Comparison of gallium-67-citrate and thallium-201 scintigraphy in peripheral and intrathoracic lymphoma

We performed this study in an attempt to reconcile the differences with respect to 67Ga uptake as a function of tumor grade and type in the literature, as well as to determine the sensitivity of 201Tl uptake in both Hodgkin's and non-Hodgkin's lymphoma.

Thirty-six (9 with low-grade lymphoma, 11 with intermediate-grade lymphoma, 4 with high-grade lymphoma and 12 with Hodgkin's lymphoma) patients underwent both 67Ga and 201Tl scintigraphy. Biopsies were done on all patients. A semiquantitative rating system was used to make statistical comparisons for thallium versus gallium in all lymphoma subgroups, as well as comparisons of thallium and gallium to themselves in all subgroups.

Patient sensitivity was only 56% and site sensitivity was 32% in patients with low-grade lymphoma. Conversely, 201Tl sensitivity was 100%, respectively, for patients and sites. The difference between 201Tl and 67Ga sensitivity in patients with low-grade lymphoma on a site basis was statistically significant. When compared to itself in lymphoma subgroups, 201Tl was found to be statistically more avid for low-grade lymphoma than for intermediate, high or Hodgkin's lymphoma. Gallium-67 sensitivity for low-grade lymphoma was significantly less than for Hodgkin's and intermediate grade lymphomas. No significant differences were found when 201Tl and 67Ga were compared in the intermediate, high or Hodgkin's lymphoma groups.

Thallium-201 demonstrates significantly greater tumor avidity in the low-grade lymphoma group compared to 67Ga citrate. Gallium-67-citrate appears relatively nonavid for low-grade lymphoma compared to 201Tl and is statistically inferior in detecting low-grade lymphoma in comparison to its ability to detect intermediate or high-grade lymphomas. Gallium-67-citrate should not be considered dependable in evaluating patients with low-grade lymphoma. Neither 201Tl or 67Ga is dependable in the evaluation of low-grade lymphoma within the abdomen, since gallium avidity for low-grade lymphoma is low and gastrointestinal excretion of 201Tl is poorly controlled.