Summary: A new study finds that the antibiotic doxycycline can treat a certain type of lymphoma that starts in the eye. The discovery could simplify treatment for patients and help researchers understand what causes this cancer. The study, by researchers from Italy's San Raffaele H Scientific Institute, appears in the Journal of the National Cancer Institute.

Why it's important: Although eye lymphomas aren't common, they can be troubling to patients. The tumors are usually small often pea-sized but they can interfere with vision and often need treatment with radiation or even chemotherapy. Both kinds of treatment have side effects. Radiation can damage the eye and cause vision loss. Chemotherapy is a poor alternative because the drugs affect the whole body, even though the problem is a small tumor in the eye. Finding a simpler treatment with fewer side effects would be a great benefit to patients.

What's already known: Eye lymphomas belong to a class called MALT lymphomas. The most common MALT lymphoma starts in the stomach. In the past few years scientists have learned that MALT lymphomas of the stomach are associated with an infection by a bacterium called Helicobacter pylori. It turns out that treating the H. pylori infection with potent antibiotic combinations will not only eliminate the H. pylori, but also cause the lymphoma to regress. This has made antibiotics the standard treatment for MALT lymphomas of the stomach and many patients have been cured without using radiation or chemotherapy.

Eye lymphomas that start in the lids or tissue covering the eye (called conjunctiva) are also of the MALT type, leading investigators to suspect bacterial infection as their cause as well. They discovered that many eye lymphomas are associated with an infection with a bacterium called Chlamydia psittaci. The authors of the present study looked to see if antibiotic treatment of this infection would cause the lymphoma to regress.

How this study was done: Twenty-seven patients with eye lymphoma were enrolled in the study. Fifteen were newly diagnosed, while the rest had recurrent disease after treatment with either radiation or chemotherapy. They were tested for spread of the lymphoma. Only 3 had any spread, and this was to nearby lymph nodes. The patients were also tested for infection with C. psittaci. All were given doxycycline pills twice a day for 3 weeks, regardless of whether they were infected with the bacterium. There were no side effects from the doxycycline, which is a widely used antibiotic, and all participants completed their treatment.

What was found: More than half of the patients improved. In 6 patients the lymphoma disappeared completely. In another 7, it decreased to less than half of its original size, and in another 3 it decreased some, but not as much. Even among the patients who had no decrease in their tumors, most did not have any growth either.

Sometimes the response was slow, taking as long as 6 months to begin and up to 36 months before the shrinking had stopped. Even enlarged lymph nodes got smaller. Responses also occurred both in untreated patients and in those who had had been treated before with chemotherapy or radiation.

The responses were long lasting, too; most of the patients whose tumors shrank did not see any regrowth, at least for the average follow-up period of 21 months.

Although some of the patients did not have any infection with C. psittaci detected, this did not seem to affect their response. Similar numbers of people with and without the infection responded to treatment.

The bottom line: The authors say doxycycline appears to be a good alternative to radiation and chemotherapy for patients with eye lymphoma. It is safe, effective, and free of any serious side effects. However, until more studies are done to examine this therapy, they say patients should only get this treatment within a clinical trial. A clinical trial labeled IELSG 27 has started to look at the role of antibiotics in treating eye lymphomas and testing to see which antibiotics are the most effective.

Citation: "Bacteria-Eradicating Therapy with Doxycycline in Ocular Adnexal MALT Lymphoma: A Multicenter Prospective Trial." Published in the Oct. 4, 2006, Journal of the National Cancer Institute (Vol. 98, No. 19:1375-1382). First author: Andres J. M. Ferreri, San Raffaele H Scientific Institute, Milan, Italy.