patients: A Swedish population based cohort study
Authors: Yang H , Brand JS , Li J , Ludvigsson JF , Ugalde-Morales E , Chiesa F , Hall P , Czene K 
Published: February 2018

Abstract
Background The risk of psoriasis in breast cancer patients is largely unknown, as available evidence is limited to case findings. We systematically examined the incidence and risk factors of psoriasis in breast cancer patients.
Methods Using Cox regression models, a Swedish nationwide cohort of 56,235 breast cancer patients (2001-2012) was compared to 280,854 age-matched reference individuals from the general population to estimate the incidence and hazard ratio (HR) of psoriasis. We also calculated HRs for psoriasis according to treatment, genetic and lifestyle factors in a regional cohort of 8,987 patients.
Results In the nationwide cohort, 599 breast cancer patients were diagnosed with psoriasis during 307,684 person-years (median: 5.1 years) compared to 2,795 cases in the matched individuals during 1,666,038 person-years. Breast cancer patients were at an increased risk of psoriasis (HR=1.17; 95% CI=1.07-1.28) and its most common subtype (psoriasis vulgaris; HR=1.33; 95% CI =1.17-1.52). The risk of psoriasis vulgaris was long-term increased up to 12 years after diagnosis. Treatment specific analyses indicated an increased risk of psoriasis in patients treated with radiotherapy (HR=2.44; 95% CI=1.44-4.12) and mastectomy (HR=1.54, 95% CI=1.03-2.31). Apart from treatment-specific effects, we identified genetic predisposition, obesity and smoking as independent risk factors for psoriasis in breast cancer patients.
Table 1. Hazard ratios for psoriasis according to treatment characteristics HR (95% CI) Total No.No. of CasesModel 1Model 2Endocrine therapy No1533271.00 (REF)1.00 (REF)Yes71001210.90 (0.59-1.36)0.80 (0.52-1.24)Chemotherapy No55441021.00 (REF)1.00 (REF)Yes3070460.82 (0.57-1.19)0.70 (0.47-1.04)Radiotherapy No2061231.00 (REF)1.00 (REF)Yes65741251.78 (1.14-2.78)2.44 (1.44-4.12)Surgery Lumpectomy5203941.00 (REF)1.00 (REF)Mastectomy3459550.96 (0.69-1.34)1.54 (1.03-2.31)Model 1: adjusted for age and calendar period of breast cancer diagnosis. Model 2: model 1 plus all the treatment factors.
Table 2. Hazard ratios of psoriasis according to genetic and life style factors HR (95% CI) Total No.No. of casesModel 1Model 2PRS score Tertile 11440131.00 (REF)1.00 (REF)Tertile 21442362.74 (1.45-5.17)2.83 (1.50-5.34)Tertile 31483402.94 (1.57-5.49)2.98 (1.59-5.58)BMI &lt;25 kg/m22331401.00 (REF)1.00 (REF)25-30 kg/m21434281.18 (0.73-1.92)1.15 (0.71-1.87)&gt;30 kg/m2536192.29 (1.32-3.98)2.10 (1.20-3.68)Physical activity per week 0 hours762211.00 (REF)1.00 (REF)0-2 hours1645360.77 (0.45-1.33)0.77 (0.44-1.32)&gt;2 hours1910300.56 (0.32-0.98)0.59 (0.33-1.03)Regular smoker No1773261.00 (REF)1.00 (REF)Yes2546621.65 (1.04-2.61)1.59 (1.00-2.52)Genetic predisposition for psoriasis was defined by a polygenic risk score (PRS) including 35 SNPs for psoriasis susceptibility. Model 1: adjusted for age and calendar period of breast cancer diagnosis. Model 2: all of the risk factors were put into the model, including treatment.
Conclusions The incidence of psoriasis is elevated among breast cancer patients, with treatment, lifestyle and genetic factors defining the individual risk profile. Our findings underline the complex etiology of psoriasis in breast cancer patients and may help to assess individual risk of psoriasis after a breast cancer diagnosis.
Citation Format: Yang H, Brand JS, Li J, Ludvigsson JF, Ugalde-Morales E, Chiesa F, Hall P, Czene K. Risk and predictors of psoriasis in breast cancer patients: A Swedish population based cohort study [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P6-12-24.