When is hilar uptake of Ga-67-citrate indicative of residual disease afterCHOP chemotherapy?

The purpose of this study was to evaluate the prevalence and characterize t he patterns of hilar uptake (HU) on Ga-67-citrate imaging after cyclophosph amide, doxorubicin, vincristine, and prednisone (CHOP) chemotherapy regimen s for non-Hodgkin's lymphoma (NHL), to differentiate hilar lymphoma (HL) fr om HU of benign etiology. Methods: A total of 930 studies (698 planar, 232 thoracic SPECT) was reviewed retrospectively in 100 NHL patients (29 low-gr ade, 60 intermediate-grade, and 11 high-grade) treated with CHOP and follow ed up longitudinally with serial gallium studies (planar: median, 7; range, 3-16 studies in 100 patients; SPECT: median, 1; range, 0-11 studies in 72 patients) over a median duration of 36 mo (range, 6-112 mo) from diagnosis. Clinical outcome and size changes over time on correlative CT and/or radio graphs were used to evaluate benign versus malignant changes within the hil a. Results: HU after CHOP was present in 79% of patients (90% confidence in terval [CI], 71%-85%), with 33% showing HU on SPECT alone. Once present, HU persisted for a median of 27 mo (range, 2-84 mo) from onset. The prevalenc e of HU and HL at various time points was as follows: baseline HU, 52% with HL 60%; mid-CHOP HU, 59% with HL 2%; post-CHOP HU, 52% with HL 6%; follow- up HU, 76% with HL 9%. HU of benign etiology was not significantly correlat ed with CHOP dosage. HU was symmetric in 90% of patients (90% CI, 82%-95%) and less intense than the original disease in 89% of patients (90% CI, 80%- 95%), and these features were highly predictive of benign etiology (negativ e predictive value [NPV], 98.6% if symmetric; NPV, 96.5% if less than origi nal disease; NPV, 100% if both present). Asymmetric HU equal in intensity t o the original disease, however, was highly predictive of HL (positive pred ictive Value [PPV], 87.5% if asymmetric; PPV, 85.7% if equal to original di sease; PPV, 100% if both present). Conclusion: HU after CHOP is common (ove rall incidence, 79%), often seen only on SPECT, and most likely of benign e tiology when symmetric and less intense than the original disease. Asymmetr ic HU that equals the intensity of the original disease, however, is a poss ible indicator for HL.