Practical Oncology Mast Cell Tumor Wendy Blount, DVM

Mast Cell Tumor Mast cell granules contain histamine and heparin, among other things Degranulation is largely responsible for symptoms Release of histamine Increased gastrin secretion (anorexia, ulcers, hematemesis) Anaphylactoid reaction Release of heparin – less clinically significant

Mast Cell Tumor Most often found on the skin Most common skin tumor in the dog Brachycephalics & retrievers predisposed 2nd most common cancer in dogs Also visceral & elsewhere Gastrointestinal, Spleen, bone marrow Less common sites Oropharyngeal Mediastinum CNS Nail bed, ocular & periocular

Mast Cell Tumor Can have many different appearances Can be infiltrated with fat Symptoms can be waxing and waning Tumor gets bigger and smaller over time 5-15% have multiple masses at presentation 20-50% will have more MCT in the future, even if the first are cured

Staging for Metastasis x x

Etiology Allergic skin disease? C-KIT mutation (aka SCFR, CD117) In “high risk MCT” (high grade II & all grade III) These have decreased survival time can be treated with tyrosine kinase inhibitors (Palladia & Kinavet-CA1 ) SCFR – stem cell factor receptor C-KIT normally regulates proliferation, migration and differentiation When C-KIT is mutated, it is constantly turned on, dysregulating cell growth an promoting malignancy

Clinical Signs GI Signs Pruritus and skin flushing Facial swelling Anorexia, vomiting, melena Pruritus and skin flushing Facial swelling Weakness, lethargy Delayed wound healing Darier’s Sign swollen, itchy, red skin after scratching or stroking the skin

Clinical Signs GI Signs Pruritus and skin flushing Facial swelling Anorexia, vomiting, melena Pruritus and skin flushing Facial swelling Weakness, lethargy Delayed wound healing Darier’s Sign swollen, itchy, red skin after scratching or stroking the skin

Diagnosis FNA Cytology often diagnostic Round cells with or without granules Granules intracellular or in background Granules form a halo around the relatively pale nucleus eosinophils Give diphenhydramine before or right after aspiration FNA can cause degranulation Dexamethasone as well if mass is visibly inflamed

Mast cell granules - fine Diagnosis Mast cell granules - fine

Diagnosis LSA azurophilic granules – coarse Lymphoid cells have less cytoplasm than mast cells

Diagnosis Poorly granulated MCT

Agranular mast cell tumor Resembles histiocytoma Diagnosis Agranular mast cell tumor Resembles histiocytoma

Diagnosis

Staging for Metastasis Histopathology for grading Excisional if resectable Incisional if not May not heal well Degranulation may be a problem FNA draining lymph node Clusters of mast cells likely metastasis Single mast cells likely not Abdominal US with FNA liver and spleen CBC, panel, buffy coat

Staging for Metastasis Staging less important for high risk MCT High grade II & Grade III palliative treatment for best outcome Palliative drugs, chemo, radiation Cure is unlikely, especially for grade III (Maddie) Staging more important for single local low grade II that is not resectable If staging is clean for metastasis, then radiation can be curative (Sadie)

Staging for Metastasis Non-resectable MCT

Staging for Metastasis Non-resectable MCT

Staging for Metastasis Non-resectable MCT

Staging for Metastasis Lymph node cytologies

Staging for Metastasis Lymph node cytologies

Staging for Metastasis Lymph node cytologies

Tumor Stage (WHO) Stage 0 – microscopic disease only Stage I – tumor confined to the dermis Stage II – tumor does not infiltrate subcutaneous tissues, lymph node metastasis Stage III – large, infiltrating tumor (or multiple tumors) Stage IV – distant metastasis Consideration is being given to reducing stage of multiple dermal tumors

Histopathology grade Mitotic Index (MI) Surgical margins – clean, narrow or dirty Invasiveness – dermal or invasive (subcutaneous/muscle) Histopathology tells a great deal about prognosis and treatment indicated for mast cell tumors Staging tells less, unless single unresectable low grade II

x

Histopathologic Grading Grade I – well differentiated, behaves benignly (dermal in cats) Grade II – intermediate differentiation, behavior is widely variable Low grade II – often behaves benignly High grade II – may have C-kit mutation, often behaves malignantly Grade III – anaplastic, aggressive behavior This is the Patnaik System

Histopathologic Grading We used to think grade II unpredictable Now that we divide grade II into low and high, there is much more predictability Most path labs now give you high or low grade II in the report Be sure to request this and for border reads More information from MSU prognostic panel (form) - $210 Obsolete system has grade I the worst and grade III the best prognosis

Surgery Mainstay of low grade MCT treatment Mast Cell Tumors often extend well beyond the visible mass Diagnose by FNA before you excise Lateral margins 2-3 cm beyond visible mass Small tumors <1 cm, 1.5-2cm margins may be adequate One fascia layer deep to visible mass Avoid manipulating the tumor Intraoperative cytologies on 4 lateral and deep margins can be helpful

Surgery Prednisone for pre-surgical cytoreduction Out of favor by oncologists at this time I still like use it Stabilizes lysosomal membranes – may prevent degranulation caused by surgery Controls inflammation around the tumor so tumor borders are easier to see Usually makes the dog feel better, so client perceives better toleration of surgery Prednisone 40 mg/m2 PO SID x 7days, then 20 mg/m2 PO SID x 7days, then QOD

Surgery Re-excision where borders are dirty on grade I or II Grade III tumors considered systemic More surgery only for local palliation 3 cm beyond original surgery One fascia layer deeper than original surgery Complete resection results in long survival If clean borders, 95% cured with second excision, using these rules

Surgery NeoAdjuvant Therapy Given to a patient with non-resectable tumor in hopes of making it resectable Chemotherapy and/or radiation Best managed by medical and/or radiation oncologists Need to understand effects of neoadjuvant therapy on healing and when and how to do surgery

Chemotherapy Not indicated for multiple dermal MCT that are cured by excision To deal with multiple dermal MCT when removing all becomes impossible To deal with MCT at the tumor borders when radiation not possible Radiation more likely to be curative To improve post-surgical prognosis for high risk grade II and all grade III MCT To palliate metastatic or systemic disease Surprisingly, there are few studies to evaluate efficacy of various protocols

Chemotherapy Two categories: Traditional chemo VP – vinblastine prednisone CCNU – popular 20 years ago Alternating VP and CCNU CVP – cyclophosphamide vinblastine pred TKI – tyrosine kinase inhibitors Palladia Kinavet

Chemotherapy Vinblastine and prednisone (VP) Median survival 134 days (5 months) – gross disease after surgery Median survival 1013 days (3 years) – microscopic disease after surgery 45% survival at 2 years Half of these had surgery prior to chemo Most grade III have gross disease after surgery Most dead in 2-6 months All gone within the year Vinblastine 2-2.2 mg/m2 IV slow IV push once weekly for 4 weeks, then every other week for 4 doses Prednisone 40 mg/m2 PO SID, then 20 mg/m2 PO SID x 2 weeks, then 20 mg/m2 PO QOD (intervals)

Chemotherapy CCNU 60-70 mg/m2 PO q3-4 weeks 4 week interval the first time, then shorten if symptoms return during the 4th week Baseline liver tests (ALT, SAP, albumin, bile acids) Pretreat with diphenhydramine Check before 3rd dose and then prior to each Stop if signs of liver disease to prevent liver failure 6-8 doses common maximum I have reached 12 at most Grade III median survival 2 months

Chemotherapy Alternating VP and CCNU Alternate vinblastine and CCNU every 2 weeks for a total of 8 treatments Doses on previous slides Prednisone 2 mg/kg PO SID tapered gradually to maintenance dose of 0.5 mg/kg PO SID x 6 months Macroscopic disease grades II and III 3 remission, 4 PR median duration of response 58 days 2 patients did not reach 4th CCNU treatment due to ALT >1000

Chemotherapy Vinblastine, prednisone, cyclophosphamide All dogs had either high grade II with lymph node metastasis or grade III MCT Dogs with macroscopic disease: 4 grade II, 7 grade III 64% had a measurable response to treatment 46% CR, 18% PR 18% SD, 18% PD Median PFST was 74 days Median OST was 145 days 54% also had radiation treatment

Chemotherapy Vinblastine, prednisone, cyclophosphamide Dogs with microscopic disease: 22 grade II, 3 grade III 10 recurrent disease, 2 multiple tumors, 13 first time single tumor Two subgroups: A – 19 dogs with local microscopic disease. Median PFST was 222 days (7 months) Median OST was >2092 days (6 years) B - 5 dogs with absolute local control (ALC) Median PFST was 865 days (2.5 yrs) median OST was >1261 days (3.5 years)

Chemotherapy Vinblastine, prednisone, cyclophosphamide Protocol: Prednisone 1 mg/kg PO SID, tapered and discontinued over 24 – 32 weeks Week 1 - Vinblastine 2-2.2 mg/m2 IV Week 2 - Cyclophosphamide 200–250 mg/m2 either PO over 4 days or IV on day 1 Week 3 – prednisone only Continue 3 week cycle for 6 months, or until death or chemo abandoned

Chemotherapy Vincristine alone not effective for MCT Historically, many dirty border grade II did very well with most chemo protocols many months, years or cured Historically, some grade II with dirty borders spontaneously resolved Are malignant MCT indistinguishable from inflammatory reaction? Now that we can divide grade II into low and high grade, prediction of behavior is more accurate Even so, even high grade II with dirty borders or metastasis can do very well with chemo and/or radiation Grade III is still way worse than high grade II

Chemotherapy - Summary Traditional chemo VP or alternating VP & CCNU preferred to CCNU alone for grade III TKI Studies comparing traditional to TKI not available many oncologists prefer TKI as first line therapy for high risk MCT Others do traditional chemo, then follow with TKI Many oncologists feel that if there is a good response to TKI, it is more durable than traditional chemo Side effects of TKI are not common in the first 6 weeks, but eventually occur, can be significant and potentially life threatening

Chemotherapy

Chemotherapy Palladia and Kinavet-CA1/Masivet Tyrosine kinase (TKI) inhibitors Prednisone and TKI are the chemo drugs with direct cytotoxicity for MCT Probably the most effective chemo for high grade MCT Not appropriate for low grade MCT due to toxicity A game changer for high grade very large MCT

Chemotherapy Palladia and Kinavet-CA1/Masivet 25% of grade II & III MCT have C-KIT mutation Blocking wild type or mutated KIT causes apoptosis in MCT antiproliferative through KIT blockade antiangiogenic through other MOA

Chemotherapy Palladia and Kinavet-CA1/Masivet Indications for use: Dogs >11-15 lbs only (not cats) Non-resectable MCT Dirty borders after re-excision Multiple diffuse or coalescing high grade MCT Concurrent conditions precluding surgery or multiple sedations for radiation therapy High grade MCT or C-KIT mutation Indicated with or without metastasis Post Chemo – VP x 4 weeks, then Palladia

Chemotherapy x

Chemotherapy Palladia and Kinavet-CA1/Masivet Though both are TKIs, there can be resistance to one but not the other If one fails, try the other Stable disease is a victory with either Palladia has more broad spectrum activity, and is thought to be more likely to cause clinical response than Kinavet Kinavet response can take up to 2-3 weeks Gleevec is a TKI used in people, but it is very expensive ($100-150 per pill) Palladia $6-800, Kinavet $500 /month - 70lb dog

Chemotherapy Kinavet Administration 12.5 mg/kg PO SID Dose chart on package insert (Client Info) Cannot be used in dogs weighing less than 15 pounds Dose reduction in response to adverse events stop Kinavet for 1-2 weeks Reduce dose to 9 mg/kg/day when resumed Weekly CBC/panel for the first 6 weeks Then every 3 weeks x 2 Then every 6 weeks thereafter

Chemotherapy Palladia Administration 2.5 mg/kg PO QOD (or MWF) Dose chart on package insert is higher With or without food Dose reduction in response to adverse events Stop Palladia for 1-2 weeks 0.5 mg/kg reduction when reduced Minimum dose 2.2 mg/kg PO QOD Weekly CBC/panel for the first 6 weeks Then every 3 weeks x 2 Then every 6 weeks thereafter

Chemotherapy Palladia Administration GI side effects common Make sure owner knows to STOP drug if anorexia, vomiting, diarrhea Dispense Cerenia and metronidazole at the first visit to have on hand Administer H1 and H2 blockers concurrently

Chemotherapy Palladia Study – Bergman & Clifford, 2009 Dogs with progressive disease on the blinded phase could enter open-label phase at any time

Chemotherapy Palladia Study – Bergman & Clifford, 2009 Statistically significant improvement in objective response rate

Chemotherapy Palladia Study – Bergman & Clifford, 2009 57.2% did not respond Among responders, median duration of response was 12 weeks (3 months) Median time to non-response or death was 18 weeks (4-5 months) 82% of dogs with C-KIT mutation responded 54% of dogs without mutation responded There was a placebo response Likely due to spontaneously resolving degranulation Clin Cancer Res 2009; 15:3856-3865.

Chemotherapy Palladia Side effects

Chemotherapy Palladia Side effects Dec. albumin – 13% Palladia, 8% Placebo Palladia given long term leads to glomerular disease and renal failure While this side effect is severe, it is balanced against the grave prognosis of high grade MCT

Chemotherapy Kinavet-CA1

Chemotherapy Kinavet-CA1

Chemotherapy Palliative Drug Therapy Alone, or accompanying chemo and/or radiation Prednisone 40 mg/m2/day Wean gradually to 0.5 mg/m2/day Antihistamines daily H2 blocker or proton pump blocker Cimetidine, ranitidine, famotidine Omeprazole, esomeprazole sucralfate if ulcerated Hematemesis, melena

Radiation Therapy Curative Palliative Low grade II non-resectable MCT without distant metastasis Grade II Stage 0 MCT with dirty margins Disease free interval is increased compared to no treatment Similar outcome to re-excision (95% cure) Palliative Non-resectable high grade MCT Regional lymph node metastasis No indication to irradiate grade II MCT with clean borders

Treatments Not Recommended Deionized water injections At one time recommended for cytoreduction prior to surgery Subsequent studies have proven ineffective Risk causing degranulation Pain on injection intralesional Vetalog or DepoMedrol Historically for those dogs who have too many dermal MCT to remove and no evidence of systemic disease replaced by TKI or palliative drugs

Prognosis Stage and grade much more important for MCT and than for LSA Grade I with clean borders are cured by surgery Low grade II clean borders usually cured by surgery and/or radiation High grade II clean borders should probably have adjunctive chemo and/or radiation High grade II with dirty borders should definitely have adjunctive chemo and/or radiation and may have poor prognosis Virtually all of grade III die of their disease, often within a few months, unless very small with clean borders

Prognosis Indicators of poor prognosis Dirty borders after re-excision High grade, advanced stage, MI >5 Breed- Shar pei Systemic signs due to degranulation Size and growth rate Location – perineum, scrotum, nail bed, mucocutaneous, muzzle C-kit mutation and other histopath prognostic indicators (MSU/AMC panels)

Prognosis Indicators of better prognosis Clean borders on excision Low grade, low stage, MI <5 Breed – Boxers and Pugs

Prognosis Indicators of better prognosis Clean borders on excision Low grade, low stage, MI <5 Breed – Boxers and Pugs

Prognosis Indicators of better prognosis Clean borders on excision Low grade, low stage, MI <5 Breed – Boxers and Pugs Multiple primary mast cell tumors do not necessarily worsen prognosis Dogs who tend to get one dermal MCT tend to get more, simultaneously or sequentially Warn owners to look for more when you remove the first

Prognosis x

Prognosis MCT prognostic panel Not indicated for grade I or III gives more information for grade II Do chemo/radiation if high grade II Amputate or radiate non-resectable low grade II Cost is about $210 plus shipping Send MCT histopath to MSU or AMC, so you can add the prognostic panel if grade II Save center of tumor in formalin to send to MSU /AMC for panel later if grade II Can be difficult to get unstained paraffin sections from the first lab (except TVMDL)

Client Handouts Mast Cell Tumors Kinavet Palladia Chemo agents discussed Sunday

Acknowledgements Philip J. Bergman, DVM, MS, PhD, DACVIM (Oncology) VIN Consultant, CMO BrightHeart Vet Centers Louis-Philippe de Lorimier, DVM, ACVIM (Oncology) VIN Consultant, U of Ill Urbana-Champaign Visiting assistant professor, medical oncology Karri A. Meleo, DVM, ACVIM (Oncology), ACVR VIN Consultant, Vet Onc Serv, Edmonds, WA

Acknowledgements Robert C. Rosenthal, DVM, BS, MS, PhD VIN Consultant Kurt R. Verkest, BVSc, BVBiol, MACVSc (Small Animal) VIN Associate Editor, Univ Queensland, Australia Claudia Barton, DVM, ACVIM (Internal Medicine, Oncology) TAMU CVM

Acknowledgements Craig Clifford, DVM, MS, ACVIM (Oncology) VIN Consultant Zachary Wright, DVM, ACVIM (Oncology) Animal Diagnostic Clinic, Dallas TX