Burkitt lympohoma (BL) is a rare high-grade B-cell lymphoma, which in most cases is studied in small numbers. Definitions of low-risk BL vary, and until now arbitrary cut-off values have been used regarding lactate dehydrogenase. On top of that more than 80 percent of the patients would end up in a further undifferentiated high-risk group. Therefore, there was an urgent need for a practical prognostic index for BL patients. This would help to provide a more adequate patient care, the possiblitity to compare results from clinical studies and to develop novel targeted treatment approaches.
The investigators derived the international prognostic index (BL-IPI) from a large historical cohort (n=633) from adults treated for BL in de United States during the period of 2009 till 2018. Primary outcome was progression-free survival (PFS) from diagnosis until BL recurrence, progression, death, or censoring, in order to identify candidate variables with the strongest prognostic association with PFS. Subsequently the index was validated in an external dataset (n=457) of patients treated in Europe, Canada and Australia between 2004 and 2019.
Four equally weighted factors were identified: age ≥ 40 years, performance status ≥ 2, serum lactate dehydrogenase > 3× upper limit of normal, and CNS involvement. This resulted in the following stratification. Patients with zero risk factors were classified as low-risk. This was the case for 18 percent of the people in the training cohort, who had a 3-year PFS of 92 percent. Patients with 1 risk factor were classified as intermediate risk. This groups consisted of 36 percent of the patients and showed a 3-year PFS of 72 percent. Finally the high-risk group, which contained BL patients with 2 or more risk factors. Forty-six percent was classified as such and had a 3-year PFS of 59 percent. The index discriminated clinical outcomes regardless of HIV status, stage or first-line chemotherapy regimen.
The relative risk group sizes in the validation cohort were similar to the training cohort. The 3-year PFS percentages were comparable as well with 96, 82 and 63 percent for low, intermediate and high-risk, respectively.
The BL-IPI is a new practical prognostic index. It can serve as a robust tool for adult BL patients to predict survival more accurately. In addition the index can be used to stratify patients in clinical trials. Currently, In particular the high-risk group has suboptimal outcomes with standard therapy. Development of novel treatment strategies for these patients is warranted.
Olszewski AJ, Jakobson LH, Collins GP, et al. Burkitt Lymphoma International Prognostic Index. J Clin Oncol 2021; doi:10.1200/JCO.20.03288.