Antiretroviral therapy has been shown to increase survival and delay progression to AIDS in HIV-positive patients. Population-based studies have shown that HAART (which includes two nucleoside reverse transcriptase inhibitors with either a non-nucleoside reverse transcriptase inhibitor or one or two protease inhibitors) decreases the incidence of KS as an AIDS-defining diagnosis.83-85 In a multicentre cohort of 30 000 patients from centres in the US the incidence of KS fell from 4-8 per 100 person-years in 1990 to 1-5 per 100 person-years in

1997 during 54 000 person-years of follow up between 1990 and 1997.85 The relative risk of developing KS was 0-41 (95% CI 0-2-0-8) for patients on triple antiretroviral therapy.

Reconstitution of the immune system following treatment with HAART may also affect established KS and prolong time to disease progression. Small uncontrolled studies and case reports have documented reduction of KS lesions after initiation of HAART.86-88

One small RCT of 37 evaluable patients with a high risk of developing AIDS-related KS (CD4 count >200 cells x 106/litre, no "B" symptoms and no history of opportunistic infections) randomised patients to 4-hourly treatment with one of the following: oral placebo, oral zidovudine, 250 mg, intravenous zidovudine, 0-5 mg/kg, or intravenous zidovudine, 2-5 mg/kg.80 At 6 weeks, four of nine patients receiving oral placebo and 10 of 28 patients receiving oral or intravenous zidovudine had progressive KS. After 12 weeks, only five patients receiving zidovudine had a minor response (defined as the absence of new KS lesions and a 25-50% regression in at least 25% of existing lesions). In this study zidovudine was not an effective treatment for KS in terms of response rate or delay of progression. However, the number of patients in each of the four treatment arms was small, and monotherapy with zidovudine has been superseded by HAART as standard therapy in the treatment of HIV infection.

A small prospective cohort study of 39 patients with AIDS-related KS commenced on HAART found that 10 of 19 patients, who received no other systemic therapy for KS, achieved a complete response by ACTG criteria.81 Patients were more likely to respond if their CD4 count was >150 cells x 106/litre. A retrospective cohort study identified 101 patients who received local or systemic therapy for KS and were subsequently commenced on HAART.82

What are the effects of antiretrovirals in the treatment of AIDS-related Kaposi's sarcoma?

Thirty-three patients were excluded because new anti-KS therapy was instituted at the same time as commencement of HAART. For the remaining 78 patients, the median time to treatment failure before starting HAART was 0-5 years (defined as the time between the final and penultimate anti-KS therapy before HAART). After the start of HAART, median time to treatment failure was 1-7 years (defined as time between start of HAART and next anti-KS therapy).82 No correlation was demonstrated between CD4 count response and control of KS but a statistically significant correlation between progression of KS and virological failure of HAART (defined as viral load >5000 copies/ml) was found. However, five of 24 patients (21%) on HAART did not have virological failure (viral load <200 copies/ml) at the time of KS progression. Immune reconstitution has been postulated as the mechanism of response of KS to antiretroviral therapy but response to HAART and the relationship to CD4 count response is unpredictable.

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