Malignant pleural mesothelioma is incurable except in rare cases when the tumor can be completely removed surgically.

The phase II study of 29 patients at St. Bartholomew''s Hospital in London offers the first look at the effects of vinorelbine on mesothelioma, which affects about 2,000 to 3,000 new patients a year in the United States.

The results surprised the researchers: a partial tumor response in seven patients (24%), stabilization in 16 (55%), and disease progression in six patients (21%).

Previously published studies of other single chemotherapy agents show a response rate ranging from 7% to 20%. Combination therapy can achieve greater gains but has a higher toxicity.

"The study shows that this drug has the potential to be helpful and with relatively good tolerance; but I wouldn''t say this is a breakthrough yet," says Franco Muggia, MD, director of medical oncology at New York University School of Medicine. "It may be a building block for other treatments to be developed."

Vinorelbine''s eventual role against mesothelioma depends on a few factors, Muggia says: how long patients remain in remission; whether larger studies achieve the encouraging 24% response rate; and how well it combines with other chemotherapy drugs.

Malignant pleural mesothelioma is a cancer that develops in the thin, slippery membrane between the lung and chest wall. Growth of the cancer can turn the membranes into a thick, rubbery straitjacket, depriving the lung of its ability to expand.

As important as vinorelbine''s effect on tumors was the rarity of serious side effects, says lead author Jeremy P. Steele, MD, Department of Medical Oncology, St. Bartholmew?s Hospital. All patients reported some degree of fatigue, but no one experienced significant hair loss, vomiting, nausea, or appetite loss. Almost two-thirds of patients had low white blood cell counts at some time during their treatments. Although low white blood cell counts reduce patients? resistance to infection, only one patient in this study had an infection serious enough to require treatment in a hospital. In addition to shrinkage of tumors observed by computed tomography scans, many patients noted improvement in symptoms.

Among patients who completed between one and two six-treatment cycles of vinorelbine, a dozen (52%) reported improved lung-related symptoms and 15 (65%) reported improvement in other physical symptoms. Moreover, many patients began feeling better within a month, exceeding the study team''s expectations.

St. Bartholomew''s, a nearly 900-year-old hospital in the center of London, sees 120 new patients with mesothelioma a year, roughly 10% of the United Kingdom''s cases. The disease is on the rise in Europe and tends to surface about 40 years after asbestos exposure, Steele says, commonly striking former asbestos manufacturing plant workers, and those in the building and shipping trades.

Muggia, an editor of the American Cancer Society''s patient information materials on mesothelioma, says that more research needs to be done to prove vinorelbine is lending substantial benefit to quality or length of life. Phase II studies, by design, are small and preliminary, and they need to be confirmed by larger groups, he says.

Those plans are in place. The UK''s Medical Research Council and British Thoracic Society will undertake a three-pronged, randomized phase III trial comparing vinorelbine against two approaches: a combination of mitomycin, vinblastine and cisplatin; and pain control alone.

"This is not a cure for this cancer, unfortunately," Steele says. "But it''s as good as anything around that we''ve seen, with as low or lower side effects."