Page 535 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 24 Tumors of the Respiratory System 513

an electrode within a tumor and generating heat; the heat results not statistically significant, the mean ST of dogs with SCC was
in coagulative necrosis in a defined region. 365,367,368 The goal is to 8 months and the mean ST of dogs with adenocarcinoma was 19
282
months in one study.
produce a 360-degree region of necrosis around the tumor with
VetBooks.ir a 1 cm thick margin of normal tissue included. 365,367 RFA has and based the prognostic evaluation on the WHO classification
A recent study evaluated 42 dogs with primary lung tumors
been performed in dogs with experimentally induced transmis-
sible venereal tumor of the lung. 370 In five dogs, RFA was applied scheme. 374 In these cases, 34 tumors were carcinomas (26 papil-
percutaneously with CT guidance to 14 tumors. Upon harvest lary adenocarcinomas) and eight were sarcomas. Fourteen of the
of the affected lung lobes, gross and histopathologic evaluations carcinomas and two of the sarcomas were T1N0M0. Dogs with
demonstrated complete thermal coagulation necrosis of all treated papillary adenocarcinomas and a clinical stage of T1N0M0 had
lesions, and viable tumor was not identified in any dogs. 370 the best overall prognosis with an MST of 555 days; this ST was
Regional chemotherapy has been developed with the goal of significantly longer than dogs with any other tumor type or dogs
increasing the efficacy of chemotherapy agents and decreasing with a worse clinical stage. 374 Dogs with other tumor types had an
systemic side effects. 371 Regional delivery allows for increased MST of 72 days. 374
concentrations of chemotherapy to be delivered to the tumor by In regard to localized HS, one retrospective study reported that
selective catheterization of the tumoral arterial supply. 371 Regional surgical excision and adjuvant therapy with CCNU resulted in an
techniques involving the administration of chemotherapy into the MST of 568 days. 355 Interestingly, five out of 16 dogs within that
bronchial arteries and pulmonary arteries have been described study had localized pulmonary lesions.
in several human studies. 369,371,372 Recently, in an experimental The prognosis is guarded to poor for cats with primary lung
model study, significantly higher concentrations of chemotherapy carcinomas. In one retrospective study of 21 cats treated with lung
agents (gemcitabine and carboplatin) were noted in pulmonary lobectomy, 286 the overall MST was 115 days. The only prognostic
tissue treated with regional techniques (selective pulmonary artery factor in this study was histologic grade; the MST for cats with
perfusion) than intravenous administration. 372 The indications moderately differentiated carcinomas was 698 days compared with
and clinical use of these treatments, while developing, still remains only 75 days for cats with poorly differentiated carcinomas. In a
to be determined in veterinary patients. separate study, cats with low-grade tumors had an MST of 730
days compared with 105 days for cats with high-grade tumors. 287
Prognosis Similar to dogs, LN enlargement in cats significantly decreased
MST to 65 days from 498 days for cats with no evidence of
In one clinical study of 67 dogs undergoing removal of primary lymphadenomegaly. 287 The TNM staging scheme also correlated
lung tumors, the overall MST was 361 days. 281 Prognostic fac- with ST in cats; cats staged T1N0M0 live significantly longer than
tors included the presence of clinical signs, clinical stage, tumor cats with higher stages. 286 In this same study, the MST in cats
type, and histologic grade. Dogs with clinical signs associated with clinical signs was 4 days compared with 578 days in asymp-
with a primary lung tumor had an MST of 240 days compared tomatic cats. 289 Pleural effusion has been identified as a negative
with 545 days for asymptomatic dogs. Dogs with single solitary prognostic factor; in two studies, the MST were less than 3 days
lung tumors (T1 clinical stage) had an MST of 790 days, which and 31 to 467 days in cats with and without pleural effusion,
was significantly longer than dogs with multiple lung tumors (T2 respectively. 287,289
clinical stage, 196 days) and dogs with lung tumors invading into
adjacent structures (T3 clinical stage, 81 days). Finally, the MST Comparative Aspects
for dogs with grade I lung carcinomas was 790 days, and this was
significantly longer than the MSTs of 251 days and 5 days for dogs Lung cancer is the leading cause of cancer deaths in the United
with grade II and III lung carcinomas, respectively. 281 States and worldwide. 375 Approximately 85% of human lung can-
One study evaluated the effect of several variables on remis- cers are NSCLC, with the remainder being small-cell lung cancer.
sion and survival in dogs with primary lung tumors. 373 Dogs for NSCLC are composed of three distinct histologic subtypes: SCC,
which surgery was successful in rendering them free of macro- adenocarcinoma, and large-cell lung cancer. Large airway origin
scopic disease lived significantly longer than dogs that had gross tumors predominated in humans through the 1960s and were
disease postoperatively. 373 Factors significantly associated with commonly associated with smoking cigarettes. Adenocarcinoma
remission included limited degree of primary tumor involvement, arising from the smaller airways now predominates in human
normal sized LNs, and lack of metastatic disease. 373 In a separate patients, likely a result of changes to tobacco blends and the use
study of 15 dogs, trends for longer STs were noted in dogs with of cigarette filters. 376
adenocarcinoma versus SCC, dogs with peripheral lesions versus If curative-intent resection can be performed, prognosis for
lesions that involved an entire lobe, and dogs with tumor volume human patients with NSCLC is largely dependent on clini-
3
<100 cm compared with dogs with tumor volume >100 cm . cal stage with 5-year survival rates greater than 60% to 70% for
3 282
The MST for dogs with no evidence of LN (N0) was 452 days, patients with stage I disease. Five-year survival rates are approxi-
and this was significantly longer than the MST of 26 days for dogs mately 30% to 40%, 10% to 30%, and less than 5% for patients
with tracheobronchial LN metastasis (N1). 281 In another study, with stage II, stage III, and stage IV disease, respectively. 350
dogs with LN enlargement diagnosed before surgery survived for Inherited cancer syndromes caused by germ-line p53 muta-
a median time of 60 days, whereas dogs without LN enlargement tions, retinoblastoma (Rb), EGFR, and other genes have been
had a MST of 285 days. 373 A similar finding was noted in a more reported to increase the risk of lung cancer. Furthermore, asso-
recent study where dogs with lymphadenomegaly had MSTs of ciations between single-nucleotide polymorphism variations have
126 days versus a MST that had not been reached in the dogs been linked to lung carcinogenesis and may be associated with
without lymphadenomegaly. 284 In dogs for which a surgical remis- nicotine exposure. DNA synthesis and repair genes may also play a
sion could be achieved, MST is 330 days versus 28 days in dogs role in the development and prognosis of lung cancer. Commonly
that could not be rendered free of visible disease. 373 Although acquired molecular abnormalities in human lung cancer include,