Changing incidence of Kaposi's sarcoma and non-Hodgkin's lymphoma among young men in San Francisco

A recent report from Australia indicated that population-based incidence rates of AIDS-related Kaposi's sarcoma (KS) and non-Hodgkin's lymphoma (NHL) have decreased substantially with the dissemination of highly active antiretroviral therapy (HAART), and that rates of KS have declined more quickly than those of NHL, so that NHL is now the most common AIDS-related cancer among individuals with HIV [1]. Previous studies of AIDS-related cancer trends [2–7] have shown that large and representative study populations [1,8,9] are needed to detect changes in the incidence of AIDS-related cancers. We utilized population-based cancer surveillance data to examine incidence trends of KS and NHL among men aged 24–59 years living in the city of San Francisco, a population with a long-standing history of elevated HIV seroprevalence. Yearly incidence rates of KS (International Classification of Diseases – Oncology, 2nd edition histology code 9140) and NHL (histology codes 9590–9595 or 9670–9717) were calculated and age-adjusted to the 1970 US standard population using SEER*Stat software [10]. These cancer surveillance data show that incidence patterns of KS and NHL have undergone tremendous changes among young men in San Francisco over the past 25 years, and that recent changes generally mirror those observed in Australia. Fig. 1 shows yearly incidence rates for KS and NHL from 1973 to 1998, the most recent year for which data are available. Notwithstanding incidence increases of 2000% for KS and 800% for NHL between 1982 and 1990, age-adjusted rates of both malignancies have recently dropped to levels similar to those recorded in the early 1980s, at the onset of the HIV epidemic. Particularly substantial declines have occurred between 1995 and 1998, with 87 and 73% decreases in the rates of KS and NHL, respectively. These declines are largely attributable to the dissemination of HAART among HIV-infected individuals in this population, although rate decreases do pre-date the availability of HAART, particularly for KS. As well as documenting a decrease in absolute magnitude, these data also confirm a recent change in the relative magnitude of KS and NHL rates. In 1997, for the first time since the beginning of the HIV epidemic, NHL rates among young men in San Francisco exceeded those for KS, with rates of NHL [38.5 cases per 100 000, 95% confidence interval (CI) 30.9–47.7] significantly higher than those for KS (27.0 cases per 100 000, 95% CI 21.0–31.7). Rates for 1998 showed a similar relationship (NHL rate 20.7 cases per 100 000, 95% CI 15.3–27.8; KS rate 14.7 cases per 100 000, 95% CI 10.4–20.5).Fig. 1.: Yearly incidence rates for Kaposi's sarcoma and non-Hodgkin's lymphoma from 1973 to 1998. ––▴–– Non-Hodgkin's lymphoma; ––•–– Kaposi's sarcoma.The introduction of HAART has greatly reduced the excess cancer morbidity and mortality experienced by HIV-infected individuals in San Francisco county. Like the Australian report, these data suggest a growing importance of NHL as an AIDS-related illness. NHL represents an increasing proportion of all AIDS-related complications reported to the San Francisco AIDS surveillance unit [11], and despite HAART, is rapidly fatal in the majority of individuals in whom it develops [12]. Unlike KS, the etiology of AIDS-related NHL remains poorly understood, and epidemiological and clinical characteristics of the disease in individuals diagnosed in the age of HAART do not differ substantially from those in individuals diagnosed before the introduction of HAART [12]. Although the short-term risks of NHL are probably reduced in individuals treated with HAART [1,8,9], the long-term risks remain uncertain, and previous studies have associated increased risks with prolonged immunodeficiency [13]. Although the dissemination of HAART has played a major role in reducing the cancer burden among individuals with HIV, we should continue to monitor closely the incidence of NHL and other cancers in populations with long-term survivors of HIV infection. Christina A.