1685PClinical course and therapeutic management of classical and endemic Kaposi’s Sarcoma (C/E KS)

Abstract Background KS is an HHV8 related lympho-angioproliferative disease with 4 clinical settings: post-transplant, epidemic, endemic, and classic. Although several studies described the clinical course of epidemic and post-transplant KS, the lack of large cohorts of C/E KS precluded such characterization. Our study aimed to describe the clinical course of C/E KS and identify risk factors for systemic treatment (ST) initiation and response. Methods We performed a retrospective study including 160C/E KS (n = 131 C and n = 29 E) patients diagnosed between 1990 and 2013 in 1 French dermato-oncology center). Results Median age was 62.6years [IQR:54.5;72.4] and Male/Female sex ratio was 140/20. During a median follow-up of 4.8years, 14% patients did not require any treatment while 44 and 41% required local and systemic treatments respectively. Among the 66 patients who required ST, 53% had more than one line of treatment. Cumulative incidence of ST initiation after 2years of follow-up was 28.4% [95%CI:20.5.35.5], and the median time from diagnosis to ST initiation was 8.8years [95%CI:4.7;12.7]. Instantaneous risk of ST initiation decreases over time. Multivariate analysis identified 3 risk factors for ST initiation: E versus C KS (HR: 4.19 [95%CI:2.32; 7.55]), total number of lesions higher than 10 (HR: 4.68 [95%CI:2.47;8.87]), and presence of edema (HR: 1.84 [95%CI:1.02;3.33]). Best overall response (BOR) after the first-line of treatment was CR in 14%, PR in 69%, SD in 8% and PD in 9% patients. Type of first-line therapy (low dose interferon, chemotherapy or other), type of KS (E or C), age at therapy initiation and time between diagnosis and ST initiation were not associated with BOR. Given the chronic evolution of KS and the impact of ST on the quality of life, we evaluated the treatment-free interval (TFI=time between end of first-line and start of second-line) during the first 2years after ST initiation. The mean TFI was 306days [95%CI:199;413] for interferon and 422days [95%CI:320;524] for chemotherapy treated patients. Conclusions Our study reveals important ST initiation risk factors in C/E KS. No major efficacy difference was observed between interferon and chemotherapy, thus enabling treatment choice based on patient’s fitness. Legal entity responsible for the study The authors. Funding Has not received any funding. Disclosure All authors have declared no conflicts of interest.