Nefritis intersticial demostrada mediante gammagrafía con 67Ga-citrato en el contexto de fiebre de origen desconocido

Evaluation of doxorubicin-induced early multi-organ toxicity in male CD1 mice by biodistribution of 18F-FDG and 67Ga-citrate. Pilot study

The search for methods that identify early toxicity, induced by chemotherapy, is urgent. Changes in the biodistribution of radiopharmaceuticals could give information on early toxicity. Ten-week-old CD1 male mice were divided into four groups. Two groups were administered a weekly dose of 5 mg/kg of doxorubicin hydrochloride (DOX) for 5 weeks and the control groups were administered saline solution. One week after the end of treatment, the biodistribution of ¹⁸F-FDG and ⁶⁷Ga-citrate were carried out, as was the quantification of plasma enzymes CK, CK-MB, LDH and AST. All enzymes were higher in the treated animals, but only significant (p < 0.05) in the case of CK-MB. ¹⁸F-FDG uptake increased in all organs of treated animals except retroperitoneal fat, being significant in spleen, brain, heart, liver, lung, kidney, and inguinal fat. ⁶⁷Ga-citrate had a more complex pattern. The uptake in the DOX group was higher in spleen, lung, kidney, testes, and gonadal fat, it did not change in brain, heart, and liver, and it was lower in the rest of the organs. It only showed significant differences in lung and pancreas. A thorough discussion of the possible causes that produced the change in biodistributions of both radiopharmaceuticals is included. The pilot study showed that both radiopharmaceuticals could identify early multi-organ toxicity induced by DOX. Although ¹⁸F-FDG seems to be better, ⁶⁷Ga-citrato should not be ruled out a priori. The detection of early toxicity would serve to adopt treatments that prevent its progression, thus improving patient's quality of life.

Absolute Quantitative Evaluation of 67Ga Scintigraphy in Lupus Nephritis

PURPOSE

Renal biopsy is crucial for management of lupus nephritis. However, it is invasive and can cause bleeding and infection. In our previous study, we developed a semiquantitative method for gallium renal imaging and demonstrated a good correlation between the left kidney-to-spine ratio (K/S ratio) and the results of renal biopsy. However, the accuracy of left K/S ratio is compromised by the variation of spinal gallium uptake, especially in patients with extraordinarily high or low gallium uptakes in the spine. In this study, we developed an absolute quantitative method and compared the results of quantitative gallium images, semiquantitative gallium images, visual methods, and renal biopsies.

METHODS

Thirty-four patients with lupus nephritis were enrolled and underwent renal biopsy to determine activity index (AI) and chronicity index. A delayed 48-hour gallium scan was also performed and interpreted by visual, semiquantitative, and absolute quantitative methods. For absolute quantitative analysis, a standard solution with activities of approximately 555 KBq (15 μCi) was prepared and poured into a 5-mL tube, which was placed close to the patient. ROIs were drawn around the outer edge of the left kidney as well as around the outer edges of the standard. A kidney uptake index (KUI) was calculated, and the results were compared with K/S ratio, visual grading, and renal biopsies.

RESULTS

Kidney uptake index had the best correlation with AI among the 3 methods using Spearman rank correlation test. The Spearman R values were 0.78, 0.71, and 0.61 for KUI, K/S ratio and visual grading, respectively. Chronicity index did not correlate well with the results of any of the 3 methods. In addition, AI was significantly higher in patients with a KUI equal to or greater than 1.5, when compared with patients with a KUI lower than 1.5 (P = 0.00001 by Mann-Whitney U test). Using a K/S ratio of 0.95 as a cutoff value, AI also showed a statistically significant difference with P = 0.0001. When a visual grading of 2 was used as a cutoff value, P = 0.0008. The difference in AI was most significant when the statistical value was based on the KUI.

CONCLUSIONS

The KUI showed better correlation with the results of renal biopsy than the K/S ratio and the visual grading. We suggest that the KUI from the absolute quantitative renal gallium scintigraphy may be a useful parameter for evaluating the disease activity in lupus nephritis.