Concurrent HIV and cancer present special challenges in the clinic, regardless of which disease is diagnosed first. The simultaneous treatment of HIV and cancer is complicated by patients’ weakened immune systems, the lack of routine HIV screening, and interactions between drugs. Infectious disease specialists at MD Anderson routinely treat HIV in cancer patients and are discovering ways to overcome these challenges.
HIV and cancer
The relationship between HIV and cancer is not fully understood, but the virus is known to confer a high risk for various cancers.
“For many years, we had a group of cancers that were associated with HIV, the so-called AIDS-defining cancers: cervical cancer, Kaposi sarcoma, and non-Hodgkin lymphoma,” said Harrys Torres, M.D., an assistant professor of Infectious Diseases. “Now, with advances in HIV treatment, patients are living longer and developing non-AIDS-defining cancers.”
Compared with the general population, people with HIV have higher rates of lung cancer, melanoma, head and neck cancer, and anal cancer. “The immunocompromised state predisposes patients to the development of cancer, similar to what is seen in solid-organ–transplant patients,” said Bruno Granwehr, M.D., an associate professor of Infectious Diseases.
The high rates of cancer among HIV patients have a devastating consequence. “One-third of deaths among people with HIV in the United States are cancer-related,” Torres said. “That may have to do with the late diagnosis of HIV in patients whose cancer is diagnosed first and the limited approach to HIV screening at U.S. cancer centers.”
Screening cancer patients for HIV
Because many patients with both HIV and cancer are unaware that they have HIV, Torres and Granwehr believe that HIV screening should be included in the routine workup for cancer patients. Torres said, “Of the HIV-positive patients who come to MD Anderson for cancer care, 16%–33% don’t know they have HIV until they get tested here.”
Most large cancer hospitals, including MD Anderson, do not currently screen all patients for HIV, although MD Anderson patients with hematological malignancies typically are screened, as are those with other cancers who have HIV risk factors.
Granwehr said HIV screening in cancer patients is overlooked at cancer centers for numerous reasons, such as assumptions that patients were tested before referral for cancer treatment and confusion about the consent requirements for testing, which vary by state. In addition, older patients — the population most affected by cancer — often are not screened because of the misconception by some clinicians that HIV is an issue among young people only. However, Granwehr said, “With an increasingly healthy older population, there are more new cases of HIV in people over 50 years old; it’s one of the fastest growing populations of newly diagnosed HIV patients.”
Granwehr is leading a group that is working to improve the mechanics of HIV testing at MD Anderson. “We’ve proposed incorporating HIV testing in to our ‘front door’ consent form,” he said. This measure would facilitate HIV testing and reduce the number of patients in whom screening is overlooked.
Granwehr added, “If you’re going to use chemotherapy or other treatments that would further suppress a cancer patient’s immune system, you should know as far in advance as possible if a patient has HIV. This test should be considered as necessary at baseline as assessing liver or kidney function. It’s important to test cancer patients for HIV as part of their workup because patients can be treated for their cancer and their HIV simultaneously with success.”
Treating HIV in cancer patients
Studies of patients who have both HIV and cancer have shown that those who receive concurrent HIV treatment and cancer treatment survive longer than do those who receive cancer treatment only. For this reason, patients at MD Anderson with HIV are referred to the Infectious Disease Clinic. The infectious disease specialists work closely with oncologists to tailor each patient’s regimen of antiretroviral drugs for HIV treatment according to the patient’s cancer treatment.
“If a patient is receiving chemotherapy here and HIV treatment from an outside provider, we can work with that provider to modify the antiretroviral regimen if necessary,” Granwehr said.
According to Granwehr and Torres, the most important challenge of treating HIV in patients who are also undergoing cancer treatment is avoiding unwanted interactions between HIV drugs, chemo drugs and other agents commonly used in cancer patients (e.g., antifungals, antivirals, and immunosuppressants) and the resulting toxic effects.
Although physicians at MD Anderson have successfully treated hundreds of patients who have HIV and cancer, much remains unknown about the interactions between the antiretroviral drugs used in HIV treatment and the chemotherapy drugs and targeted agents used in cancer treatment.
To address this gap in knowledge, Torres and his colleagues conducted a retrospective analysis of 154 patients who were treated for HIV and cancer and followed up regularly at MD Anderson. The researchers analyzed rates of adverse events, side effects, clinically relevant drug interactions, and efficacy in patients treated with various antiretroviral drug regimens.
Among the commonly used classes of HIV drugs, integrase strand-transfer inhibitors (INSTIs) were tolerated best by cancer patients in the study and had the fewest interactions with cancer drugs, although non-nucleoside reverse transcriptase inhibitors (NNRTIs) also were well tolerated with few drug interactions (see figure). INSTI- and NNRTI-based regimens had similar efficacy rates. HIV protease inhibitors were shown to have clinically significant interactions with several cancer drugs, and regimens based on protease inhibitors were less efficacious than INSTI and NNRTI-based regimens.
Torres said that without INSTIs, it would be much more challenging to treat HIV in cancer patients. “INSTIs have virtually zero interactions with immunotherapeutic agents and other anticancer drugs,” agreed Granwehr, a co-investigator in the retrospective analysis.
If toxic effects due to drug interactions or other causes necessitate treatment changes for a patient with HIV and cancer, the antiretroviral regimen typically is adjusted rather than the anticancer regimen. According to Torres and Granwehr, the cancer treatment is rarely modified, although in a very few cases, the dose of a chemo agent is adjusted.
Granwehr added that the timing of cancer treatment is seldom affected by HIV treatment, although if a patient newly diagnosed with HIV has just begun treatment for the virus, surgery for cancer might be postponed to make sure the patient is stable. Otherwise, HIV treatment rarely interferes with surgery or radiation therapy for cancer.
Another challenge of treating HIV in cancer patients is monitoring the patients’ progress. “The two markers typically used to monitor HIV are viral load and CD4 cell count,” Torres said. “But the CD4 cell count can be affected by cancer medications, so HIV in cancer patients is best monitored by viral load.”
Improving detection and treatment
Despite the successful treatment of many patients with HIV and cancer, there are no standardized guidelines for HIV treatment in cancer patients. In the report of their retrospective study, Torres and his co-authors urged a prospective study to further the development of such guidelines.
In addition, Granwehr said he hopes more cancer centers will recognize the importance of screening cancer patients for HIV. “Cancer patients who are tested and treated for HIV tolerate their cancer therapy and their HIV therapy very well. Oncologists should not be hesitant to test patients for HIV for fear that their patients might not benefit from cancer treatment.”
For more information, contact Dr. Bruno Granwehr at 713-745-8631 or Dr. Harrys Torres at 713-792-6503.
This story originally appeared in the February 2015 issue of Oncolog.