Abstract
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Objectives: Fractionated therapy with 177Lu-octreotate is an effective treatment option for patients with generalized neuroendocrine tumors. The most frequent protocol in therapy with 177Lu-octreotate is to give all patients 4 cycles with 7.4 GBq each time. The current aim was to study method possible gender difference in absorbed doses to risk organs in patients receiving therapy with 177Lu-octreotate.
Methods: Five hundred patients (250 female and 250 male) with neuroendocrine tumors with high somatostatin receptor expression were included. SPECT/CT images were acquired at 24, 96 and 168 h after infusion of 7.4 GBq of 177Lu-octreotate and attenuation corrected SPECT images was created. Absorbed doses were calculated using small VOIs as described earlier (1). The median, min and max of the absorbed doses for the spleen, liver, right kidney and left kidney for women and men separately were calculated. Then the results for each organ was compared for the women versus the men. The comparison was made using an unpaired nonparametic Mann-Whitney test. P-values less than 0.05 was treated as significant and P-values less than 0.001 was treated as highly significant. 1. Sandstrom M, Garske U, Granberg D, Sundin A, Lundqvist H. Individualized dosimetry in patients undergoing therapy with (177)Lu-DOTA-D-Phe (1)-Tyr (3)-octreotate. Eur J Nucl Med Mol Imaging. 2010;37:212-225.
Results: The absorbed doses in the spleen were for women 4.7 (0.6-25.5) Gy (Median (Min-Max))) and for men 5.0 (0.3-12.6) Gy with a P-value of 0.38 and for the liver the absorbed doses to the women were 2.1 (0.6-15.2) Gy and for men 2.1 (0.2-12.5) Gy with a P-value of 0.75 so there was no significant statistical difference for spleen and liver. The absorbed dose in the right kidneys were for women 4.9 (2.1-12.6) Gy and for men 3.9 (2.0-9.7) Gy and for the left kidney 4.6 (1.0-9.8) Gy for women and 3.8 (1.5-8.5) Gy for men with a P-value of <0.0001 so this was highly significant. So there were no significant gender difference for spleen and liver while the gender difference was highly significant for both right and left kidneys. This may be due to just gender differences or that women and men generally differ in weight and that the difference is weight correlated, but the difference is at least clear.
Conclusion: There is a clear gender difference between the absorbed doses to the main risk organ in patients receiving 177Lu-octreotate therapy. So the most frequent protocol in therapy with 177Lu-octreotate with 4 cycles with 7.4 GBq each time seems not sufficient. Instead all therapies should be individualized and the individual absorbed doses should be calculated. Research Support: None