Page 245 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

224 PART III Therapeutic Modalities for the Cancer Patient

total body irradiation (TBI) followed by either autologous or diets and regional hygiene are recommended. Steroid enemas
allogeneic transplantation of peripheral blood hematopoietic seem beneficial in some patients with colitis. 243 Late effects from
RT to the pelvic region can occur, and these can be clinically sig-
progenitor cells. After consolidation with a standard CHOP-
VetBooks.ir based chemotherapy protocol, dogs are given a high-dose nificant. This can be addressed by administering the radiation in
75
cyclophosphamide, followed 2 weeks later with progenitor cell
smaller doses per fraction.
75
mobilization using 5 days of recombinant human granulocyte Because of the rapid drop-off between tumor dose and regional
colony-stimulating factor. Peripheral blood mononuclear cells tissues, SRT has introduced treatment to a much wider variety of
are then harvested, and the CD34+ cells are enumerated, with tumors in the thorax and abdomen. Nine dogs with canine adre-
6
the goal of obtaining >2 x 10 /kg CD34+ cells. The next day, nocortical tumors with vascular invasion were treated with SRT
10 to 12 Gy of TBI is administered over 2 days, and the har- (VMAT). The overall MST was 1030 days with minimal toxicity.
vested cells are immediately infused intravenously once RT is The endocrine panels in two of three dogs with cortisol- secreting
11
completed. In a toxicity study of 10 dogs, all dogs experienced tumors normalized. SRT has been used to treat extensive abdom-
grade IV neutropenia, lymphopenia, and thrombocytope- inal LN involvement in dogs with AGASACA, and this was well
nia. 236,237 Neutrophils recovered to at least 500/uL by day 12; tolerated and provided durable palliation in three dogs (personal
however, thrombocytopenia often persisted for weeks. Using communication, Dr. Tiffany Martin). SRT was used to treat six
this treatment strategy, the median DFI and MST were 271 dogs with heart base tumors. 244 The MST was not reached, and
days and 463 days, respectively, for 24 dogs with high-grade four dogs were progression free at 408, 451, 751, and 723 days
B-cell lymphoma, with 33% of dogs living >2 years. When posttreatment. Treatment-related complications included cough-
using the same protocol to treat 13 dogs with high-grade T-cell ing, congestive heart failure, and tachyarrhythmias. 244 Palliative
lymphoma in first remission, the median DFI and MST were RT can be useful for tumors causing airway, bowel, or urinary
184 and 240 days, respectively, with 15% of dogs being long- tract obstruction or neurologic dysfunction. Mediastinal lym-
term survivors. 237,238 phoma often responds rapidly to irradiation. Relief from respira-
tory distress can be achieved within hours of a single dose of RT.
Other Tumors
References
RT is used for a variety of tumors in the thoracic and abdomi-
nal cavities. The principles of patient selection for RT with 1. Coutard H: Roentgen therapy of epitheliomas of the tonsillar
tumors in these regions are the same as for any other region. region, hypopharynx and larynx from 1920 to 1926, Am J Roent-
RT should be considered for any tumor that cannot be excised genol 28:313–331, 1932.
completely. In one study, dogs with thyroid carcinomas treated 2. Pommer A: X-ray therapy in veterinary medicine. In Brandly CA,
with 48 Gy delivered in 4 Gy fractions had PFS rates of 80% Jungher EL, editors: Advances in veterinary science, Academic Press,
at 1 year and 72% at 3 years. 239 Thymomas are radiation 1958, pp 98–136.
responsive in human patients. 240 In a study of seven cats with 3. Withers HR: The four R’s of radiotherapy, Adv Radiat Biol 5:241–
thymoma treated with RT, the MST was close to 2 years (see 271, 1975.
Chapter 34, Section B). 241 4. DeVita Jr VT: Progress in cancer management, Keynote address,
Cancer 51:2401–2409, 1983.
Eighteen dogs with primary disease of the urinary bladder (7), ure- 5. Farrelly J, McEntee MC: A survey of veterinary radiation facilities
thra (1), or prostate (10) were treated with IMRT assisted by image in 2010, Vet Radiol Ultrasound 55:638–643, 2014.
guidance to verify tumor position. In all dogs, the radiation dose 6. Gieger T: Veterinary radiation facilities. Available at: https://
124
ranged from 54 to 58 Gy, delivered in 20 daily fractions. The majority vetcancersociety.org/vcs-members/links-of-interest-2/radiation-
of patients were treated with adjuvant chemotherapy and non-steroid facilities/.
antiinflammatory drugs (NSAIDs). Acute and late tissue toxicities 7. Geiger T: ACVR website.approved veterinary radiation oncol-
were limited, and treatment was well tolerated. The overall MST was ogy residency programs. Available at: https://www.acvr.org/page/
654 days. Location of the primary tumor had no effect on either local approved-radiation-oncology-residency-programs.
tumor control or survival. A modified treatment protocol in a larger 8. Griffin LR, Nolan MW, Selmic LE, et al.: Stereotactic radiation
number of dogs resulted in increased radiation effects such as urinary therapy for treatment of canine intracranial meningiomas, Vet
Comp Oncol 14:e158–e170, 2016.
incontinence (personal communication, B. Clerc-Renaud). 9. Gieger TL, Nolan MW: Linac-based stereotactic radiation therapy
Perianal adenocarcinomas and apocrine gland anal sac adeno- for canine nonlymphomatous nasal tumours: 29 cases (2013-
carcinomas (AGASACA) (see Chapter 23, Section H) can be dif- 2016), Vet Comp Oncol 16:E68–E75, 2018.
ficult to control locally with surgery alone and may metastasize 10. Nolan MW, Arkans MM, LaVine D, et al.: Pilot study to deter-
to the regional sublumbar LNs. RT may be used in the adjuvant mine the feasibility of radiation therapy for dogs with right atrial
setting to treat residual microscopic or gross locoregional disease. masses and hemorrhagic pericardial effusion, J Vet Cardiol 19:132–
A study of 28 dogs with locoregionally advanced (stage IIIb) 143, 2017.
AGASAC treated with either surgery or RT showed a significantly 11. Dolera M, Malfassi L, Pavesi S, et al.: Volumetric-modulated arc
longer median PFS for dogs treated with IMRT (14.7 months) stereotactic radiotherapy for canine adrenocortical tumours with
compared with dogs treated surgically (6.0 months). 242 Perianal vascular invasion, J Small Anim Pract 57:710–717, 2016.
gland carcinomas are generally slow to disseminate systemically, 12. Zhao P, Lu S, Yang Y, et al.: Three-dimensional conformal radia-
tion therapy of spontaneous benign prostatic hyperplasia in canines,
so full-course RT or SRT of involved regional LNs may be war- Oncol Res 19:225–235, 2011.
ranted. Mucositis also can occur whenever any portion of the ali- 13. Beckmann K, Carrera I, Steffen F, et al.: A newly designed radiation
mentary system is included in the RT field. Colitis is a common therapy protocol in combination with prednisolone as treatment
acute effect during RT for colorectal tumors. Severe large bowel for meningoencephalitis of unknown origin in dogs: a prospective
diarrhea may be seen. Anusitis from irradiation is worsened by pilot study introducing magnetic resonance spectroscopy as moni-
the diarrhea, making the patient quite uncomfortable. High-bulk tor tool, Acta Vet Scand 57(4), 2015.