Change in pattern of secondary malignancies following Kaposi's sarcoma in the era of anti-retroviral therapy
Poster Feb 15, 2017
Fahad Mukhtar, Mmadili Ilozumba, Luu Hung
Background/Introduction: Studies have shown that people who develop Kaposi’s sarcoma (KS) are at higher risk of developing other malignancies. [1, 2] The demographics of people affected with KS has changed with KS occurring more frequently now in younger adults compared to elderly.  The demographics of people with HIV/AIDS has also changed.  Thirdly, antiretroviral agents now provide longer survival of people with HIV/AIDS and consequently people with KS. It is therefore very likely that the tumors associated with KS have also changed.
This study hypothesis is that the secondary cancers that develop in patients with KS have changed. We will study this hypothesis by calculating standardized incidence ratios for the secondary cancers using the Surveillance, Epidemiologic and End-Result (SEER) Program data from 1980-2013.
The SEER data from 9 registries was used to identify cases of KS diagnosed from 1980-2013. The primary outcome was development of secondary tumors in those with KS. Patients with KS were followed up to the date they developed a second tumor, date of death, date of last follow up or end of study period. Secondary cancers were considered only if diagnosed 2 months after a diagnosis of KS. Standardized incidence ratios and their 95% confidence interval were calculated for development of new secondary tumors. Analysis was stratified based on year of diagnosis comprising of Pre-HAART era (1980-1995) and HAART-era (1996-2013). Stratified analysis was then performed on a subset of the cases diagnosed from 1996-2013 by stratifying on: 1) Age of diagnosis into those less than 65 years and those older than 65 years to represent those with AIDS related KS and classical KS respectively; 2) Follow up period between KS and development of secondary tumor comprising of 1 year, 2-5 years, 5-10 years and >10 years; 3) Registries with higher rates of HIV/AIDS versus registries with lower rates of HIV/AIDS. Cases that were diagnosed during autopsy or from death certificate were excluded.
From 1980 to 1996, cancer of the rectum, anus, liver, cervix, Hodgkin’s Lymphoma (HL) and non-Hodgkin’s Lymphoma (NHL) had an SIR (95%CI) of 2.01 (1.00-3.60), 49.70 (33.53-70.94), 4.98 (2.79-8.22), 13.70 (2.82-40.03), 6.40 (2.76-12.60) and 48.97 (44.85-53.36) respectively. From 1996 to 2013, anal cancer, HL, NHL and liver cancer continued to occur higher than expected in people with KS (Table 2) with the addition of cancer of the tongue (SIR=6.99, 95% CI; 3.20-13.27), penis (10.28, 95% CI=1.24-37.13) and acute lymphocytic leukemia (ALL) (SIR=17.62, 95% CI=3.63-51.49). The SIR of developing any tumor after KS decreased from 3.36 to 1.94 from Pre-HAART to HAART era respectively.
Among cases of KS diagnosed from 1996 to 2013, 267 developed secondary tumors. People with KS who were less than 65 years and from high HIV/AIDS regions had significantly higher incidence of secondary tumors including tumors of the tongue, anus, liver, penis, NHL, HL and ALL. Individuals older than 65 years had a 2.54 fold increase incidence of developing NHL. Cases from low HIV/AIDS area had a 15 fold increase incidence of NHL and 59 fold increase incidence of anal cancer. When the analysis was stratified by follow up period, tumor incidence was highest in the period one to ten years after the diagnosis of KS for all the secondary tumors analyzed except for NHL which had a higher incidence within the first year following a diagnosis of KS.
There has been a significant decline in the overall risk of secondary tumors following Kaposi’s sarcoma. Tumors including acute lymphocytic leukemia, tumor of the tongue and penile tumor are increasingly becoming more common in the HAART era compared to the pre-HAART era. The excess risk for colon cancer and cervical cancer following KS in the pre-HAART era has now decreased significantly in the HAART era perhaps because of improved screening for these cancers which can be identified during pre-cancerous stage and treated accordingly. Similar to Biggar et al study , this study found that the excess risk for secondary tumor was highest among individuals less than 65 years, individuals from high HIV/AIDS region and during 1 to 10 years following a diagnosis of Kaposi’s Sarcoma. Close monitoring and screening for these secondary tumors is desirable in this category of patients with KS.