International Prognostic Index

The International Prognostic Index (IPI) is a clinical tool developed by oncologists to aid in predicting the prognosis of patients with aggressive non-Hodgkin's lymphoma. Prior to 1993, when the IPI was developed, the primary consideration in assessing prognosis was the Ann Arbor stage alone, but this was increasingly found to be an inadequate means of predicting survival outcomes, and so other factors were studied.

A retrospective analysis was performed on 2031 patients with aggressive non-Hodgkin's lymphoma, of all ages, treated with a doxorubicin-based chemotherapy regimen such as CHOP between 1982 and 1987. Several patient characteristics were analyzed to determine whether they were associated with differences in survival, and the factors that emerged as significant were, in addition to the Ann Arbor stage: age, elevated serum lactate dehydrogenase (LDH), performance status, and number of extranodal sites of disease.

One point is assigned for each of the following risk factors:

The sum of the points allotted correlates with the following risk groups:

A simplified index can be used when comparing patients within an age group (i.e. 60 or younger, or over 60) and includes only 3 of the above factors:

The sum of the points allotted correlates with the following risk groups:

Although the IPI has shown itself to be a useful clinical tool, widely used by oncologists and a mainstay of risk stratification in clinical trials for lymphoma, it should be kept in mind that it was developed prior to the use of rituximab, which is now included with anthracycline-based combination chemotherapy as of the standard of care in B-cell lymphomas (the majority of non-Hodgkin's lymphomas). Rituximab has dramatically improved the outcomes of lymphoma patients, and its effect on the prognostic value of the IPI is uncertain.

Given the success of the IPI for intermediate grade lymphomas, an effort was undertaken to develop a similar prognostic index for the most common low-grade lymphoma, follicular lymphoma. The prognostic factors that emerged from this were: age, stage, number of lymph node areas involved, serum hemoglobin level, and serum LDH.

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