New guidelines covering all types of lymphoma developed by the International Harmonization Project build on guidelines published in 1999 to provide clinicians with uniform criteria to evaluate response to treatment and interpret data from clinical trials, according to an article in the February 10 issue of the Journal of Clinical Oncology.

Although the 1999 criteria had been widely adopted by clinicians and regulatory agencies and used to approve several treatments, recent advances, including increased use of positron emission tomography and immunohistochemistry in assessment of response to treatment prompted the Project to substantially revise the criteria.

The recommendations aim to standardize the parameters used in clinical trials for lymphoma and incorporate new technologies. In addition, the revised guidelines cover all lymphomas. Bruce Cheson, MD, professor of medicine at the Lombardi Comprehensive Cancer Center at Georgetown University Hospital, is senior author of the paper and led the revision effort.

Integration of positron emission tomography represents a major change in the guidelines. Malik Juweid, MD, associate professor of radiology at the UI Roy J. and Lucille A. Carver College of Medicine and a member of the UI Holden Comprehensive Cancer Center, was co-chair of the IHP committee that developed the recommendations for performing and interpreting PET scans in response assessment of lymphoma. The imaging committee, which included world-renowned imaging experts from the United States, Europe and Australia, was co-chaired by Sigrid Stroobants from University Hospital Gasthuisberg in Leuven, Belgium.

"This is the first time that standardized guidelines have been recommended on an international level," Juweid said. "These revised criteria for response assessment of lymphoma are unique in that they are the first for any cancer type to formally integrate functional imaging with positron emission tomography into the more conventional response assessment using clinical, laboratory and radiological measures."

In contrast to conventional computed tomography or magnetic resonance imaging, positron emission tomography (PET) is able to distinguish between viable tumor and non-cancerous scar tissue that is often left behind after successful treatment of lymphoma. Incorporation of PET imaging into response assessment means that doctors can more accurately determine the nature of any residual mass and essentially rule out persistent cancer within the mass if the scan is PET-negative. This approach will allow researchers to accurately assess how well anti-lymphoma drugs work even when there is a residual mass at the tumor site following treatment.

"Many patients with either diffuse large B-cell lymphoma (DLBCL), which is the most common subtype of lymphoma, or Hodgkin's disease, who were previously considered in partial response to treatment based on the conventional assessment, will now be considered in complete response if their PET scan is negative. Such patients can be safely observed and are expected to have an excellent outcome," Juweid said.

In contrast, Juweid added, the smaller fraction of such patients who are PET-positive after treatment should undergo a biopsy to evaluate the PET-positive lesion unless there already is other compelling clinical and/or biochemical suspicion of persistent disease. If the biopsy is positive, these patients can rapidly be considered for salvage therapy.

The revised guidelines cover the use of PET for assessing all types of lymphoma. For two potentially curable types of lymphoma, DLBCL and Hodgkin's disease, the guidelines recommend that PET always be used to assess post-treatment response. PET also is strongly recommended prior to treatment to determine extent of disease for these lymphomas.

For the other 30 or so other subtypes of lymphoma, most of which are less common, the guidelines offer recommendations for when PET is useful and when it is not, and if PET is used in those cases, what criteria should be fulfilled.