Fig. 3.

The impact of filter and flow characteristics on estimation of the metastatic efficiency index (MEI). We have compared Weiss’ original method (rescaled to be comparable, see Section 2) with our filter-flow framework under the assumption of no micrometastases, micrometastases in the lung, in the liver, and in both locations. The comparison is carried out for five organ pairs that cover the canonical pathways of spread (gut → body, body → body, lung → body, body → liver and gut → lung). We see that because Weiss’ method only considers the dynamics on the arterial side (and disregards the filtration in the liver) it provides a smaller MEI in three of the cases (pancreas → kidney, bladder → liver and colon → lung). From the comparison it is also evident that assumptions about the presence or absence of micrometastases heavily influences the results, in the case of pancreas → kidney shifting the MEI two orders of magnitude.