Patients are classified as having high tumour burden if they meet ≥1 of the following GELF criteria at assessment:

Criterion	Definition
Large tumour mass	Any nodal or extranodal tumour mass >7 cm in its greatest diameter.
Multiple nodal sites	Involvement of ≥3 nodal sites, each with a diameter >3 cm.
B symptoms	Fever >38°C, drenching night sweats, or unintentional weight loss >10% over 6 months.
Splenomegaly	Splenic enlargement with inferior margin below the umbilical line or symptomatic bulky spleen.
Compression syndrome	Organ compression due to lymphoma (for example ureteral, orbital, gastrointestinal).
Serous effusions	Pleural effusion or peritoneal ascites attributable to lymphoma, irrespective of cell content.
Leukaemic phase	>5.0×10⁹/L circulating malignant lymphoma cells.
Cytopenias	Granulocytes <1.0×10⁹/L and/or platelets <100×10⁹/L due to bone marrow involvement.

The calculator counts the number of criteria present (0–8). High tumour burden is defined as ≥1 GELF criterion present.

Groupe d'Etude des Lymphomes Folliculaires (GELF) Criteria