Zierenberg-Ripoll, Alexandra The Effects of Second-hand Smoke on Canine Lung Tumors Abstract Second-hand cigarette smoke is a recognized carcinogen, which has been shown to correlate with the development of pulmonary neoplasia in people. Dogs with spontaneous pulmonary cancer represent an interesting and unique population as they are exposed to similar environmental factors as the people with whom they live with. Thus, we propose that evaluation of dogs with primary lung tumors, especially those with documented exposure to chronic second-hand smoke from owners, would assist in determining the actual impact of second-hand smoke on the development of lung cancer. A survey study was developed and distributed to the owners of dogs in three target groups; a group with confirmed primary lung tumors (affected group), a group with cutaneous mast cell tumors (control group 1), and a group with neurologic dysfunction and no evidence of cancer (control group 2). Additionally, the radiographic features of lung tumors in dogs with and without documented tobacco smoke exposure will be compared to assess for features unique to smoke exposure. Preliminary results indicate that smoking occurred in 13% (10/79) of the households where dogs were diagnosed with primary lung tumors, 16% (9/55) of the households where dogs were diagnosed with mast cell tumors, and 6% (2/33) of the households where dogs needed neurologic evaluation. Data acquisition is ongoing. Goals The goals of this study are to 1) determine if exposure to tobacco smoke correlates with the development of primary pulmonary neoplasia in dogs and 2) characterize imaging features of the different types of primary lung tumors in dogs. We hypothesize that dogs exposed to cigarette smoke will have a higher incidence of pulmonary neoplasia and that the radiographic appearance of smoke induced tumors will be unique to other types of primary lung tumors. Materials and Methods Study Evaluation: Prior to commencing the proposed objective, a power statistical analysis was performed to determine the approximate number of dogs needed in the affected group and the number of dogs needed in the control groups. A two-group continuity corrected Ď‡2 test of equal proportions (odds ratio=1) (unequal nâ€™s). Assuming that 15% of responders were smokers, 374 lung cancer dogs would be needed with 747 control group dogs. The 747 control dogs were divided into the mast cell tumor group and the neurologic dysfunction with no other neoplasms group. Patient Selection: To reach the proposed objective, a search was performed within the database of the Veterinary Medicine Teaching Hospital at the University of California, Davis from January 2002 to May 2012. For inclusion in the primary lung tumor group, dogs must have had a cellular diagnosis of pulmonary carcinoma, adenocarcinoma, histiocytic sarcoma, or squamous cell carcinoma. Confirmation of disease was by biopsy, cytology, or necropsy. Two control groups were selected for comparison. Control group 1 included dogs with a histologic or cytologic diagnosis of cutaneous mast cell tumor and with no other neoplasms. Control group 2 consisted of dogs with neurologic dysfunction and with no other neoplasms.
Zierenberg-Ripoll, Alexandra Survey Development: A survey was developed and distributed by mail. Main survey topics included patient history, diet, exposure to flea medications, housing description, exposure to second-hand smoke and other inhaled products such as fertilizers and aerosols. Dog owners were instructed to answer questions about environmental exposure as they pertained to the last 5 years of the animalsâ€™ life prior to diagnosis. This survey also intended to quantify the amount of exposure to environmental toxins including tobacco. All three groups were given the same survey to complete. Imaging Assessment: When available, thoracic radiographs were reviewed for imaging features including type of pulmonary pattern as well as lesion size, number, location, margination, and distribution. The presence of lesion mineralization or cavitation, hilar lymph node enlargement and pleural effusion was recorded. Results Surveys were sent to owners of dogs with confirmed diagnosis of a primary lung cancer (affected group-284 cases), owners of dogs having a mast cell tumor (control group 1-260 cases), and owners of dogs requiring neurologic evaluation and with no evidence of cancer (control group 2263 cases). A total of 718 surveys were mailed. To date, 23% (167) surveys have been successfully received and recorded with preliminary results indicating that smoking occurred in 13% (10/79) of the households where dogs were diagnosed with primary lung tumors, 16% (9/55) of the households where dogs were diagnosed with mast cell tumors, and 6% (2/33) of the households where dogs needed neurologic evaluation. Surveys will continue to be analyzed as they arrive in the following weeks with the preliminary expectation that we will have to send a second round of surveys to maximize data collection. Thus, statistical analysis of our results will not occur until we have received and recorded as many surveys as possible. Moreover, radiographic assessment will not occur until we know which animalsâ€™ surveys are returned and, therefore, which images to evaluate. Should we not receive enough surveys to adequately assess the effect of second hand tobacco smoke on the development of lung cancer in dogs, we intend to recruit additional cases from another veterinary teaching institution. Summary In order to investigate tobacco smoke as an environmental toxin and to assess itsâ€™ detrimental health effects on dogs, we proposed to evaluate the home environment of owners with dogs diagnosed with primary lung cancer. This was assessed with the development of a survey that was distributed to 3 target groups (primary lung tumor, comparison group 1-mast cell tumor, and comparison group 2- neurologic consultation). Due to the preliminary stages of the study, final statistical results are still being processed as surveys are received.
Published on Dec 3, 2012