THURSDAY, Jan. 10, 2008 (HealthDay News) -- Women who are struck by a rare lung disease could find their tumors shrink by 50 percent with the help of the transplant drug sirolimus, a new study suggests.
The Cincinnati researchers who made the discovery also demonstrated the drug might improve lung function in some patients over time.
Lymphangioleiomyomatosis (LAM), a disease that exclusively targets women, is characterized by progressive loss of lung function due to the invasion of abnormal muscle tissue that obstructs airways. In its early stages, LAM can be confused with emphysema because of its effects on breathing. People with LAM often need oxygen treatments and lung transplants as the disease continues its course. According to the American Lung Association, as many as 250,000 women worldwide might have the disease.
The new treatment was also effective in reducing tumors in patients suffering from tuberous sclerosis complex (TSC), a rare genetic multi-system disease.
The two diseases share a genetic mutation that affects the activation of the enzyme mTOR, which is responsible for controlling the growth and spread of cells. Sirolimus, a drug that is usually prescribed to prevent the rejection of transplanted organs, also prevents mTOR activity, according to the researchers. Sirolimus is also known as rapamycin (Rapamune).
Publishing in the Jan. 10 edition of the New England Journal of Medicine, the researchers concluded that sirolimus has the potential to help patients with either disease avoid surgery for the tumor angiomyolipomata, common to both conditions.
"Less invasive therapies are clearly needed to treat the angiomyolipomata that people with TSC and LAM develop, and a drug that maintains or shrinks tumor size may reduce the need for procedures such as surgery," study author Dr. John Bissler, a physician/scientist in the division of nephrology and hypertension at Cincinnati Children's Hospital, said in a prepared statement. "Our data suggest that mTOR inhibition with sirolimus may hold promise for treating these and other disease manifestations in patients with TSC and LAM."
Bissler and his colleagues treated 20 patients who had angiomyolipomata tumors with sirolimus for 12 months. They reported that, at the end of the year, the tumors shrank by about half. Eleven of the patients who had LAM and took sirolimus for the year also showed a 10 percent to 15 percent improvement in expiratory air flow, a standard measure of lung function.
The researchers followed up with 18 of the original patients after a year without the sirolimus treatment. They found that tumor size had increased to about 85 percent of original pre-treatment size.
Tumors in five of the original patients, though, were 30 percent smaller than their original size after a year without the medication. The study authors theorized that this could be a result of apoptosis, a kind of programmed cell death.
After a year without treatment, the patients' lung function declined but was still better than what could be expected from similar patients after two years without any intervention, the researchers said. The improved lung function could be because of the lessening of obstructions and trapped gas in the lungs, the researchers noted.
Patients reported side effects from the sirolimus treatment that included mouth sores, diarrhea, upper respiratory infections and joint pain.
The researchers acknowledged that the small study needs further follow-up. A phase III clinical trial of the drug as a treatment for LAM patients is planned, they said.
To learn more about LAM, visit the American Lung Association.