WEDNESDAY, July 16 (HealthDay News) -- An unusual case involving a sudden remission of lung cancer highlights the carcinogenic potential of certain drugs used to treat Crohn's disease, experts say.

The patient, a 69-year-old female ex-smoker, developed lung cancer while being treated with anti-tumor necrosis factor (TNF) medications for her Crohn's disease.

However, the malignancy vanished after doctors stopped giving her the medications, British researchers report in the July 17 issue of the New England Journal of Medicine.

"There is an underlying concern about the use of these drugs and the possible increase of certain kinds of cancer," said Dr. Len Lichtenfeld, deputy chief medical officer of the American Cancer Society. "This report raises the awareness that doctors and patients have to have in using these drugs. We certainly need to be more vigilant about lung cancer in patients who get these treatments."

The rare case has broader implications and sheds light on the possible effect of anti-TNF medications -- which are also used to treat rheumatoid arthritis -- on patients' immune systems, the team say. This family of biologic drugs includes adalimumab (Humira), etanercept (Enbrel), and infliximab (Remicade).

One theory is that the woman, who had been a heavy smoker for 35 years, had had her lung cancer held at bay by her immune system. However, the anti-TNF drugs she was taking for her Crohn's may have weakened that system, allowing the lung cancer to emerge, the researchers say.

The woman's lung malignancy "was expected to be fatal within months," said co-author Jack Satsangi, a professor of gastroenterology at the University of Edinburgh in Scotland. "However, on stopping anti-TNF agents the cancer has completely regressed - and she is healthy more than two years later," he said.

The woman had been diagnosed with lung disease (not cancer) in 1999. In 2000, she was diagnosed with Crohn's disease, which was then treated with TNF medications -- first Remicade, then Humira. In 2006, she was diagnosed with lung cancer.

Her physicians discontinued treatment with Humira, but continued on methotrexate, which is from another class of drugs. The woman did not undergo surgery for her cancer or receive radiation or chemotherapy. In addition, no other biologic drugs were given to treat her lung cancer, the researchers report.

Even so, by April 2007 a scan of her lungs found no trace of the cancer.

"This is most remarkable, and adds to the concerns regarding the use of these agents, and we do not use these drugs in patients with heavy smoking histories," Satsangi said.

The association of TNF medications with lung cancer has been seen before, the authors note. The development of lung cancer among people taking these medications is particularly worrisome among ex-smokers. In fact, Satsangi's group has seen three such cases among people older than 65.

Satsangi's team believes that ex-smokers and people with a history of lung disease taking these medications should be carefully monitored, especially those aged 65 and older.

Lichtenfeld agreed that there have been concerns about the use of these drugs and the development of cancers, particularly lymphoma.

The new report implies that the woman's immune system was keeping the lung cancer in check, but that anti-TNF treatment interfered with her immune response, allowing the cancer to become evident, Lichtenfeld said. "[But] when the drug was withdrawn, the body's native mechanism was re-energized and was able to put this cancer into remission," he explained.

Whether this finding applies to all people taking anti-TNF medications isn't clear, Lichtenfeld added. "Will all patients who received this medication, when it is withdrawn, see their lung cancers go away? I don't think you can draw that conclusion from this report," he said.

"Unusual case reports have been a feature of medicine for a long time," Lichtenfeld said, and whether or not this report has implications for understanding and treating cancer generally remains uncertain. "However, I am sure this report will spark discussion about those questions," he said.

More information

There's more on biologic drugs at the American College of Rheumatology.