X-ray tvt

X-ray for the Transmissible Venereal Tumor

Author: Dr Sovereign Martin
University specialist in Oncología. Roffo institute, UBA Technical Director of the Center of X-ray for Animals of Buenos Aires (CRABA).
to msoberano@fvet.uba.ar

Summary
The transmissible venereal tumor (TVT) is implants of tumorlike cells of cariotipo altered. This tumor is transmitted by means of the sex or by social conducts between the canine ones (licked and sniffing, among others).
Its greater incidence is observed in animals between 4 and 5 years, and in the canine ones of great stature (greater of 18 kilos). Racial predisposition does not exist and the number of ill females surpasses to the one of the males.
The definitive diagnosis is made by means of a biopsy, but the punción with fine needle or one impronta, allows to define to the tumor through their cytological study.
The treatments used for the TVT are: the surgery, the x-ray and the chemotherapy.
The surgery is not a treatment of election for the treatment of the venereal tumor. The rate of recurrence posoperatoria is high (30-70%).
The chemotherapy is an effective sistémica therapy for the TVT. Desvantajas of this treatment is: its sistémicos collateral effects (13%), its indication for a tumor of local behavior, the state of health and the ages of the patients in treatment.
The x-ray allows the ?cure? of the tumor. An only 10 dose of Gy obtains a 100% of control of the disease.
The treated weave is: only tumorlike and its margins; collateral effects are not observed associate the treatment.
Key words: x-ray, tumor, venereal disease, canine.

Abstracts
Venereal Transmissible tumor (TVT) is to transplantable malignant neoplasm that there are to different cariotype. This tumor is readily transmitted during coitus by to transfer of cells from diseased to healthy dogs, but it also may spread by social behavior (licking or sniffing). The average age of dogs 4 with 5 TVT is to years and most dogs trend to be to larger breeds (weighing dwells than 18kg). Nonracial There is predisposition and female dogs presented plows to higher than male ones. Definitive diagnosis is made by biopsy, but cytologic preparations from fine-needle aspiration or impression smears from the tumor surface characterize TVT. For Treatment modalities TVT plows: surgery, chemotherapy and radiation therapy. For Surgery is not considered an effective treatment this disease. There plows high rates of post-surgery recurrence (30-70%). Chemotherapy is an effective, sistemic modality of treatment. The incidence of side effects (most commonly vomiting and neutropenia) was 13%. Canine TVT is responsive to radiation therapy; 100% ?obtained cures? is with to single therapeutic dose of 10 Gy ace long ace metastasis there are not occured. Only the target volume is treated and not side effects were observed. Key words: radiation therapy, tumor, venereal, canine.

Introduction
The transmissible venereal tumor (TVT) is scattered during the sex by means of implants cellular between the ill and healthy animals. Also it is transmitted by the social conducts between young animals, in reproductive stage. It affects any race, although the animals of greater of 18-20kg, and the females are most susceptible of I infect. (1) the age average of appearance is between the 4 and 5 years. This tumor appears anywhere in the world and the affected zones more are the urban ones, of tropical and subtropical climate, with times of seasonal rains.
The origin of the TVT is not known, although the inmunohistoquímica studies determined the reticuloendotelial component of their cells. The cells have a number of 59+/-5 chromosomes, unlike the 78 chromosomes of the canine one. This genetic pattern stays constant anywhere in the world .(2) the TVT appears as a firm, soft or coldable mass with tendency to ulcerar themselves and to bleed.
He is located generally in the external genitals of the canine ones. Other places of appearance are the external mucous, such as those of the nasal cavity, the oral mucosa and the conjuntival, among others. Its growth is local and the rate of metástasis of this tumor is of 1.5 - 6%, in experimental cases of cellular transplant, and of the 0-17% in the cases derived to reference centers.
The sites of more common metástasis are the regional linfonódulos, thus also the skin and the subcutaneous one.
The definitive diagnosis we made it by means of a biopsy, but a cytological study by superficial punción or hisopado of the tumor, also can be used. The animal must be evaluated clinically and must be made necessary the complementary studies for its correct estadificación.

External x-ray for the Transmissible Venereal Tumor
The x-ray is the use of ionizing radiations for the local treatment of the cancer. Its indication varies according to the histológico type of the tumor, being the tumors of round cells (linfoma, mastocitoma, histiocitoma, TVT) very sensible to rays.
In general, the TVT has a local growth in the canine genital apparatus and the rate of metástasis is low. Then, by its radiosensitivity and its form of growth located to the reproductive apparatus, the x-ray is useful for the treatment of this pathology.
The animal is positioned in agreement the site of the injury and the treatment field is defined.
The necessary dose for the 10 TVT is of Gy. With the size of the field to radiate (cm.) and necessary the total dose (Gy.) we will be able to calculate the total time of treatment.
He is useful to clarify that the total dose is applied a single time, that is to say, in a treatment session.
The answer is of the 100%. (4-5) In the canine females the correct positioning of the animal is necessary. This is important for the bearing of the field to treat, due to the internal location of the tumor (VER FOTO.Leyenda: the female is placed lateral position.
The mass is felt via vaginal and the treatment field is defined, that is to say, the tumor and its margins. The rays cross the superficial structures and reach the center of the field). Once carried out the treatment, the changes in the tumor begin to be observed (TO SEE PHOTOS SERIADAS).
When finalizing the time of treatment, we can notice intratumorlike zones of hemorrhage, as well as, light eritema and increase of the bled one. The rays act in the later days to the treatment, of two different ways: direct on the tumorlike DNA and a other hint, by means of the formation of free radicals with the water and the oxygen of the weave.
The complete answer is observed the 20 days of the treatment. This last one stays in the time without detecting metástasis. Collateral effects in the treated animals are not observed. An increase of the signs due to the tumorlike necrosis caused by rays exists after session.
In the case of the females, by the internal location of the TVT, reversible alopecias in the radiated field were observed (perianal zone). In no case it was necessary symptomatic therapy by upheavals caused by the treatment. This is due to: a single dose allows the repair of the damage caused by the received dose, the region to treat is readily accessible and it is remote of weaves of greater radiosensitivity (bony marrow, lung), and finally, the status performance of the treated animals is optimal (young, without concurrent sistémicos upheavals).
Discussion
The treatments available for the TVT are varied, among them are: the surgery, the chemotherapy and the radiotarapia.
The surgery was made in 35 dogs with primary injuries or metastásicas (nongenital) .(3) Of the 23 canine ones with unique genital injuries, the tumor resorted in 4 dogs (locally in one and other sites in 3).
The time passed, from the moment of the surgery to the relapse, was of 6 months. There was recurrence in 7 of the 12 dogs with extragenital injuries. The rate of recurrence in this work was of 33.4%. In other works, the rate of recurrence posoperatoria is greater of 68%.(6)
The surgery is not an effective treatment for this disease (1). Diverse drugs have been you decipher for the treatment of the TVT. Poliquimioterapia and monochemotherapy protocols have been reported.
The used drugs were the following ones: the oral or endovenosa ciclofosfamida one via, the metotrexato, the doxorrubicina and the vincristina (7-8)
Ciclofosfamida (CF) oral and the metotrexato did not have answer, whereas the CF by endovenosa route had a partial answer. Calvert and col. they obtained a 95% of complete answer with the endovenosa infusion of vincristina (VCR), with a 5% of partial answers. To these animals another dose of VCR along with ciclofosfamida was provided to them. Answers were not reported and as rescue treatment were decided on the doxorrubicina, 3 cycles by endovenosa route. Half of the treated animals had a complete answer and the rest did not have answer to the treatment. The author describes a 13% of collateral effects with the vincristina use, like monodrug.
The most frequent toxicities are: the acute gastrointestinales upheavals (vomits), the mielosupresión (neutropenia) and the injuries in the infusion site, by the extrusion of the vincristina.
Conclusion
The habitual handling of the patient with a venereal tumor transmissible era with quimioterápicos drugs. This fact responds a: the good rate of complete answers, the cost of the treatment, the current handling of the drug and the absence of other effective treatments for this organization. In spite of these advantages, the animal is treated in sistémica form for the control of a tumor of local behavior. This fact is important since, in their majority, the patients are young, healthy and in reproductive stage.
The x-ray allows the ?cure? of the tumor without affecting the animal in sistémica form. As well, the use of radiations can be used for the handling of the therapeutic faults: partial answers or nonanswers to other therapies.
The use of the x-ray in the treatment of the TVT allows to cure this pathology in an only session of radiations of 20 minutes (the time varies according to the field to treat). This therapeutic tool will allow to simplify the treatment of the TVT and to reserve the use of the quimioterápicos stops: the cases of TVT with multiple injuries in different points from the organism, metastásicas injuries in internal organs and like neoadjuvant therapy of citoreducción, to mention some examples.

Bibliography
1 - Ogilvie, K; Moore, A. Managing the veterinary cancer patient. Veterinary Learning Systems Co., Inc. Trenton, New Jersey. 1995
2 - Rogers, K.S. venereal Transmissible tumor. In Compendium on Continuing Education. Sept. 1997.
3 - Amber, E.I; Henderson, R.A. transmissible Canine venereal tumor: evaluation of surgical excision of primary and metastatic injury in Zaire Nigeria. JAVMA. 1882:350 - 352, 1982.
4 - Thrall, OF. Orthovoltage radiotherapy of canine transmissible venereal tumor. Vet Radiol.23: 217-219, 1982
5 - Sovereign, M. Radiation therapy for venereal transmissible tumor in a dog. Abstracts of the XXIII Congress of The World Small Animal Veterinary Association. Buenos Aires, Argentina. October 1998
6 - Idowu, A.L. To retrospective evaluation of four methods of treating canine transmissible venereal tumor. J. Small Anim Pract.25: 193-198, 1984
7 - Brown, N. Or; Calvert, C; MacEwen, E.G. Chemotherapeutic management of transmissible venereal tumor in 30 dogs. JAVMA.176: 983-986, 1980.
8 - Calvert, C; Leifer, C.E; MacEwen, E.G. for Vincristine treatment of transmissible venereal tumor in the dog. JAVMA.181: 163-164, 1982.

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