Page 732 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

710 PART IV Specific Malignancies in the Small Animal Patient

However, surgery has been used to treat solitary lymphoma (stage with bone marrow or stem-cell transplant in dogs, although a
I) or solitary extranodal disease. Careful staging is necessary in recognized model in comparative research settings, 355 is still in
its early phases of development and application in clinical vet-
such cases to rule out multicentric involvement before treating
VetBooks.ir local disease. Surgery has also occasionally been applied for pal- erinary practice. 356–359 Because of the high cost, limited acces-
sibility to relatively sophisticated equipment, and management
liative removal of nodes that are mechanical obstructions in drug
resistant settings. requirements, these types of procedures are limited to preliminary
The benefit of surgical removal of the spleen in dogs with mas- investigations at a few centers. Currently, long-term results docu-
sive splenomegaly remains unclear; however, for indolent lympho- menting significantly enhanced efficacy in sufficient numbers of
mas confined to the spleen, long-term survival after splenectomy is treated cases have yet to be presented.
the norm. 100,102,339,340 In an older report, 16 dogs with lymphoma
underwent splenectomy to remove a massively enlarged spleen and Treatment of Extranodal Lymphoma
were subsequently treated with chemotherapy. 340 Within 6 weeks
of splenectomy, five of the 16 dogs died of disseminated intravas- In general, the veterinary literature contains little information on
cular coagulation (DIC) and sepsis. The remaining 11 dogs (66%) treating various extranodal forms of lymphoma in dogs, and our
had a CR, and seven dogs had a MST of 14 months. No staging or ability to predict outcome is thus limited. In general, it is recom-
histologic information was provided, so the information appears mended that, after extensive staging, in those cases where disease
of limited usefulness, although those with follow-up lived approxi- is shown to be localized to a solitary site, local therapies (e.g., sur-
mately 1 year. In two reports of indolent nodular lymphoma of the gery, local RT) can be used while withholding systemic therapies
spleen (MZL and mantle cell lymphoma [MCL]), outcome was (i.e., chemotherapy) until systemic progression or recurrence is
available on seven MZL cases, including three cases that did not documented. In contrast, if multiple extranodal sites are involved
receive adjuvant chemotherapy after surgery, 100,102 and only one or they are part of a more generalized process, systemic chemo-
died of lymphoma after splenectomy. In a recent report of indolent therapy should be chosen.
lymphomas, four splenic lymphomas (three MZL and one MCL)
underwent splenectomy alone and all survived more than 1 year, Alimentary Lymphoma
with none dying of their primary disease. 101 In another report of Most dogs with alimentary lymphoma are presented with diffuse
41 dogs undergoing splenectomy for lymphoma, those dogs with involvement of the intestinal tract, and involvement of local LNs
indolent forms enjoyed long-term survival. 339 Splenectomy should and liver is common. Chemotherapy in dogs with diffuse interme-
be considered if the lymphoma is not documented in other sites diate- or high-grade disease has been reported to be unrewarding
after thorough staging, if lymphoma is an indolent form, or if for the most part 61,126,360,361 with MSTs of only a few months
splenic rupture has occurred. Of note, no control population con- after CHOP-based chemotherapy; however, durable remissions
sisting of dogs that did not undergo splenectomy exists, so the in a small subset of cases have been reported. A small-cell T-cell
natural history of indolent splenic lymphoma remains uncertain. intestinal lymphoma has been reported in dogs that appears to
have a more indolent course similar to small-cell T-cell intestinal
Radiation Therapy lymphoma in cats. 64,125 In reports of 17 and 20 dogs, MSTs after
Radiation therapy, although of limited routine use in the treat- receiving conservative treatment (prednisone and chlorambucil
ment of lymphoma, may be indicated in selected cases. 341–351 most commonly) were 1.5 to 2.0 years. 64,125 Solitary alimentary
Potential indications are as follows: lymphoma is rare in the dog; however, if the tumor is localized
1. Curative intent therapy for stage I LN and solitary extranodal and can be surgically removed, results (with or without follow-up
disease (i.e., nasal, cutaneous, spinal lymphoma) chemotherapy) can be encouraging. Colorectal lymphoma, gener-
2. Palliation for local disease (e.g., mandibular lymphadenopathy, ally a high-grade B-cell phenotype, is also associated with an indo-
rectal lymphoma, mediastinal lymphoma where precaval syn- lent outcome with median progression-free and overall survival
drome is present, localized bone involvement) times greater than 3 years after initiation of chemotherapy. 362,363
3. Total body radiation combined with bone marrow or stem cell
reconstitution Primary Central Nervous System Lymphoma
4. Whole or staged half-body RT after chemotherapy-induced CNS lymphoma in dogs usually results from extension of mul-
remissions ticentric lymphoma; however, primary CNS lymphoma has
In the latter case, staged half-body irradiation sandwiched been reported. 87,133,135,136,364 If tumors are localized (rare), local
between chemotherapy cycles or after attainment of remission by RT should be considered. Few studies have reported the use of
induction chemotherapy has been preliminarily investigated as a chemotherapy. In one study, cytosine arabinoside (Ara-C) at a
form of consolidation or maintenance. 261,344,345,349,352–354 RT is dosage of 20 mg/m was given intrathecally; this treatment was
2
delivered to either the cranial or caudal half of the body in 4 to 8 combined with systemic chemotherapy and CNS RT. 133 Overall,
Gy fractions and, after a 2- or 4-week rest, the other half of the the response rates are low and of short duration (several weeks to
body is irradiated in a similar fashion. Although these preliminary months), although occasional durable responses are encountered.
investigations were not randomized, they suggest that RT applied
when dogs are in either complete or partial remission is safe and Cutaneous Lymphoma
warrants further investigation to determine whether significant The cutaneous lymphomas represent an assorted group of
therapeutic gain can be realized. A pilot study of low-dose (1 Gy) clinical entities that vary considerably in presentation and
single-fraction total body irradiation in seven dogs with relapsed outcome. 71,74,77,119,129,130,365,366 Epitheliotropic cutaneous lym-
drug-resistant lymphoma, although safely applied, resulted in phoma is most common and has been categorized into two clinically
only partial nondurable (1–4 week) remissions. 341 separate entities (mucocutaneous and cutaneous) based on outcome
Total body irradiation (and/or ablative chemotherapy) for com- differences, with the mucocutaneous form appearing to have better
129
plete or partial bone marrow ablation followed by reconstitution overall outcomes. Treatment of cutaneous and mucocutaneous