肺血流スキャンを用いた肺癌の非観血的治療の評価

摘要

肺癌の化学療法や放射線治療の前後で肺血流スキャンを施行した91例を対象に,肺スキャンを用いて生理学的な観点から治療効果を評価した.治療前,後の患側肺の血流比をp,q,全肺血流量をQ,Q′と定め,健側肺の肺血流量は治療前後で不変であると仮定すると,全肺血流分布に対する患側肺の血流の改善された度合いを意味する肺血流改善比(Improvement Ratio; IR)はIR=qQ′/pQ=(1-p)q/p(1-q)と定義される. IRを用いて従来の解剖学的な評価法や,腫瘍の局在,細胞型,予後との関係について検討を試みた.治療効果がみられたcR,PRの症例群では有意にIRは高値となり肺血流が改善していたが,中にはIR<1で悪化する例も存在した.肺門型,小細胞肺癌の群では有意な肺血流の改善が認められ,肺血流の改善が予後の改善にも影響を及ぼした.肺癌の総合的な治療効果判定に肺血流スキャンなどの生理学的な機能改善を考慮することが有用であると考えられた.The purpose of this prospective study was to follow the changes in functional parameters of radionuclide lung perfusion scans and their role in prognostication of lung cancer cases after noninvasive therapy. We studied 91 patients of lung cancer treated with chemotherapy and/or radiotherapy during 1993 to 1997 in our hospital. Lung perfusion scans were acquired pre and post-therapy. An index of lung perfusion,called Improvement Ratio (IR) was defined as a change in the perfusion of diseased lung as a result of treatment. IR was calculated by the following equation under the assumption that perfusion of contralateral lung remained unaffected.where Q and Q' are pulmonary arterial blood flow pre and post therapy respectively,p is prefusion ratio of diseased lung before therapy and q is that after therapy. We further studied the relationship between IR and change in tumor size. The influence of tumor location,histopathological diagnosis and prognosis of lung cancer were correlated with this newly defined index. IR in the group of patients with complete re-sponse or partial response was significantly higher than in those with poor response (2.72 ((+-)-)0.78 versus 0.99 ((+-)-) 0.09,p<0.05). There was no statistical difference between the group with and without radiotherapy. The score was significantly higher for patients with hilar disease compared to those with peripheral lesions (2.80 ((+-)-) 0.83 versus 1.02 ((+-)-) 0.03,p<0.05). Similarly,patients with small cell lung cancer depicted higher values of IR than non-small cell lung cancer (3.36 ((+-)-) 1.10 versus 1.06 ((+-)-) 0.07,p<0.05). All those subjects who showed IR> 1 had longer survival time than those with IR< 1 (p<0.05). It is suggested that improvement in the perfusion of diseased lung predicted better prognosis.We conclude that the evaluation of physiological parameters during therapy using lung perfusion scanning,in addition to lesion size assessment will contribute to the comprehensive follow-up of lung cancer.