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Session 13 Oral Abstract Session Antiretroviral Chemotherapy: Combination Therapy, Drug Resistance, and Treatment Interruption Session Time: Tuesday, 10 am - 12:30 pm Room 4B

11:45   48. Interruption/Stopping Antiretroviral Therapy and the Risk of Clinical Disease: Results from the EuroSIDA Study. J. D. Lundgren*, S. Vella, L. Paddam, A. Blaxhult, N. Vetter, N. Clumeck, G. Panos, M. Fisher, C. Katlama, and A. N. Phillips EuroSIDA Coord Office, Hvidovre, Denmark Background: Reports suggest that it has been relatively common for people to interrupt (or stop altogether) antiretroviral therapy. Methods: We studied 3610 people within the EuroSIDA study who started a HAART regimen (3 drugs taken simultaneously). We assessed the tendency for therapy interruption and evaluated the relative hazard of a new AIDS-defining event (ADE) or death associated with therapy interruption/stopping using a Cox model. To minimize bias caused by stopping induced by terminal disease we assessed the risk associated with interruption for at least 3 months. Results: At start of HAART median CD4 count was 214 /mm3, median viral load 25,000 copies/mL, 6% had a previous AIDS diagnosis. There was a total 7328 person-years (median 3.2 years) after start of HAART. 565 (16%) interrupted HAART. Median (IQR) CD4 count at interruption and nadir were 242 and 130/mm3, respectively. Median (IQR) viral load at interruption was 3000 copies/mL (<400-45,000). 274 of the 565 (49%) have so far since restarted therapy. 290 developed a new ADE or died, incidence rate: 0.04 per person-year. 28 of these events occurred after being off therapy for at least 3 months (28/140 person-years = 0.20 per person-year). After adjustment for demographic variables and previous ADE before HAART the relative hazard of new ADE/death associated with having been off therapy for at least the past 3 months was 6.0 (95% CI 4.0-8.9; p=0.0001). This changed to 2.4 (95% CI 1.6-3.6; p=0.0001) after adjustment for the latest CD4 count and viral load (known within at most the past 3 months). In those interrupting there were 25 clinical events in 48 person-years (0.52 per person-years) in people with latest CD4 count < 200 /mm3 compared with 3 clinical events in 92 person-year (0.03 per person years) in people with latest CD4 count > 200/mm3. When 6 months was used instead of 3 months as a lag-time the adjusted relative hazard was unchanged at 2.4. Further, consistent results were obtained when we considered the relative hazard associated with therapy interruption (i.e. people subsequently restarted therapy). Conclusions: These data indicate that risk of AIDS and death increases several-fold upon therapy interruption/stopping. The absolute risk remains closely linked to the latest CD4 count and was higher among patients with a latest CD4 count below 200/mm3.

©2002 9th Conference on Retroviruses and Opportunistic Infections