Determining which factors influence survival after surgical removal of primary lung tumors was the purpose of this retrospective study. The study included 20 client owned cats undergoing surgical resection of a primary lung tumor between 2000 and 2007. Data was recorded from a review of patient records for signalment, clinical signs, preoperative diagnostics, surgical findings and histopathologic results. World Health Organization (WHO) scoring was used on review of the histopathologic reports and for tumor staging.
The WHO TNM system for primary pulmonary tumors utilizes the following designations: T1= solitary lung tumor, T2= multiple tumors in one lung lobe, T3= tumor invading adjacent tissues; N0 = no nodal involvement, N1 = tracheobronchial lymph node positive, N2 = extra thoracic lymph node positive; M0 = no pleural or distant metastasis, M1 = pleural or distant metastasis evident.
Thoracic radiography was performed in all 20 cases. 13 cats had a solitary lung mass. Right (50%) and left (40%) lung fields were represented almost equally. (10% had tumor in both lung fields). 11 cats had single lung lobectomies and 9 cats had multiple lung lobes removed. Caudal lung lobes were more commonly affected than cranial lobes. Lymph node biopsy was performed if the nodes were visually enlarged.
The most common clinical signs were anorexia, coughing, lethargy, weight loss, dyspnea, and dysphagia. Dyspnea was the one sign that was significantly associated with a shorter survival time (median survival time of 2 days) versus cats without dyspnea (median survival time of 31 days). Presence of pleural effusion was significantly noted to be associated with a shorter survival. 18 of 20 cats (90%) were diagnosed with adenocarcinomas. Patients with well-differentiated tumors also had significantly longer survival times than cats with moderately or poorly differentiated tumors. Staging was an additional significant prognostic factor. Cats staged T1N0M0 lived longer than cats with other stages. The median survival time of T1N0M0 cats was 190 days compared to 3 days for cats with other stages. They also noted that cats that presented with no clinical signs had a median survival time post-surgery of 578 days versus 4 days post-surgery in cats presenting with clinical signs.
Results of this study strongly indicated that when there was the presence of respiratory signs, pleural effusion, any stage beyond T1N0M0, evidence of metastasis, and moderately to poorly differentiated tumors, these factors were negative prognostic indicators for cats with primary lung tumors. Using the WHO staging system was found to be important for prognosis in such cases. Fine needle aspirates were found as a preoperative test to have a low sensitivity since 40% of the results were not diagnostic. The authors also stated that as the result of this study they will not operate on cats with primary lung tumors noted on radiographs without using preoperative computed tomography (CT) scan. CT is a better tool to evaluate lymph node involvement and determine metastasis as part of staging. Cats presenting with no clinical signs at the time of diagnosis have a better prognosis than cats exhibiting clinical signs when diagnosed. In addition, the authors state the study’s results brings into question whether surgery should be pursued in cats that present with dyspnea and/or pleural effusion. (VT)