Table 661

Response criteria for non-Hodgkin's lymphoma according to International Workshop

Physical Lymph Lymph node

Response category examination nodes masses Bone marrow

CR Normal Normal Normal Normal

CRu Normal Normal Normal Indeterminate

Normal Normal >75% Decrease Normal or indeterminate

PR Normal Normal Normal Positive

Normal >50% decrease >50% decrease Irrelevant

Decrease in liver/spleen >50% decrease >50% decrease Irrelevant

Relapse/progression Enlarging liver/spleen, new sites New or increased New or increased Reappearance

• Appearance of any new lesion during or at the end of therapy

Relapse

• Appearance of any new lesion or increase by >50% in the size of any previously involved site

• More or equal to 50% increase in greatest diameter of any previously identified node greater than 1 cm in short axis or in the SPD of more than one node

At the time of the initial description of these criteria, response assessment was based entirely upon physical examination, and routine radiologic and pathologic criteria.

CT scanning was considered the standard imaging modality for nodal disease. The standardized criteria require assessment by CT scan no more than 2 months after completion of therapy. Bone marrow aspirate and biopsy is considered mandatory only to confirm CR if involved initially or if new abnormalities develop in the peripheral blood count or smear.

The Workshop also defined a series of acceptable endpoints for clinical trials as documented on Table 66.2.

In most studies of aggressive NHL, remission status, defined according to these criteria, is strongly correlated with outcome. In general, a partial remission after combination chemotherapy is associated with a high risk of subsequent relapse and a low probability for long-term disease-free survival. In studies of low-grade FL, this is less clear. Although many single center studies have demonstrated that the achievement of a CR to a particular regimen is associated with superior disease-free survival and overall survival compared with patients achieving a PR, comparative trials of different regimens have typically shown that higher response rates frequently correlate with higher rates of disease-free survival or event-free survival, but this rarely correlates with improved overall survival. There are several potential explanations for this, including the effectiveness of subsequent treatments to "rescue" patients who relapse after a particular regimen. However, recent data for new first line regimens in the treatment of FL suggest that these treatments may be improving overall survival in these diseases. If these observations are confirmed, the use of refined criteria for response in FL may become central to management. If the presence of residual subclinical disease in indolent lymphomas proves predictive of subsequent relapse and survival, the potential for early treatment will require investigation.

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