Because of the introduction of HAART and chemoprophylaxis for opportunistic infections survival rates among HIV-infected population have been dramatically improved[9
]. However non-HIV-related causes of death have been increasingly reported in the recent past[2
]. Non-HIV causes may include but are not limited to various systemic diseases and non-AIDS defining malignancies[2
Colon cancer is one of the important malignancies among hematological and solid organ cancers reported in HIV infected individuals[13
]. Immunological, genetic and viral factors may play a vital role in the etio-pathogenesis of colon cancer in this population[52
]. Cancer of colon may present at an earlier age, advanced stage and more aggressively in HIV infected individuals[17
Prevalence of screening for colorectal cancer by endoscopic measures varies between 52% and 74% in different geographical areas of the United States[54
] among the average risk population. However, in our study, only 25% of the average-risk patients diagnosed with HIV underwent screening colonoscopy, which is far lower than national and state prevalence rates. There are no genders or ethnic differences between the patients who underwent screening colonoscopy when compared with patients who did not. Although mean age is slightly higher in those who underwent colonoscopy (58 years vs
56 years), the age range is wider (50-84 years) in the group that did not have screening, indicating lower prevalence of screening colonoscopy in older HIV population.
However, disease severity measured by viral load showed strong association with the rate of screening colonoscopy being done in HIV population. HIV patients who had screening colonoscopy had well-controlled disease compared with the other group. Viral suppression resulting from treatment adherence could explain higher compliance to screening colonoscopy. However it may not always be true as drug resistance mutations[56
] could enhance viral replication even in good treatment adherence cases.
Interestingly, we found higher polyp (55%) and adenoma (32%) detection rates in HIV population when compared with the average-risk population[59
]. The average adenoma detection rates reported in men and women of general population are 25% and 15%, respectively. However, in our study, adenoma detection rate is high in both genders with men (34%) and women (27%). These finding in accordance with the existing data on colon cancer in HIV individuals and strongly support aggressive screening in this particular group of population. However, the present guidelines stratify colon cancer risk based on family history and other variables and recommend colorectal cancer screening for average risk population starting at 50 years of age[30
]. HIV status of the individual is not considered in the present guidelines to stratify the risk of colon cancer and subjecting for screening[30
]. There is increased incidence of malignancies in immunosuppressive states even though colon cancer is rarely reported[52
]. The prognosis of HIV patients with malignancies depends on the extent of immune-suppression and mortality is higher for non-AIDS-defining malignancies[53
]. However, in our study, HIV patients with less severe immunosuppression are screened more frequently, leaving patients with severe immunosuppression without screening where mortality is high[62
At this point it is uncertain whether HIV or HAART medications are increasing the risk of non-AIDS-defining malignancies[14
]. However, there is definitely higher incidence of non AIDS defining malignancies in HIV population on HAART prompting timely screening and diagnosis[13
Our study lacks definitive advantages of prospective cohort or more refined randomized controlled studies. There was no matching between subjects in the study and control groups. As we collected data from old medical records, the accuracy of the information is not always perfect. However, the observations in our study, especially polyp and adenoma detection rates cannot be ignored. There were no cancers detected during screening colonoscopy in this group. We can explain this by the fact that patients might have undergone screening colonoscopy at an earlier stage of the disease process or it may be an incidental finding.
We conclude that there has been existing evidence showing early and aggressive presentation of colon cancer in HIV population. Our study provided further data on higher polyp and adenoma detection rate in HIV-infected population. Although further prospective studies are needed to have more refined results, we suggest that HIV-infection status may have to be considered while assessing colon cancer risk, and individuals with HIV infection should be considered at higher risk for colon cancer and screened accordingly. Currently there are no published guidelines on how to screen HIV infected population for colon cancer. However as suggested for other high risk patients it may be reasonable to screen HIV infected population starting at age 40, but further studies needed to evaluate and support this recommendation[65