Twenty-five years ago, a diagnosis of AIDS was a nearly immediate death sentence.
But now that patients with the AIDS virus are living longer, doctors are discovering a new set of complications: People with HIV have a much higher risk of developing certain cancers - lung, liver, head and neck, to name a few - and doctors fear that a cancer epidemic among this group could be coming.
Researchers in Maryland, home to one of the nation's largest AIDS populations per capita, are among the leaders in an effort to solve what has become something of a medical mystery.
"We're seeing people we have treated successfully for HIV at much higher risk" for cancer, said Dr. Kevin J. Cullen, director of the University of Maryland's Greenebaum Cancer Center. "The reasons aren't fully understood."
New research presented yesterday by a Johns Hopkins epidemiologist at a national cancer conference shows that patients with HIV are twice as likely as the general population to get any of the cancers not previously linked to the disease. Previous studies have put the risk of developing certain cancers as much as ten times higher for those with HIV.
There are some hypotheses for why this is so: HIV patients are simply living long enough to get cancer diagnoses; their immune systems are weakened by disease or injured by antiretroviral drugs; those with HIV are more likely to engage in high-risk behaviors. One prominent researcher wonders whether HIV drugs themselves could be a carcinogen.
What scientists learn about cancer and the immune system could have ramifications not just for those with HIV but also for everyone else.
"We're really at the first stages of systematically looking at the epidemic and fully looking at cancer," said Dr. William A. Blattner, an associate director of the University of Maryland's Institute of Human Virology. "Before, you died from AIDS, so you didn't have time to develop cancer. ... The unusual observation is the cancers are occurring at a much younger age."
Some of the most common cancers being seen among those with HIV are the ones known to be caused by viruses - such as anal and head and neck cancers, which have been linked to the human papillomavirus, and liver cancer, which has been linked to hepatitis.
One theory is that HIV depresses the immune system, allowing cancer-causing viruses to take hold.
Certain cancers have long been associated with HIV and AIDS. Kaposi's sarcoma, non-Hodgkins lymphoma and cervical cancer - all linked to viruses - were seen from the earliest days of the AIDS epidemic. It's the other cancers that are today being seen in much greater numbers, now that HIV in the United States has become a long-term, manageable condition not unlike diabetes.
"There's a real concern about all these cancers and what they portend," said Dr. Mark Wainberg, director of the McGill University AIDS Center in Montreal. "Obviously, we don't want to have an epidemic of cancers in long-term HIV-infected people."
Meredith Shiels, the author of the paper presented yesterday at the American Association for Cancer Research meeting in Prince George's County, said it's possible these cancers might have been seen sooner if antiretroviral drugs had come along years earlier. "Perhaps if they had lived longer, we would have seen this 10 years ago," said Shiels, a doctoral candidate at the Johns Hopkins Bloomberg School of Public Health.
In the 1980s and 1990s, Maryland's Cullen said, "virtually no one [with HIV] who developed cancer could survive rigorous cancer treatment." Antiretroviral drugs have made HIV patients stronger, he said.
Cullen told of a patient of his, a young woman with HIV who had healthy blood counts. When she got head and neck cancer, she was able to tolerate the full-bore treatment and appears to be rid of it. But then she developed pre-malignant lesions in her cervix and recently had to undergo a hysterectomy. She knows that even as she lives with HIV, she is at risk for further cancers. Doctors have found that cancer treatments sometimes don't work as well in immune-compromised people.
Some researchers have suggested that cancers are developing regularly in all of us but that the immune system is able to keep most of them in check. The immune system of a person with HIV might not be able to perform this function as well.
At the same time, HIV patients who get cancer don't always have the weakest immune systems, further confounding researchers.
Researchers at Hopkins and the National Cancer Institute, meanwhile, have been studying the elevated risk of lung cancer in patients with HIV.
In November 2003, Dr. Malcolm Brock, a Johns Hopkins thoracic surgeon, and others noticed that every week at the hospital, there seemed to be another HIV patient being diagnosed with lung cancer. "Finally, we said, 'Something is going on,' " he recalled last week at a conference on HIV and cancer at the University of Maryland School of Medicine.