Background: Scintimammography with 99mTc-MIBI has been proven as efficient technique of diagnosis of breast cancer. Nevertheless, quantification of breast carcinoma blood flow (BCBF) in absolute units is not yet developed. To compensate this, we analysed kinetics of 99mTc-MIBI uptake in breast cancer using Gjedde-Rutland-Patlak (GRP) approach.
Methods: If BC is radioactivity in breast cancer quantified by dynamic scintigraphy, Ch-blood concentration of 99mTc-MIBI and K - transport constant, then, assuming 99mTc-MIBI uptake to breast carcinoma unidirectional for early minutes after injection and subjected to equation d(BC)/dt = K ´ Ch, classic GRP plot can be obtained from this by integration as BC/Ch=K´(ňChdt)/Ch + V0 and placing {(ňChdt)/Ch} as X, and (A/Ch) as Y. The K can be then obtained as slope. K is breast cancer clearance equal to product (retention fraction) ´ (blood flow) : K = E ´ BCBF. K can be calculated from A(t) and Ch(t) as asymptote of 99mTc-MIBI retention function h(t) = F-1{F[A(t)]/F[Ch(t)]}, where F depicts Fourier transforms. The BCBF can be then obtained as ratio K/E. We employed the technique in 33 patients with breast carcinoma of stages T1-3N0-3M0-1 injecting 99mTc-MIBI (370-510 MBq) as i.v. bolus. In 12 scintigraphy with 99mTc-MAA (370 MBq) injected via catheter intraaortically was performed as validation study.
Results: E values were essentially uniform over the population with overall mean 0.58 sd 0.06. Blood clearance curves did not differ between various stages also and were subjected to biexponential approximation. K was in all cases obtained from the slope of initial 3 min part of GRP plot, strongly linear (r > 0.95, p < 0.001) in all cases. 99mTc-MAA validation study revealed significant correlation with 99mTc-MIBI blood flow values (r = 0.94, p < 0.01). The BCBF(as ml/min/100 cm3) was in T1 12,85 sd. 4,76, in T2 15,87 sd. 1,78, in T3 17,35 sd. 2,45, and in T4 23,07 sd. 2,21, expressing tendency to increase with stage. Higher BCBF was significantly associated with metastatic spread and in patients with BCBF over 17 ml/min/100 cm3 distant mets were revealed in all cases.
Conclusion: Hence, analysis of early kinetics of 99mTc-MIBI in breast carcinoma provides correct estimates of blood flow in the neoplasm and can be applied in clinical studies and for calculation of cytostatic delivery to BC.