What is the prevalence of Kaposi sarcoma (KS)?

Updated: Apr 11, 2019
  • Author: Jessica Katz, MD, PhD, FACP; Chief Editor: Edwin Choy, MD, PhD  more...
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United States

Before the AIDS epidemic, Kaposi sarcoma was rare. Between 1975 and 1980, only 19 cases occurred in men aged 20-54 years, according to Surveillance, Epidemiology, and End Results (SEER) data (0.1 cases per 100,000). In 1981, an aggressive form of Kaposi sarcoma began to appear among men who have sex with men (MSM) as one of the harbingers of the AIDS epidemic. [37] At the beginning of the AIDS epidemic, just before 1980, 40-50% of MSM with AIDS developed Kaposi sarcoma. This phenomenon spurred research into the possibility of an infectious etiology. [58]  

The rate in all SEER areas increased from in the late 1970s to 17.5 per 100,000 in the late 1980s and then decreased to 2.2 per 100,000 as of 1999-2000. [59] In the United States, the risk of Kaposi sarcoma in sexually active MSM is much greater than in others infected with HIV. [60] The incidence of Kaposi sarcoma reached its zenith in 1989 among white men aged 20-54 years when it was the most common AIDS-associated neoplasm. Its incidence has dramatically declined since then.

In the mid 1990s, approximately 1 in 4 MSM contracted the disease. This number has decreased precipitously with the advent of safer sexual practices in the early 1990s and accelerated with the introduction of highly active antiretroviral therapy (HAART) in the mid 1990s. [60, 61] The dramatic decrease supports the hypothesis of the need for severe immunosuppression for the presumed sexual transmission of an infective agent such as Kaposi sarcoma–associated herpesvirus/human herpes virus 8(KSHV/HHV-8). [31]  

The decrease in HIV-related Kaposi sarcoma was most profound in men in the San Francisco area, from 7.9 to 1.6 cases per 100,000. [59] The incidence in other HIV risk groups initially was 10% in intravenous drug abusers, 4% in hemophiliacs, and 3% in children with AIDS. [62] It has decreased in these groups as well to a relatively steady rate of 2%, which is now the same rate for MSM. The disease may be contracted by other groups with HIV, such as women and heterosexual men, through unprotected sex. Overall, there has been a historic tendency to underreport Kaposi sarcoma in the AIDS population. [63]

The other major group in the United States in whom Kaposi sarcoma occurs is the posttransplant population, in whom the incidence is about 1 in 200. [64]

Currently, approximately 2,000 cases of Kaposi sarcoma, or about 6 cases per million population, occur yearly in the United States. [64] Historically, the incidence in African-American men peaked somewhat later than in white men, in 1991-1999. It was first noted in Hispanic men in 1992 when its incidence was transiently higher than in African Americans or whites. The dramatic drop in incidence has been seen in all major ethnic groups from 1992-2001, with stabilization since then. Currently, the highest rate is seen in African-American men, with a rate of 3 per 100,000, as opposed to rates less than 3 per 100,000 in decreasing incidence for Hispanics, whites, and Asians/Pacific Islanders, respectively.

As noted above, the incidence and severity of Kaposi sarcoma has lessened following the introduction of HAART. This reduction has been attributed to restoration of the immune system caused by these drugs. The regression occurs in parallel with increases in CD4 counts, usually within no more than 9-12 months. Conversely, progression occurs with increasing viral load, low CD4 counts, and opportunistic infection . [65]

Maurer et al, however, reported a cluster of cutaneous, refractory HIV-associated Kaposi sarcoma in patients in the San Francisco area with CD4 counts above 300 cells/μL and suppressed viral loads below 300 copies for at least 2 years. [66] All patients presented between November, 2004 and November, 2006 and were being treated with a protease inhibitor (PI) or non–nucleoside reverse transcriptase inhibitors (NNRTIs). None had a history of opportunistic infection. All the courses were indolent. These authors proposed that these cases are the result of aging in persons infected with both HIV and HHV8.

In a cohort study of 86,620 HIV-infected and 196,987 uninfected adults from 1996–2009, the cumulative incidence by age 75 for Kaposi sarcoma was 4.4% but dropped to 4.1% in the most recent period analyzed (2005–2009). [67]  

The specific HAART regimen may be important, as the drugs may also act as antitumor or antiangiogenic agents; for example, PIs may inhibit Kaposi sarcoma. [68]  However, a systematic review found that HAART significantly reduced the risk of incident Kaposi sarcoma regardless of the antiretroviral drug class used, even after adjusting for CD4 count. The CD4-adjusted incidence of Kaposi sarcoma decreased by approximately 50%, with either NNRTI-based- or PI-based HAART. [69]

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