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CT measurement of blood flow through lung cancers.

Editor: In “Assessment of Non–Small Cell Lung Cancer Perfusion: Pathologic-CT Correlation in 15 Patients” ( 1 ), which appeared in the December 2010 issue of Radiology , Dr Tacelli and colleagues list no imaging references prior to the advent of computed tomography (CT). The paucity of pre-CT references may be owing to diffi culties in fi nding earlier articles. The following facts were documented over 40 years ago: 1. Lung tumors are supplied by both bronchial and pulmonary circulations ( 2 ). This article, as confi rmed by distinguished respiratory pathologist Averill Liebow (written communication, September 1975 ), reversed the dogma that lung tumors have a purely bronchial circulation. 2. Peripheral tumors, both primary and metastatic, have a predominantly pulmonary circulation; central tumors have a predominantly bronchial circulation ( 3 , 4 ). Related to this, peripheral tumor perfusion is approximately 2.4 times central tumor perfusion ( 5 ). Dr Tacelli and colleagues suggest that perfusion discrepancies between similar tumors are based on interstital pressure; however, interstitial pressure increases only in tumors within a confi ned environment ( 6 ). The lung is the least confi ning tissue in the body. A more likely cause is variation in the perivascular tumor compliance ( 3 ). Another unmentioned factor is intravascular hydrostatic pressure, which is predictably fi ve times higher in central tumors (bronchial circulation) than in peripheral tumors (pulmonary circulation.). Dr Tacelli and colleagues state there is no correlation between the histologic nature of a lung cancer and the amount of angiogenesis. As stated, this appears incorrect ( 6 , 7 ). If they meant to say there is no correlation between grades of tumor of the same histologic type, I would agree. One certainly hopes it will become possible to measure perfusion in tumors small enough for chemotoxic intervention to be benefi cial, but I am concerned that the authors’ statement that “whole-tumor perfusion analysis is achievable with CT, enabling qualitative and quantitative assessment of lung tumor neovascularization” is premature since there are marked discrepancies, as they document, between their CT fl ow measurements and pathologic confi rmation. Dr Tacelli and colleagues presumably intend to perfect their technique; might the present article therefore be considered a work in progress? I look forward to their future papers in which some or all of the measurement problems will have been solved.