Dacarbazine as single-agent therapy for relapsed lymphoma in dogs

Novel Treatments for Lymphoma

Lymphoma is a common disease in companion animals. While conventional chemotherapy has the potential to induce remission and prolong life, relapse is common and novel treatments are needed to improve outcome. This review discusses recent modifications/adjustments to conventional standard of care therapy for canine and feline lymphoma, options for treatment or relapsed/refractory disease, and cutting-edge immunotherapy and small molecule-based approaches that are in varying stages of regulatory approval.

Review of Canine Lymphoma Treated with Chemotherapy-Outcomes and Prognostic Factors

While canine lymphoma is a relatively common and important disease seen by veterinarians, there are limited comprehensive reviews of the literature regarding the remission and survival times following chemotherapy, and the associated prognostic factors. This comprehensive thematic review covers the available veterinary literature covering treatment outcomes and identified prognostic factors. A lack of standardised approaches to evaluate and report the outcomes was identified, including factors that would alter the duration of responses by weeks, or occasionally months. After publication of the suggested reporting criteria, this has improved but is still not uniformly applied. The prognostic factors included for evaluation varied from as few as three to seventeen, with over 50 studies using only univariate analysis. Individual papers reported much longer outcomes than others, but assessing the outcomes overall, there has been minimal change over the last 40 years. This supports the belief that novel approaches for lymphoma therapy will be required to substantively improve outcomes.

Retrospective evaluation of fresh platelet concentrate administration in dogs: Patient characteristics, outcomes, and transfusion practices in 189 transfusion episodes (2008-2019)

OBJECTIVE

To describe patient characteristics, underlying disease processes, clinical outcomes, transfusion dose and type (therapeutic or prophylactic), platelet count changes, and adverse events associated with platelet concentrate (PC) administration in dogs.

DESIGN

Retrospective study.

SETTING

University teaching hospital.

ANIMALS

A total of 149 dogs, representing 189 PC transfusion episodes.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

In this population, 39 of 149 dogs (26.2%) were diagnosed with primary immune-mediated thrombocytopenia, 22 of 149 (14.8%) had decreased bone marrow production, 12 of 149 (8.0%) received PC during a massive transfusion, 3 of 149 (2.0%) had congenital thrombocytopathia, 59 of 149 (39.6%) had severe thrombocytopenia of other causes, and 14 of 149 (9.4%) underwent transfusion for miscellaneous causes without a documented severe thrombocytopenia. In 117 of 149 dogs (78.5%), >1 site of hemorrhage was noted. The most common sites of hemorrhage were the gastrointestinal (GI) tract in 89 of 149 (59.7%) and the skin in 78 of 149 (52.3%). Overall survival to discharge was 59.1% (88/149). The median PC dose was 0.8 units per 10 kg of body weight per transfusion episode (range: 0.2-6.7). Of 189 episodes, 29 of 189 (15.7%) were prophylactic, and 158 of 189 (83.6%) were therapeutic. For 99 of 189 transfusion episodes, paired pre- and postplatelet counts were available within 24 hours. The median platelet count change was 5.0 × 10⁹ /L (5000/μL; range: -115 × 10⁹ /L to 158 × 10⁹ /L [-115,000 to 158,000/μL]); the posttransfusion platelet count was significantly higher than pretransfusion (P < 0.0001). The increase in platelet count after transfusion was greater in the prophylactic group than the therapeutic group (P = 0.0167). Transfusion reactions were suspected during 2 of 168 episodes (1.2%).

CONCLUSIONS

Immune-mediated thrombocytopenia was the most common disease process that resulted in PC transfusion. PC was more frequently administered to animals with active hemorrhage rather than prophylactically, and most dogs had evidence of hemorrhage in multiple organ systems, particularly the GI tract and skin. PC transfusions typically appeared safe, and the median platelet count increased after transfusion.

Isotretinoin treatment of 12 dogs with epitheliotropic lymphoma

BACKGROUND

Epitheliotropic lymphoma is an uncommon cutaneous malignancy of T lymphocytes. Limited information is available regarding the treatment and outcome of dogs with this disease.

OBJECTIVES

To evaluate the treatment outcome and toxicity profile of isotretinoin in dogs with epitheliotropic lymphoma.

ANIMALS

Twelve dogs with a diagnosis of epitheliotropic lymphoma were included.

MATERIALS AND METHODS

A medical database was searched for dogs diagnosed with epitheliotropic lymphoma and treated with isotretinoin between 2010 and 2021. Diagnosis, treatment details and tumour response were recorded for 12 dogs.

RESULTS

All lesions resolved in four of 12 (33%) treated dogs. Lesions visibly improved in a further three dogs, giving a response rate of 58%. Two dogs' lesions remained unchanged and three progressed despite therapy. Adverse effects occurred in three dogs (25%), all of which were rapidly resolving or not affecting quality of life.

CONCLUSION

Isotretinoin treatment was a well-tolerated and effective treatment for canine epitheliotropic lymphoma.

Procarbazine, prednisolone and cyclophosphamide (PPC) oral combination chemotherapy protocol for canine lymphoma

Orally administered daily chemotherapy offers a novel treatment approach for canine lymphoma in a population of dogs that have failed or not tolerated maximum tolerable dose chemotherapy. A multidrug oral chemotherapy protocol was designed and implemented for the treatment of fifty dogs with multicentric lymphoma with minimal side effects. The protocol consisted of oral procarbazine, prednisolone and cyclophosphamide (PPC) administered daily. Efficacy and toxicity were evaluated by clinical and laboratory evaluation. An overall response rate of 70% was achieved, with 24% and 46% of dogs having a partial and complete response, respectively, to treatment with the PPC protocol. Response to the PPC protocol (complete or partial) and age were the only factors identified as prognostic for time from initiation of the PPC chemotherapy until death. Overall, the protocol was very well tolerated with only one dog requiring protocol discontinuation due to grade 4 thrombocytopenia. Eight dogs recorded gastrointestinal toxicities, seven grade I and one grade II toxicity. These findings demonstrate that the administration of a continuous oral combination chemotherapy can provide comparable survival times in the rescue setting in dogs with multicentric lymphoma with minimal side effects.

Evaluation of the Tolerability of Combination Chemotherapy with Mitoxantrone and Dacarbazine in Dogs with Lymphoma

Combination chemotherapy can be an effective option for treating resistant lymphoma in dogs. This retrospective study examined the tolerability and efficacy of the combination of 5-(3,3-dimethyl-1-triazeno)-imidazole-4-carboxamide (dacarbazine) (DTIC) in a population of dogs with lymphoma resistant to a doxorubicin-containing chemotherapy protocol. Mitoxantrone was administered at 5 mg/m² IV over 10 min followed by DTIC at 600 mg/m² IV over 5 hr, every 3 wk. All dogs were treated with prophylactic trimethoprim-sulfadiazine and metoclopramide. The frequency of grade 4 neutropenia was 18%, and 5% of dogs were hospitalized from sepsis. Gastrointestinal toxicity was uncommon. The overall response rate was 34% (15 of 44; 95% confidence interval 20-48%) for a median duration of 97 days (range 24-636 days, 95% confidence interval 44-150 days). Fourteen of 15 dogs who received mitoxantrone and DTIC as first rescue responded to treatment. Dogs who achieved complete remission to their initial L-asparaginase, cyclophosphamide, doxorubicin, vincristine, and prednisone chemotherapy protocol were more likely to respond to mitoxantrone and DTIC (23 versus 11%, P = .035). The combination of mitoxantrone and DTIC is a safe treatment option for resistant lymphoma in dogs.

Phase I/II evaluation of RV1001, a novel PI3Kδ inhibitor, in spontaneous canine lymphoma

Background

RV1001 is a novel, potent, and selective PI3Kδ inhibitor. The purpose of this study was to evaluate the safety and efficacy of RV1001 in canine Non-Hodgkin lymphoma (NHL).

Methods and results

Inhibition of endogenous pAKT by RV1001 in primary canine NHL cells was determined by Western blotting. A phase I study of RV1001 was performed in 21 dogs with naïve and drug resistant T and B-cell NHL to assess safety, pharmacokinetic profile, and response to therapy. The objective response rate was 62% (complete response (CR) n = 3; partial response (PR) n = 10), and responses were observed in both naïve and chemotherapy-resistant B and T cell NHL. This study provided the recommended starting dose for a phase II, non-pivotal, exploratory, open label multi-centered clinical trial in 35 dogs with naïve and drug resistant T and B-cell NHL, to further define the efficacy and safety profile of RV1001. The objective response rate in the phase II study was 77% (CR n = 1; PR n = 26). Clinical toxicities were primarily hepatobiliary and gastrointestinal, and were responsive to dose modifications and/or temporary drug discontinuation. Hepatotoxicity was the primary dose limiting toxicity.

Conclusions

RV1001 exhibits good oral bioavailability, an acceptable safety profile, and biologic activity with associated inhibition of pAKT in dogs with B and T cell NHL. Data from these studies can be leveraged to help inform the design of future studies involving isoform-selective PI3K inhibitors in humans.

Metabolic Abnormalities Detected in Phase II Evaluation of Doxycycline in Dogs with Multicentric B-Cell Lymphoma

Doxycycline has antiproliferative effects in human lymphoma cells and in murine xenografts. We hypothesized that doxycycline would decrease canine lymphoma cell viability and prospectively evaluated its clinical tolerability in client-owned dogs with spontaneous, nodal, multicentric, substage a, B-cell lymphoma, not previously treated with chemotherapy. Treatment duration ranged from 1 to 8 weeks (median and mean, 3 weeks). Dogs were treated with either 10 (n = 6) or 7.5 (n = 7) mg/kg by mouth twice daily. One dog had a stable disease for 6 weeks. No complete or partial tumor responses were observed. Five dogs developed grade 3 and/or 4 metabolic abnormalities suggestive of hepatopathy with elevations in bilirubin, ALT, ALP, and/or AST. To evaluate the absorption of oral doxycycline in our study population, serum concentrations in 10 treated dogs were determined using liquid chromatography tandem mass spectrometry. Serum levels were variable and ranged from 3.6 to 16.6 µg/ml (median, 7.6 µg/ml; mean, 8.8 µg/ml). To evaluate the effect of doxycycline on canine lymphoma cell viability in vitro, trypan blue exclusion assay was performed on canine B-cell lymphoma cell lines (17-71 and CLBL) and primary B-cell lymphoma cells from the nodal tissue of four dogs. A doxycycline concentration of 6 µg/ml decreased canine lymphoma cell viability by 80%, compared to matched, untreated, control cells (mixed model analysis, p < 0.0001; Wilcoxon signed rank test, p = 0.0313). Although the short-term administration of oral doxycycline is not associated with the remission of canine lymphoma, combination therapy may be worthwhile if future research determines that doxycycline can alter cell survival pathways in canine lymphoma cells. Due to the potential for metabolic abnormalities, close monitoring is recommended with the use of this drug in tumor-bearing dogs. Additional research is needed to assess the tolerability of chronic doxycycline therapy.

Evaluation of a multi-agent chemotherapy protocol combining lomustine, procarbazine and prednisolone (LPP) for the treatment of relapsed canine non-Hodgkin high-grade lymphomas

The standard of care treatment for canine lymphoma is multi-agent chemotherapy containing prednisolone, cyclophosphamide, vincristine and an anthracycline such as doxorubicin (CHOP) or epirubicin (CEOP). Lomustine, vincristine, procarbazine, and prednisone (LOPP) has been evaluated as a rescue, with encouraging results; however, resistance to vincristine is likely in patients relapsing on CHOP/CEOP, and this agent may enhance LOPP toxicity without improving efficacy. The aim of this study was to evaluate responses to a modified-LOPP protocol that does not include vincristine (LPP) and is administered on a 21-day cycle. Medical records of dogs with high-grade multicentric lymphoma from 2012 to 2017 were reviewed. Dogs with relapsed lymphoma that received LPP as a rescue protocol were enrolled. Response, time from initiation to discontinuation (TTD) and toxicity of LPP were assessed. Forty-one dogs were included. Twenty-five dogs (61%) responded to LPP including 12 complete responses (CR) and 13 partial responses (PR). Responders had a significantly longer TTD (P < .001) compared to non-responders with 84 days for CR and 58 days for PR. Neutropenia was documented in 20 dogs (57%): 12 grade I to II, 8 grade III to IV. Thrombocytopenia was infrequent (20%): 5 grade I to II, 2 grade III to IV. Twelve dogs developed gastrointestinal toxicity (30%): 10 grade I to II and 2 grade III. Nineteen dogs had elevated ALT (59%): 9 grade I to II, 10 grade III to IV. Treatment was discontinued due to toxicity in 8 dogs (19%). The LPP protocol shows acceptable efficacy and toxicity-profile and minimizes in-hospital procedures.

Oral melphalan for the treatment of relapsed canine lymphoma

Oral melphalan has been included in multi-agent rescue protocols for canine lymphoma but its activity as a single-agent for this purpose has not been established. Inexpensive cost, ease of administration and tolerability make oral melphalan an attractive candidate for single-agent rescue therapy of canine lymphoma. Retrospective evaluation of 19 cases of relapsed canine lymphoma treated with oral melphalan was performed. Melphalan was primarily administered (n = 16) via a high dose protocol (HDM) with a median dosage of 19.4 mg m^-2 . Fifteen dogs (78.9%) were treated concurrently with corticosteroids. Response evaluation was possible for all dogs with a calculated overall clinical benefit (partial response [PR] + stable disease [SD]) of 31.6% (PR 3/19; SD 3/19). Times to progression following melphalan (TTP-M) were 14, 24 and 34 days for responders and 20, 28 and 103 days for dogs experiencing SD. Twelve of 17 dogs evaluable for toxicity experienced an adverse event (AE) with only 3 dogs experiencing a grade III or higher AE. Haematologic toxicity was common (11/17) while gastrointestinal toxicity was rare (1/17). Although treatment resulted in limited clinical benefit and non-durable responses, oral melphalan was well-tolerated and may be a reasonable rescue option in cases where minimal effective agents remain.

Efficacy of dacarbazine as a rescue agent for histiocytic sarcoma in dogs

BACKGROUND

Canine histiocytic sarcoma (HS) is an aggressive neoplasm that is generally associated with a poor prognosis. CCNU is considered first-line medical therapy, although the majority of dogs ultimately develop progressive disease. The objective of this study was to evaluate the efficacy of dacarbazine as a rescue agent for HS.

MATERIALS AND METHODS

Medical records of dogs diagnosed with HS that received at least one dose of dacarbazine were reviewed. Information collected and analyzed included signalment, disease distribution, treatment history, dacarbazine treatments (including dose, interval and total number of cycles), adverse events, and response to treatment.

RESULTS

Seventeen dogs were included, all of which had disseminated or metastatic disease and had received prior treatment with CCNU. Three dogs achieved partial remission for an overall response rate of 17.6%. The overall median event-free survival (EFS) was 21 days. For dogs that experienced an objective response, the EFS was 70 days. Toxicity secondary to dacarbazine was generally mild and self-limiting.

CONCLUSION

In the setting of advanced disease, dacarbazine appears to have modest activity against HS and warrants further investigation.

Clinical Response and Adverse Event Profile of Bleomycin Chemotherapy for Canine Multicentric Lymphoma

Although canine multicentric lymphoma is initially responsive to multidrug chemotherapy, resistance and relapse create a need for novel chemotherapeutics. Bleomycin is an antitumor antibiotic with a minimal adverse event profile; though commonly used for human non-Hodgkin's lymphoma, its use is poorly characterized in dogs. The purpose of this retrospective case series was to describe the clinical response and adverse event profile of systemic bleomycin for canine multicentric lymphoma (n = 10). A partial response was noted in one dog that died 24 days later due to unrelated disease. Adverse events were infrequent and limited to grade 1 gastrointestinal and grade 1 constitutional toxicity. Although clinical response was minimal, systemic bleomycin was well tolerated when administered at 0.5 U/kg. Additional studies are warranted to determine the influence of administration schedule and dose on the efficacy of bleomycin for veterinary neoplasia.

Safety, tolerability and pharmacokinetic properties of the novel triazene TriN 2755 in tumour bearing dogs - a phase I study†

TriN 2755 is an alkylating antineoplastic agent for intravenous (IV) use, carrying the triazene group as the cytotoxic principal. Using a standard 3 + 3 design, a phase I study was performed in tumour bearing dogs to determine the maximum tolerated dose (MTD), the dose limiting toxicity (DLT), and pharmacokinetic (PK) profile of TriN 2755. Thirty dogs were included in the study. TriN 2755 was administered over 20 min on two consecutive weeks per month for a total of three cycles. The starting dose was 25 mg kg^-1 and the MTD was 74.6 mg kg^-1 . Three dogs experienced DLT, which was characterized by gastrointestinal adverse events. The PKs of TriN 2755 and its main metabolites in plasma and sputum are described in a two-compartment model. The response rate for 19 of 30 dogs was 47.3% (six partial remission, three stable disease) and the median progression-free interval (PFI) for the responders was 47 days (range: 21-450 days).

Comparison of doxorubicin-cyclophosphamide with doxorubicin-dacarbazine for the adjuvant treatment of canine hemangiosarcoma

Canine hemangiosarcoma (HSA) is a neoplasm of vascular endothelial origin that has an aggressive biological behaviour, with less than 10% of dogs alive at 12-months postdiagnosis. Treatment of choice consists of surgery followed by adjuvant doxorubicin-based chemotherapy. We prospectively compared adjuvant doxorubicin and dacarbazine (ADTIC) to a traditional doxorubicin and cyclophosphamide (AC) treatment, aiming at determining safety and assessing whether this regimen prolongs survival and time to metastasis (TTM). Twenty-seven dogs were enrolled; following staging work-up, 18 were treated with AC and 9 with ADTIC. Median TTM and survival time were longer for dogs treated with ADTIC compared with those receiving AC (>550 versus 112 days, P = 0.021 and >550 versus 142 days, P = 0.011, respectively). Both protocols were well tolerated, without need for dose reduction or increased interval between treatments. A protocol consisting of combined doxorubicin and dacarbazine is safe in dogs with HSA and prolongs TTM and survival time.

Treatment-related toxicities in tumor-bearing cats treated with temozolomide alone or in combination with doxorubicin: a pilot assessment

A retrospective study assessing treatment-related toxicities in tumor-bearing cats treated with temozolomide (TMZ) alone or in combination with doxorubicin was conducted. TMZ was administered orally once a day for 5 days every 3 weeks at a dose of 20 mg/cat. Tumor response was evaluated with standard World Health Organization criteria and toxicity was monitored using veterinary co-operative oncology group-common terminology criteria for adverse events (VCOG--CTCAE) criteria. Ten tumor-bearing cats with various types of malignancies were treated with TMZ-based chemotherapy. Eight cats were evaluable for response. Two cats achieved a complete response, one achieved stable disease and five achieved a partial response. Four grade III and one grade IV hematological toxicities, and one grade IV gastrointestinal toxicity were observed. Four cats were euthanased as a result of apparent toxicity. One cat was euthanased as a result of severe and prolonged myelosuppression with fever. Three were euthanased for grade III pleural and pericardial effusions. Effusion was seen in cats treated with higher cumulative dose of TMZ (P = 0.0046). Planned additional case accrual was discontinued because of unacceptable levels of toxicity despite evidence of efficacy in some of the cats. Additional investigation is needed to elucidate this unexpected apparent cumulative toxicity.

Evaluation of the University of Florida lomustine, vincristine, procarbazine, and prednisone chemotherapy protocol for the treatment of relapsed lymphoma in dogs: 33 cases (2003-2009)

OBJECTIVE

To evaluate the toxicity and efficacy of a modification of a previously evaluated combination of lomustine, vincristine, procarbazine, and prednisone (LOPP) as a rescue protocol for refractory lymphoma in dogs.

DESIGN

Retrospective case series. Animals-33 dogs with a cytologic or histologic diagnosis of lymphoma that developed resistance to their induction chemotherapy protocol.

PROCEDURES

Lomustine was administered on day 0 of the protocol. Vincristine was administered on day 0 and again 1 time on day 14. Procarbazine and prednisone were administered on days 0 through 13 of the protocol. This cycle was repeated every 28 days.

RESULTS

Median time from initiation to discontinuation of the University of Florida LOPP protocol was 84 days (range, 10 to 308 days). Overall median survival time was 290 days (range, 51 to 762 days). Overall response rate with this protocol was 61% (20/33), with 36% (12) having a complete response and 24% (8) having a partial response. Toxicosis rates were lower than for the previously published LOPP protocol.

CONCLUSIONS AND CLINICAL RELEVANCE

The University of Florida LOPP protocol may be an acceptable alternative to the mechlorethamine, vincristine, procarbazine, and prednisone protocol as a rescue protocol for dogs with lymphoma.

The staging and treatment of multicentric high-grade lymphoma in dogs: a review of recent developments and future prospects

In recent years, considerable progress has been made in understanding the biology of canine lymphoma with resultant enhanced classification schemes and the possibility of individualised, tailored therapies. However, although complete remission may be achieved using multi-agent chemotherapy, the mortality rate from this neoplasm remains high. This review focuses on the staging of high-grade multicentric lymphoma in the dog, on conventional and novel treatment strategies (including chemotherapy, bone marrow transplantation, radiation therapy and molecular-targeted agents), and on the management of relapsed or refractory cases.

Evaluation of the prognostic significance of BCL6 gene expression in canine high-grade B-cell lymphoma

The clinical usefulness of BCL6 gene expression was evaluated as a prognostic indicator in dogs with high-grade B-cell lymphoma. Forty-four dogs were diagnosed with centroblastic or B-cell immunoblastic type lymphoma according to the updated Kiel classification. BCL6 mRNA expression was measured by real-time PCR and its relationship with prognosis was analyzed. Progression-free and overall survival was not significantly different between the high BCL6 expression group (higher than the median) and the low BCL6 expression group (lower than the median) (P=0.99 and P=0.61, respectively). No correlation between BCL6 and prognosis was observed in this study, which is inconsistent with findings reported for human diffuse large B-cell lymphoma. BCL6 protein expression was not detected in the 11 dogs evaluated by immunohistochemistry. Furthermore, BCL6 protein expression was assessed in 13 archived paraffin-embedded high-grade canine lymphoma tissues and all were also negative. The results suggest that most canine high-grade B-cell lymphomas correspond to human diffuse large B-cell lymphoma with no immunohistochemical expression of BCL6.