Page 818 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

796 PART IV Specific Malignancies in the Small Animal Patient

Treatment and Prognosis

VetBooks.ir The clinical course of disseminated HS, if left untreated, is rapid
and usually fatal, whereas the localized form may be more slowly
480
Few reports documenting survival duration after
progressive.
surgical excision of localized HS exist. However, in a series of 18
PAHS confirmed with CD18 staining, the MST for dogs undergo-
ing amputation was 6 months and the metastatic rate was 91%. 538
Interestingly, the periarticular form of HS may be associated with
a better prognosis than that at other locations. In one study, dogs
with PAHS lived significantly longer than did dogs with non-
PAHS, with overall MSTs of 391 and 128 days, respectively, 559
despite the presence of suspected metastasis at diagnosis in 13 of
19 dogs with PAHS. Still, dogs with PAHS with no evidence of
metastasis at diagnosis (MST 980 days) lived significantly longer
than those with evidence of metastasis (MST 253 days). 559 Pro-
20 m longed survival has also been reported in dogs with localized HS
in other anatomic sites treated with local and systemic therapy,
• Fig. 34.15 Cytology of histiocytic sarcoma in the bone marrow of a dog. however. 560 Thus it is not clear whether PAHS has a better prog-
Neoplastic cells (arrows) and erythroid progenitors (arrowheads) are vis- nosis owing to its more localized nature or due to an inherent
ible. Note phagocytic activity of neoplastic cells. (Wright-Giemsa, 100× difference in clinical behavior.
objective.) (Courtesy Elizabeth Little, VMD, DACVP, IDEXX Laboratories, CCNU appears to be the most effective chemotherapy agent
Langhorne, PA.)
against HS in dogs. One study reported a 46% response rate to
CCNU in 56 dogs with gross measurable disease with a median
Because HS is multifocal or disseminated in most dogs, com- remission duration of 85 days. The MST of responders was 172
plete staging is recommended. Complete blood count and bio- days compared with 60 days in nonresponders. 542 In this study,
chemical screens may be abnormal in dogs with disseminated or anemia, thrombocytopenia, hypoalbuminemia, and splenic
HHS. 480,483,542 Anemia is common and usually regenerative when involvement, all factors associated with the hemophagocytic
caused by erythrophagocytosis by neoplastic cells. Leukocytosis, subtype of HS, were associated with a grave prognosis. Cortico-
thrombocytopenia, increased liver enzymes, hypoalbuminemia, steroids did not improve response to therapy in this study. In a
and hypocholesterolemia are frequent findings, and hypercalcemia prospective study of 21 dogs with HS treated with 90 mg/m of
2
occurs occasionally. 542 HS was the second most common cause CCNU, the response rate was lower at 29%, though 67% of dogs
of pancytopenia in dogs in a retrospective study of 51 dogs at a received only one dose of CCNU. 561 The median response dura-
veterinary teaching hospital. 551 Hyperferritinemia has also been tion was 96 days. CCNU therapy used as an adjuvant to surgery
documented in dogs with HS and is theorized to be result of fer- and/or RT RT may result in lengthy survival times in dogs with
ritin production by tumor cells. 552,553 Eighty-nine percent of dogs localized HS. One retrospective study documented an MST of
with HS had hyperferritinemia in one study, although IMHA, 19 months in 16 dogs with localized HS treated with aggressive
liver disease, and lymphoma were also associated with high rates of combination therapy. 560
hyperferritinemia. 553 A recent study attempting to screen healthy CCNU has also been studied in combination with DOX to
BMDs for early HS found that serum ferritin may serve as a treat HS, and when administered in an alternating fashion every 2
potential marker of the disease. High ferritin levels were common weeks, the response rate was 58% with a median time to progres-
in dogs with clinical HS, but only 2 of 5 dogs with early HS had sion of 185 days. 562 Dacarbazine has been studied in the rescue
high ferritin levels, suggesting that further study is necessary to setting for HS and was associated with a response rate of 18%,
explore the utility of ferritin as a screening test for BMDs. 554 with an event-free survival time in responders of 70 days. 563 The
Thoracic radiography and abdominal ultrasonography com- efficacy of epirubicin against HS has also been studied and was
monly reveal abnormalities. 542 Pulmonary involvement may associated with a response rate of 29%. 564
appear as a diffuse interstitial infiltrate, patchy consolidated areas, Individual reports of responses to liposomal DOX and pacli-
or focal or multifocal mass lesions. The right middle lung lobe is taxel chemotherapy also exist. 565,566 In addition, a case report of a
the most common pulmonary location for HS and internal air dog with cutaneous disseminated HS described temporary remis-
bronchograms are commonly seen. 555,556 Radiographic evidence sions resulting from multiple treatments including cyclophos-
of sternal, cranial mediastinal, and/or tracheobronchial lymph- phamide, vincristine, prednisone, mitoxantrone, dacarbazine,
adenopathy may also be noted. Hepatosplenomegaly, splenic or and etoposide. 567 Studies of metronomic chemotherapy targeting
hepatic mottling, or discrete nodules or masses in these organs are angiogenesis and the immune environment have also included
the most common abdominal ultrasonographic abnormalities. 557 dogs with HS. Responses to metronomic lomustine and chloram-
Bone marrow aspiration cytology may reveal tumor infiltrate, bucil have both been reported. 568,569 The bisphosponate clodro-
especially in patients with cytopenias. In addition, flow cytom- nate has been studied in histiocytic cell lines and in five dogs with
etry has been used to differentiate etiology of hemophagocytosis HS. 570 Two of the five dogs treated with a liposomal formulation
in bone marrow samples containing more than 5% macrophages of clodronate experienced tumor regression and further study is
and cytologic evidence of hemophagocytosis. 558 Results suggested warranted.
that cellular distribution in scatter plots and number of histio- The efficacy of RT against HS has not been fully studied; how-
cytes may help differentiate neoplastic from nonneoplastic causes ever, preliminary evidence suggests that HS is radioresponsive. In
of hemophagocytosis. a report of 37 FCR with mostly PAHS, dogs undergoing RT lived