RADIOTHERAPY WITH AND WITHOUT CHEMOTHERAPY FOR LOCALIZED LYMPHOMA IN 10 CATS

A retrospective study was undertaken to determine the efficacy of radiotherapy with and without chemotherapy for treatment of localized lymphoma in 10 cats. Tumor location included nasal cavity (3 cats), retrobulbar area (3 cats), mediastinum (1 cat), subcutaneous tissue (1 cat), maxilla (1 cat) and mandible (1 cat). Six cats were treated with radiation alone and 4 cats also received chemotherapy during and/or after radiotherapy. Complete remission was achieved locally in 8 of 10 cats, whereas 2 cats had partial remission. Five of the 6 cats treated with radiotherapy alone achieved complete remission. Overall mean and median remission times for the 8 cats with complete remission were 123 weeks and 114 weeks, respectively (range 4 to 277 weeks). Three of the 8 cats have been in complete remission for more than 131 weeks and are still alive. Three cats achieving complete local remission developed lymphoma outside the radiation field. One cat had recurrence at the site of irradiation. Results of the retrospective study suggest that radiotherapy with and without chemotherapy may be effective for the treatment of localized lymphoma in the cat.     

HEMOPOIETIC RESPONSES OF THE CAT TO TOTAL BODY IRRADIATION FOLLOWED BY CHEMOTHERAPY

Cats with lymphosarcoma are affected with rapidly progressive, fatal neoplasia of hemopoietic tissues. The very aggressive nature of this type of neoplasia requires intense therapy, which in most instances is only palliative. A combination of total body irradiation and cytotoxic chemotherapy in four normal cats was followed by similar patterns of leukopenia and throm-bocytopenia in all cats. The radiation protocol and the complications of the transient throm-bocytopenia and leukopenia are discussed and compared with reports of similar efforts in human medicine. The responses from these normal cats were quite similar to those seen in humans undergoing similar therapy. The cat may be considered as a possible model for further radiotherapy research.     

COMPUTED TOMOGRAPHY OF THE NORMAL FELINE NASAL CAVITY AND PARANASAL SINUSES

Computed tomography (CT) images of the feline nasal cavity and paranasal were acquiredfrom noraml adult cats. Good resolutin and amatomic detail were obtained from the CT images using soft tissue formatting. A desciption of normal feline nasal cavity and paranasal sinus anatomy using CT is presented.     

ULTRASONOGRAPHIC APPEARANCE OF FELINE ALIMENTARY LYMPHOMA

Abdominal ultrasonography was performed in seven cats with intestinal lymphoma and four cats with gastric lymphoma. Ultrasonographic abnormalities included the presence of a hypoechoic mass associated with the gastrointestinal tract, focal or diffuse thickening of the gastric wall, symmetric thickening of the bowel wall, loss of the normal layered appearance of the gastrointestinal wall, and abdominal lymphadenopathy. The thickness of the stomach wall ranged from 8 to 22 mm in cats with gastric lymphoma, and the thickness of the bowel wall ranged from 5 to 20 mm in cats with intestinal lymphoma. Fine needle aspiration of a gastrointestinal lesion was performed without complication in six cats, and was diagnostic for lymphoma in five out of six. Results of this study indicate that ultrasonography is an effective noninvasive means of identifying lesions consistent with alimentary lymphoma in cats.     

RESPONSE OF NINETEEN CATS WITH NASAL LYMPHOMA TO RADIATION THERAPY AND CHEMOTHERAPY

The records of 19 cats treated for stage I nasal lymphoma with radiation therapy and chemotherapy were reviewed to determine response to therapy, treatment outcome and possible prognostic indicators. All cats were treated with megavoltage radiation therapy to a total dose ranging from 22 to 48 Gy (median dose = 42 Gy). All cats were prescribed at least 6 months of multiagent chemotherapy. The median progression-free interval for all cats was 945 days (31 months). Two cats did not achieve clinical remission. Of 17 cats evaluable for relapse, 10 (58.8%) were progression free during the entire follow-up period. Four cats (23.5%) suffered local recurrence, while three (17.6%) experienced distant relapse. The median survival time was 955 days (31.4 months). The only variable found to have a significant negative impact on survival was destruction of the cribriform plate before therapy (P= 0.002). The long progression free and survival times reported here indicate that cats with stage I nasal lymphoma treated with aggressive local and systemic therapy can have a favorable outcome when compared with other anatomic forms of lymphoma. Despite strong clinical responses to the multimodality therapy used, the fact that three (17.6%) cats relapsed distantly supports the recommendation that treatment with radiation therapy alone is insufficient until further prospective studies can be performed.     

M-MODE ECHOCARDIOGRAPHY AS A DIAGNOSTIC AID FOR FELINE CARDIOMYOPATHY

Normal cats and cats with congestive cardiomyopathy (CCM) and hypertrophic cardiomyopathy (HCM) were examined using M-mode echocardiography to determine its diagnostic capabilities. Sixteen normal cats were examined to verify previously reported data and to add further echocardiographic inforamtion (left atrial/aortic root ratio, left posterior wall thickness at end systole and end diastole, amplitude of mitral valve excursions, and velocity of valve opening and closure) to aid in differential diagnosis. Significant (p<0.05) changes were detected between the normal cats and those with cardiomyopathy. In each type of cardiomyopathy, alterations in left atrial dimension, left atrial/aortic root ratio, left ventricular dimension, left ventricular wall thickness and percentage of ventricular dimensional change were identified. Altered mitral valve motion was found with HCM. Echocardiography was found to be an accurate technique for definitive diagnosis of feline cardiomyopathy.     

PROTON IRRADIATION OF FELINE NASAL PLANUM SQUAMOUS CELL CARCINOMAS USING AN ACCELERATED PROTOCOL

Fifteen cats were treated for squamous cell carcinoma of the nasal planum using proton beam radiation. The protocol used was accelerated with eight equal fractions given on four consecutive days, with a minimum of six hours between fractions. Total dose of radiation delivered was escalated with nine cats receiving 40.4 CGE (60Co Gy equivalent), and three cats each receiving 42.4 and 44.8 CGE. Complete response to the protocol was 60% (9/15), partial response was 33% (5 of 15), and no response was seen in 6.6% (1 of 15). Tumor control rate at one year was 64% and no cat had tumor recurrence after one year. Median survival was 946 days (+/- 516 days). Side effects were minimal with no severe reactions noted in the early or late period. This protocol offers an effective treatment for squamous cell carcinoma of the feline nasal planum with minimal side effects and may be adaptable to conventional radiation sources particularly when the field size is very small.     

EVALUATION OF LYMPHOMA IN A CAT USING 99mTc-SESTAMIBI

This report describes the evaluation of cutaneous lymphoma in a cat using 99mTc-sestamibi. A mass in the left pes with extension to the left popliteal lymph node was diagnosed as B-cell lymphoma. Thoracic and abdominal radiography and abdominal ultrasound were unremarkable. Scintigraphy using 99mTc-sestamibi confirmed the lesion was confined to the left hind leg, and the leg was amputated. The cat made a full recovery.     

FELINE HYPERTHYROIDISM: EFFICACY OF TREATMENT USING VOLUMETRIC ANALYSIS FOR RADIOIODINE DOSE CALCULATION

Hyperthyroidism was diagnosed in 80 cats with thyroid scintigraphy using technetium pertechnetate. These cats were subsequently treated with radioiodine using a modified fixed dose method based on the volume of hyperfunctioning thyroid tissue calculated from the pertechnetate scans. The medical records and thyroid scintigrams were evaluated retrospectively. Follow-up was obtained on the cats to evaluate treatment success. Several parameters were evaluated in an attempt to identify a difference between treatment success and failure. Cats that failed to become euthyroid after one dose of radioiodine had a significantly higher pretreatment serum thyroxine level, had a significantly larger volume of hyperfunctioning thyroid tissue on scintigrams, and cats receiving oral versus intravenous radioiodine were over represented. Based on our results we conclude: 1) the administration of a dose of radioiodine based solely on the volume of hyperfunctioning thyroid tissue as estimated from the pertechnetate scan may be inadequate for those patients with extremely elevated serum thyroxine levels or large thyroid glands, and 2) oral administration of radioiodine is not recommended for the treatment of feline hyperthyroidism.     

USE OF 3'-DEOXY-3'-[18F]FLUOROTHYMIDINE PET/CT FOR EVALUATING RESPONSE TO CYTOTOXIC CHEMOTHERAPY IN DOGS WITH NON-HODGKIN'S LYMPHOMA

Imaging and measurement of proliferation with computed tomography (CT) and positron emission tomography (PET) provide a noninvasive method for improved staging and monitoring of response to cancer treatment. We evaluated prospectively the proliferation marker 3'-deoxy-3'[¹⁸F] fluorothymidine (FLT) in the context of FLT-PET/CT for detection of early response, confirmation of posttreatment response, and prediction of relapse in dogs with non-Hodgkin's lymphoma. Nine dogs with non-Hodgkin's lymphoma who were scheduled to receive five cycles of an investigational cytotoxic chemotherapy agent were included. All dogs received baseline FLT-PET/CT imaging immediately before chemotherapy. Intent was to repeat imaging with FLT-PET/CT at various time points: group 1 ( n =4), 5 days after initiation of chemotherapy and 3 weeks following the last chemotherapy administration; group 2 ( n =5), before the fourth cycle of chemotherapy and 3 weeks following the last administration. Two dogs in group 2 did not undergo repeat PET/CT. Body mass standardized uptake values (SUV) for FLT were calculated for each dog. Eight dogs had initially increased FLT uptake (mean SUV_max=9.8 [2.6–22.3]). Mean SUV decreased significantly for the seven dogs that underwent follow-up PET/CT following chemotherapy (mean SUV_max=3.5 [1.1–7.9], P <0.016). Increased uptake preceded clinical and cytological evidence of relapse in two dogs. Ki-67 immunohistochemistry confirmed decreased proliferation corresponding to decreased SUV in three canine lymph node samples. FLT-PET/CT functional and anatomical imaging shows promise for the evaluation of response to cytotoxic chemotherapy in dogs with non-Hodgkin's lymphoma and for predicting relapse before standard clinical and clinicopathologic confirmation.     

DIAGNOSTIC ACCURACY OF GRAY‐SCALE ULTRASONOGRAPHY FOR THE DETECTION OF HEPATIC AND SPLENIC LYMPHOMA IN DOGS

Gray‐scale ultrasonography is often used to screen for involvement of the liver and spleen in canine lymphoma patients but the utility of sonography for staging lymphoma has not been evaluated quantitatively. We performed abdominal sonography in 28 dogs with a confirmed diagnosis of lymphoma. Needle aspirates were obtained for cytology from three separate sites in the liver and three sites in the spleen and the sonographic appearance was noted at each site. Our hypothesis was that in dogs newly diagnosed with lymphoma, abnormal appearance of the liver or spleen on ultrasound examination is an indication that lymphoma is present in that organ. Cytologic evaluation was used as the gold standard. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of hepatic and splenic abnormalities seen on ultrasound for diagnosis of lymphoma were 72.7%, 80.6%, 77.4%, 76.3%, and 76.8% for the liver, respectively, and 100%, 23.3%, 64.6%, 100%, and 68.1% for the spleen, respectively. Based on these results, we recommend that aspirates be performed for detection of lymphoma in the spleen of dogs only when the spleen appears abnormal ultrasonographically and that cytology of the liver be performed, regardless of ultrasonographic appearance, to determine the presence or absence of lymphoma.     

RECEIVER OPERATING CHARACTERISTIC CURVE ANALYSIS OF THE UTILITY OF THORACIC RADIOGRAPHS FOR THE DIAGNOSIS OF FELINE CARDIAC DISEASE

The results of a retrospective study in which 90 sets of feline thoracic radiographs were examined by six readers were evaluated with the aid of receiver operating characteristic (ROC) curve analysis. There were 51 sets of radiographs of 45 normal cats and 39 sets of radiographs of 33 cats with cardiac disease. The readers were asked to classify each set of radiographs as normal or abnormal, with respect to cardiac disease, into one of five diagnostic cholces that reflected reader confidence. The method of generating an ROC curve is discussed. There was no significant difference in the accuracy of interpretation between the five experienced readers. The mean accuracy of this group was 91%. However, inspection of the individual ROC curves demonstrated a fundamental difference in underlying reader bias (i.e., over-or underreading). As expected, the experienced readers were statistically more accurate than an inexperienced reader. ROC curve methodology has potential applications in veterinary medicine not only for assessing observer performance and reader bias, but also for comparing tests and in clinical decision making.