BACKGROUND:The purpose of this study is to establish asimple and effective technique for the generation of an intrapulmonarytumormodel that yields solitary, localized intrapulmonary tumor, and to analyzethe highlights of the technique.
METHODS:After being anesthetized by slowintravenous injection of pentobarbital without oral endotracheal intubation, aright intercostal incision was made between the fifth and sixth ribs or at thenext intercostal space; the inferior lobe of the right lung was exposed. A16-gauge needle contained a strip of tumor tissue in the distal portion whichconnected to a 1.0-mL syringe that contained 0.1 mL air inside, was insertedinto the parenchyma at an estimated depth of 1.0 cm, and the air was injectedquickly to eject the tumor tissue into the pulmonary parenchyma. The air wasdrawn from the chest cavity by a race track, and the chest was closed. Thirtyanimals (Group A) received intrapulmonary tumor implantation (IPTI) asdescribed above, and 16 animals (Group B) received IPTI using a suspension ofsmall tumor fragment. Eight animals in each group were monitored by computedtomography (CT) scanning (Group CTA and CTB) and were used to determinesurvival time. Twenty-two animals in Group A and 8 animals in Group B weresacrificed and dissected at 21 d post-IPTI, followed by histologicalexamination.
RESULTS:Tumor take rate (tumor developed anywherein the chest) was 80% in Group A (24/30) and 75% in Group B (12/16); there wasno significant difference (P = 0.987). The rate of total chest seeding wassignificantly higher in Group B (66.7%, 8/12) than in Group A (12.5%, 3/24; P =0.002). At 3 wk post-IPTI, solitary, localized tumor foci developed at theimplantation site in 70% of Group A (21/30); this rate was significantly higherthan the 18.8% rate of tumor foci development in Group B animals (3/16; P =0.001). Twelve of the 16 animals monitored by CT scanning developed tumors.Among them, 7 animals that developed localized intrapulmonary tumors at earlytime post-IPTI survived significantly longer than the remaining 5 animals thatdeveloped extrapulmonary chest seeding tumors (P = 0.001). Intrapulmonarynodules after IPTI may develop granulomas, which were identified byhistological examination. Unidentified nodules were detected in CT images,which gradually decreased in size and eventually disappeared.
CONCLUSION:We establish a simple and effective methodfor the generation of an intrapulmonary tumor model that yields solitary,localized intrapulmonary tumor. The highlights of this technique are tumorquality control and tumor dissemination control. Extrapulmonary chest seedingat early time post-IPTI contributes to short survival. It is necessary tocharacterize the intrapulmonarynodules using histological methods prior to theevaluation of therapy; this approach may lead to a more accurate determinationof therapeutic outcomes.
