Kaposi Sarcoma (KS) is the most common AIDS-defining cancer. Typically patients respond well to standard combination antiretroviral therapy. However, cases of KS progression do occur in the context of HIV treatment and a suppressed viral load. When this arises additional chemotherapy is added to the patients treatment. This chemotherapy can achieve good responses but carries a risk of immune reconstitution inflammatory syndrome (IRIS), drug interactions and unpleasant side-effects. An alternative treatment option is therefore needed. Currently Interferon alfa is approved for the treatment of AIDS-related KS however little is known about the efficacy of the less toxic form- pegylated interferon (PegIFN). Researchers in Rotterdam therefore conducted a study with PegIFN in combination with antiretroviral therapy. The study included ten participants diagnosed with KS, on HIV therapy. Eight participants had an undetectable viral load at baseline. PegIFN therapy was given weekly as subcutaneous injections and duration was based on response. Results showed that a treatment response was observed in eight participants, who cleared KS and maintained their response to the time of last follow-up, a median of 645 days. Of the remaining participants one had a partial response with an improvement of cutaneous lesions but pulmonary lesions continued to progress. The last participant became critically ill and died. The study concluded that PegIFN could be an effective therapy for KS with minimal side effects.