An update on diagnosing and treating primary lung tumors - Veterinary Medicine
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An update on diagnosing and treating primary lung tumors
The incidence of this rare cancer in dogs and cats may be on the rise. Find out how to spot a primary lung tumor and what new forms of therapy may soon be at your disposal.


VETERINARY MEDICINE


TREATMENT

The treatment of choice for solitary primary pulmonary tumors in dogs and cats is wide surgical resection—either a complete lung lobectomy or a partial lobectomy if the tumor is in the periphery.27,48 However, in cats more often than dogs, even if a single pulmonary nodule is seen radiographically, it is not uncommon to find multiple small lesions at surgery, suggesting the importance of advanced diagnostic imaging (CT or magnetic resonance imaging) before surgery.1

Surgery

Given the advent of fiberoptic technologies and the training of surgical residents in noninvasive techniques, thoracoscopic lung lobectomy is becoming a more common surgical approach for managing lung tumors in companion animals. When compared with thoracotomy in people, the results of thoracoscopy are less tissue trauma, decreased morbidity, shorter hospitalization, and earlier return to normal activity.49 Adequate exposure of the thoracic cavity and access to the hilar lymph nodes may still require conventional thoracotomy, so thoracoscopic procedures are best suited for removing small, peripherally located masses.48

For conventional thoracotomy, a lateral intercostal surgical approach allows access to the primary bronchi for lobectomy of the side involved but prevents adequate examination of the opposite hemithorax. During thoracotomy, examine and palpate all accessible lung lobes and tracheobronchial lymph nodes for metastasis or multifocal primary masses. If the tracheobronchial lymph nodes appear enlarged, they should at least be biopsied and preferentially be extirpated.

Adjuvant chemotherapy

After the primary tumor and associated draining lymph nodes are removed, adjunctive chemotherapy may be warranted based on host factors (clinical stage) and tumor characteristics (histologic findings). Despite the availability of new chemotherapeutic drugs, few well-designed prospective studies have investigated the efficacy of one or multiple agents for treating primary pulmonary neoplasms in dogs and cats.

Vinorelbine, a semisynthetic derivative of vinca alkaloids, has recently been described for treating various neoplasms, including primary lung tumors, in dogs.50 Vinorelbine is widely distributed in all tissues except for the brain, with concentrations in the lungs reaching 13.8-fold higher than other vinca alkaloids.51 In one study, two of seven dogs with macroscopic bronchoalveolar carcinoma achieved a partial remission after vinorelbine treatment. Furthermore, in dogs with microscopic bronchoalveolar carcinoma (incompletely excised primary or lymph node metastases), vinorelbine's anticancer activity was suggested by the relatively durable survival times of 113, 196, and 730+ days in three dogs treated with surgery and systemic vinorelbine.50 Further investigations are warranted to determine the effectiveness of adjunctive vinorelbine for treating bronchoalveolar carcinomas as well as other pulmonary neoplasms in dogs.

In a study of 15 dogs with primary lung tumors treated by lobectomy, five dogs with advanced recurrent pulmonary carcinoma received one of three chemotherapy protocols: 1) cyclophosphamide, vincristine, and methotrexate, 2) vindesine alone, or 3) vindesine and cisplatin.8 Two dogs treated with vindesine and cisplatin showed partial responses, with greater than 50% reduction in radiographic lesions. Anorexia was the only side effect of the cyclophosphamide, vincristine, and methotrexate protocol, while reversible neurotoxicity was the only side effect of vindesine alone. In the dogs treated with vindesine and cisplatin, mild leukopenia and gastrointestinal upset were seen in both dogs, while only one dog experienced reversible peripheral neurotoxicity consisting of rear limb weakness and decreased patellar reflexes.8 The anecdotal favorable response observed in the two dogs treated with cisplatin and vindesine, along with this protocol's acceptable toxicity profile, warrants further studies examining this combination of chemotherapeutic agents for treating primary lung cancer, especially adenocarcinomas.8


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Source: VETERINARY MEDICINE,
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