Page 1425 - Clinical Small Animal Internal Medicine

155 Mast Cell Neoplasia 1363

(a) (b)
VetBooks.ir

Figure 155.4 (a) A female mixed‐breed dog at initial presentation with a MCT of the medial aspect of the upper eyelid. Enucleation of
the eye was initially recommended. (b) The same patient after one month of tyrosine kinase therapy. Surgical margins were achieved
with aggressive local excision without enucleation.

Either surgical removal or radiation of the draining Table 155.1 CVP combination protocol as initially noted
lymph nodes should be considered for cases where in Rassnick et al.
regional node metastasis is confirmed (stage III).
There are a variety of chemotherapy treatment Week Protocol
options for a MCT. The European consensus state- 2
ment on MCTs indicates that chemotherapy is used to Week 1 Prednisone 2 mg/kg/day Lomustine 70 mg/m PO
treat metastatic disease to either regional lymph nodes Week 3 Prednisone 1 mg/kg/day †
2
or distantly; when radiation or surgery are not available Vinblastine 3.5 mg/m IV
or possible; and as a neoadjuvant to reduce tumor bur- Week 5 Prednisone 1 mg/kg every other day until week 24
2
den prior to more traditional surgery or radiation. It is Lomustine 70 mg/m PO
2
important to understand that chemotherapy does not Week 7 Vinblastine 3.5 mg/m IV
offer the same curative results as radiation or surgery Week 9 Lomustine 70 mg/m PO
2
and should not be used as a convenient alternative to Week 12 Vinblastine 3.5 mg/m IV
2
these modalities. Week 15 Lomustine 70 mg/m PO
2
Prednisone has the longest history of use against 2
MCTs. It is unclear if the effects of prednisone are truly Week 18 Vinblastine 3.5 mg/m IV
2
cytotoxic or simply aid in reducing peritumoral edema Week 21 Lomustine 70 mg/m PO
2
and inflammation secondary to histamine release. A Week 24 Vinblastine 3.5 mg/m IV
popular theory suggests that glucocorticoids block stem Taper off prednisone over 4 weeks
cell factor release from regional epithelial cells and fibro- IV, intravenous; PO, by mouth (per os).
blasts. Stem cell factor is a known activating protein of
the KIT pathway which is often mutated in MCTs.
Antiinflammatory dosing of prednisone at 1 mg/kg/day
is considered sufficient for MCTs. Immunosuppressive Table 155.2 Alternating lomustine and vinblastine protocol
doses have not been found to be more effective and only as initially noted in Cooper et al.
increase the risk and severity of prednisone‐induced
side‐effects. Week Protocol
Traditional chemotherapy options include the vinca 2
alkaloids vinblastine and vinorelbine, the alkylating Week 1 Lomustine 60 mg/m PO
2
agent lomustine, and a taxane, paclitaxel. Both lomustine Week 3 Vinblastine 2.0 mg/m IV
and vinblastine have an overall response rate of 40–50%. Repeat for 4‐6 cycles
Recently, the drugs were combined with prednisone pending response
(Tables 155.1 and 155.2) and achieved an overall response IV, intravenous; PO, by mouth (per os).