Objectives: To investigate the frequency of a first therapy interruption (TI) > or = 12 weeks, to identify the factors associated with TI and with therapy resumption, and to compare the risk of developing clinical events during TI and during continuous therapy.
Methods: Observational study of 3142 patients who started a first highly active antiretroviral therapy (HAART) regimen. End points were time to (1) first TI of > or = 12 weeks, (2) subsequent therapy resumption, and (3) development of new AIDS-related events or death.
Results: Over a median follow-up period of 41 months (interquartile range: 18-60 months), 721 patients (22.9%) interrupted HAART for > or = 12 weeks, with a probability of 28.6% (95% confidence interval [CI]: 26.7-30.6) by 4 years from the date of therapy initiation. Patient decision (47.4%) and toxicity (24.0%) were the main reasons for TI. Women, injection drug users, and patients with a higher current CD4 cell count were more likely to interrupt. The median time to therapy resumption was 12 months (95% CI: 11-14). The higher the current CD4 count, the slower was the rate of resuming therapy; conversely, patients who stopped because of failure and those with a pre-HAART viral load >100,000 copies/mL resumed therapy sooner. Two hundred eighty-one patients experienced clinical progression at a rate of 2.6 per 100 person-years (pys) (95% CI: 2.3-3.0) while patients were on therapy and 3.5 per 100 pys (95% CI: 2.4-4.8) during TI. The adjusted relative hazard of clinical progression associated with TI was 2.75 (95% CI: 1.14-6.65; P = 0.03).
Conclusions: TI occurring in clinical practice is associated with an increased risk of clinical progression; hence, it should be discouraged outside strictly experimental settings.