Oncology Flashcards
What is cancer?
Persistent, purposeless proliferation of host cells, often to the detriment of the host
What are overactive oncogens?
Tumour promoting genes that are secondary to mutation
What is the most common gene alteration in human cancer?
Loss of P53
Is a tumour suppressor gene that stops mitosis if there is any DNA damage
What does neoplasia mean?
New/abnormal growth
What are the two features that tumours are described according to?
Tissue of origin
Status
What are benign squamous epithelial tissue tumours called?
Papilloma
What are benign glandular epithelial tissue tumours called?
Adenoma
What are malignant squamous epithelial tissue tumours called?
Squamous cell carcinoma
What are malignant glandular epithelial tissue tumours called?
Adenocarcinoma
What are benign bone mesenchymal tissue tumours called?
Osteoma
What are benign blood vessel mesenchymal tissue tumours called?
Haemangioma
What are malignant bone mesenchymal tissue tumours called?
Osteosarcoma
What are malignant blood vessel mesenchymal tissue tumours called?
Haemangiosarcoma
What are lymphocyte tumours called?
Lymphoma
What is the growth fraction?
The proportion of actively dividing cells in a tumour
When is a tumour most susceptible to treatment?
When the cells are rapidly dividing rather than when the growth fraction reaches a plateau
What type of tumour is an exception bcos it maintains a high growth fraction?
Lymphoreticular tumour - lymphoma
What stage of the cell cycle is resistant to drugs/radiation?
G0 - resting
Important as reservoir of cells can repopulate tumour
In what stage of the cell cycle is chemotherapy most effective?
M phase - mitotic
What stage of the cell cycle is most radioresistant?
S phase
What does the tumour grade depend on?
The mitotic rate
Cellular and nuclear characteristics
What are clues of local invasion of the tumour?
Indistinct boundaries
FIxed in more than one plane
Thickened adjacent tissue
Spontaneous bleeding
What are the 4 methods of metastatic spread?
Blood
Lymphatics
Transcoelomic - across pleural/peritoneal spaces
Iatrogenic - seeding
What are paraneoplastic syndromes?
Signs arising fron the indirect effect of tumours production and release of biologically active substances
What is a haematologic paraneoplastic syndrome?
Anaemia
What is myelophthisis?
When neoplastic invasion directly affects the bone marrow
What does myelophthisis cause?
Cytopenias - decreased production of WBC, RBC etc
What is leukaemia?
When abnormal cells are released into the blood from the bone marrow
How can tumours affect blood cell production?
Myelofibrosis - Replacement of bone marrow with scar tissue
What are 3 causes of blood loss form tumours?
Local haemorrhage
Gastric ulcer from mast cell tumour
Bleeding disorder - thrombocytopenia
What can mast cell tumours cause?
Hyperhistaminaemia
What local effects does hyperhistaminaemia cause?
Oedema
Localised bleeding
Delayed wound healing
What systemic effects does hyperhistaminaemia cause?
Anaphylactic shock
Gastroduodenal ulcer
What is an immune mediated reaction that cancer can cause?
Cross reactivity between cancer cells and healthy cells
What is the most common paraneoplastic syndrome in dogs?
Hypercalcaemia
What causes hypercalcaemia as a paraneoplastic syndrome?
Tumours release a substance called parathyroid hormone-related peptide
What are 3 clinical signs of hypercalcaemia?
PUPD
Muscle weakness
Dehydration/renal failure
What are the two kinds of biopsy?
Cytology
Histopathology
What can cytology determine?
The nature of the tumour eg. Epithelial, mesenchymal
What are some types of cytological methods?
Fine needle aspirates
Touch preparations
Cytospins
What are the features of malignancy?
degree of differentiation cell pleomorphism multiple nuclei anisocytosis nuclear : cytoplasmic ratio mitotic figures clumping of chromatin nuclear pleomorphism multiple nucleoli
What are some types of histological examination?
Surgical - incisional and excisional
Needle
Punch biopsy
What is an incisional surgical biopsy?
Where a piece of the tumour and some healthy tissue is removed
What is an excisional surgical biopsy?
Remove entire cancer plus healthy tissue around it
What are 3 rules of biopsy?
Avoid superficial ulceration/inflammation/necrosis
Ensure adequate depth
Try to include a boundary
What does clinical staging aim to identify?
Cytological grade
Local invasion
Metastatic spread
What is the most common staging system used for cancer?
TNM
T - primary Tumour
N - regional lymph Nodes
M - Metastasis
What determines T in the TNM staging system?
Size and extent of the primary Tumour - up to T4
What determines N in the TNM staging system?
The amount of involvement of the regional lymph Nodes - up to N4
What does M determine in the TNM staging system?
Whether Metastasis is present or not - up to M2
What is M1 and M2 in the TNM staging system?
M1 - single metastasis
M2 -multiple metastasis
What is remission?
When all clinical evidence of cancer has disappeared, but occult cancer cells remain and relapse will occur at some point
What is the only thing that has a chance of curing cancer?
Complete surgical excision
When is local excision used?
Only for truly benign tumours
eg. Fibroma, lipoma
What constitutes wide local excision?
Wider margins - 1 cm
In two tissue planes
When is wide local excision used?
Locally invasive tumours
eg. basal/squamous cell carcinoma
Mast cell tumour
What is compartmental excision?
Resection - removes every tissue compartment with the tumour involves
When is compartmental excision used?
Solid soft tissue sarcomas that infiltrate wider than 1-2cm
What is the most common type of radiation therapy?
External beam radiation therapy
What is brachytherapy?
Radioactive substance emits gamma rays or beta particles close to the tumour
Either on surface or implanted into tumour
What type of brachytherapy is used to treat thyroid tumour?
Radioiodine treatment
What is the most common source of external beam in external beam radiation therapy?
Linear accelerator
When should radiation therapy be used?
Malignant primary tumour with no local/distant metastasisq
What does the response to radiation of the cancer cells depend on?
Radiosensitivity of the cells - rapidly dividing cells are more sensitive
Dose and energy of radiation
What are some acute reactions to radiation therapy?
Skin reddening Vesiculation Desquamation Severe exfoliative dermatitis Localised hair loss
What are some late toxicity symptoms of radiation therapy?
Depigmentation Dermal fibrosis Osteonecrosis Neural necrosis Blindness (enucleation) Neurologic signs
When should chemotherapy be used?
In the early stages - depends on growth fraction as rapidly dividing cells are most susceptible
What does the response to chemo depend on?
Tumour growth rate
Drug resistance
What does fractional cell kill mean?
Cytotoxic drugs only kill a constant fraction of cancer cells - according to first order kinetics
What is the consequence of fractional cell kill?
Difficult to fully eradicate all cancer cells - if start with low number, an even lower number still remain
How do you get around the issue of fractional cell kill?
Use chemotherapy protocol - multiple doses
Surgical debulking
What is primary cytotoxic drug resistance?
Cancer is resistant in the first place
What is secondary cytotoxic drug resistance?
Cancer develops resistance due to mutations and selection of resistant clones
What is multidrug resistance I?
Mutation of the gene encoding the ATP binding cassette export pump
Leading to accumulation of the drug in the cells
Which chemo drugs are affected by multidrug resistance I?
Ivermectin
Doxorubicin
Vincristine
Vinblastine
What are some safety issues with chemo drugs?
Cause DNA damage so Carcinogen - cause cancer Teratogen - damage foetus Irritant Mutagenic
How does coat change during chemo?
Cats only lose whiskers
Some dog breeds susceptible to coat loss
Others just lose beard
What are two other side effects of chemo other than coat loss?
GI toxicity
Myelosuppression - neutropenia
What is myelosuppression?
Decreased bone marrow activity
When is myelosuppression an issue? What should you do?
When neutrophil count is <2x10^9 - at risk of sepsis
Stop chemo, give antibiotics
What can happen if given topically/extravascular?
Phlebitis - tissue necrosis
What does vesicant mean?
Severe irreversible tissue injury and necrosis
What are some drugs that are vesicants?
Vincristine
Cisplatin
Doxorubicin
How to reduce chance of extravasation/perivascular leakage?
Administer through IV catheter
Flush catheter with saline
What is sterile haemorrhagic cystitis?
Metabolites in urine are bladder irritant
What are acute and chronic cardiotoxicities due to chemo?
Acute - tachyarrhythmias
Chronic - cardiomyopathy
How often do you give chemo drugs?
3 week cycles
What are the 3 phases of chemotherapy protocol?
Induction
Maintenance
Rescue
What is the aim of induction in the chemotherapy protocol?
Aim to reduce tumour burden into remission
When is rescue phase of the chemotherapy protocol?
When the tumour relapses or doesnt respond to initial therapy
What tumours are highly sensitive to chemotherapy?
Lymphoma
Myeloma
What tumours are poorly sensitive to chemotherapy?
Slow growing sarcomas
Carcinomas
Melanomas
What are the two most common chemotherapy protocols used for lymphoma?
COP - cats
CHOP - B cell dogs
LOP - T cell dogs
What drugs are in the COP protocol?
Cyclophosphamide
Prednisolone
Vincristine
What drugs are in the CHOP protocol?
Cyclophosphamide
Prednisolone
Vincristine
Hydroxydaunorubicin - doxorubicin
What is first-line chemotherapy?
When chemo is used at first in systemic diseases that cant debulk
Might respond well as have high growth fraction
What is adjunctive chemotherapy?
Used alongside surgery/radiotherapy
When is adjunctive chemotherapy used?
For solid tumours eg. carcinoma, sarcoma
What is metronomic chemotherapy?
Palliative daily low doses of chemotherapy drugs
What is chemoembolisation?
When chemo drugs are injected into blood vessel supplying tumour
Then block tumour with synthetic material
What are the main mechanisms of chemotherapy drugs?
Alkylating agents
Platinum compounds
Plant alkaloids
Antibiotics
How do alkylating agents work to be cytotoxic?
They add an alkyl group to guanine which damages DNA
Cause inter/intra strand crosslinks
When do alkylating agents work in the cell cycle?
They are not cell cycle specific
What are some examples of alkylating agent chemo drugs?
Cyclophosphamide
Chlorambucil
Melphalan
How do platinum compounds woth to be cytotoxic?
They covalently bind to DNA causing DNA damage
Cause inter/intra strand crosslinks
(Similar to alkylating agents)
What are some examples of platinum compounds chemo drugs?
Cisplatin
Carboplatin
What type of tumour are platinum compounds used for?
Osteosarcoma
What is important to note about platinum compounds?
They are nephrotoxic to cats - dont use
How do anti-metabolites work?
Inhibit the use of cellular metabolites during the cell growth/division
What are 5 examples of anti- metabolites?
Cytarabine Methotrexate 5-fluorouracil Azathioprine Hydroxyurea
What is cytarabines mechanism of action?
Cytosine analogue
What phase does cytarabine damage DNA in?
S phase
What type of tumour is cytarabine used for?
Lymphoma/leukaemia
What is methotrexates mechanism of action?
Folate analogue - folate is necessary for purine and pyrimidine synthesis so DNA synthesis cant occur
What type of tumour methotrexate used for?
Lymphoproliferative disorders
What is 5-fluorouracils mechanism of action?
Uracil incorporates into DNA interfering with function/synthesis
What are the sides effects of 5-fluorouracil?
Myelosuppression
Neurotoxicity
What is azathioprines mechanism of action?
Inhibits purine/DNA synthesis
What is azathioprine used to treat?
Lymphoma
Leukaemia
IMPA
What are the main side effects of azathioprine?
Myelosuppression
Liver disease
Pancreatitis
What can you give azathioprine to?
Most dogs
NOT cats
What is hydroxyureas mechanism of action?
Inhibits DNA synthesis
What is hydroxyurea used to treat?
Polycythaemia vera
What is polycythaemia vera?
Tumour of RBC precursors producing excess RBCs
What are some examples of cytotoxic antibiotics?
Doxorubicin
Mitoxantrone
Actinomycin D
What is the most effective agent for most cancers?
Doxorubicin
What is doxorubicin mechanism of action?
Multimodal
eg. DNA intercolation
Alkylation of DNA
Inhibits DNA polymerase
Are some examples of plant alkyloids?
Vincristine
Vinblastine
What is vincristine used to treat?
Lymphoma
What is vinblastine used to treat?
Mast cell tumours
What is the mechanism of action of vincristine/vinblastine?
Inhibits microtubule formation
Interferes with mitotic spindle
What are tyrosine kinase inhibitors used to treat?
Tumours expressing c-kit mutation
eg. Mast cell tumours
What is the main adverse effect of tyrosine kinase inhibitors?
GI toxicity
What are the two tyrosine kinase inhibitors?
Toceranib
Masitinib
What is the main enzyme used as a chemotherapeutic drug?
L-asparaginase
What is the mechanism of action of L-asparaginase?
Destroys circulating asparagine necessary for protein synthesis
What is important about administering L-asparaginase?
Inactivated by rubber so give immediately after reconstitution
from powder
Must be given SC or IP
How do NSAIDs help with chemotherapy?
Induce apoptosis
What are glucocorticoids used to help treat?
Lymphomas
Decrease inflammation and swelling
What are the 4 haematopoietic tumours?
Lymphoma
Lymphoid leukaemia
Myeloproliferative disorders
Myeloma/plasma cell tumours
What is a viral cause of lymphoma?
FeLV
What is a lymphoma?
A neoplastic disease arising from the lymphoreticular system
Where do lymphomas primarily affect dogs?
Lymph nodes
How are lymphomas diagnosed?
Cytology
Histological appearance of lymph node/organ
How are lymphomas classified?
Histological classification and grade
Anatomical area
Immunophenotype - B or T cell
How are lymphomas histologically classified?
Cell size, mitotic rate
What does flow cytometry tell you about the lymphoma?
What surface proteins there are - ‘cluster of differentiation molecules’
Whether it is B cell or T cell
What type of lymphoma is more likely to cause hypercalcaemia?
T cell lymphoma
What anatomical form of canine lymphoma is the most common?
Multicentric - lots of lymph nodes
What type of system do you use to stage canine lymphoma?
WHO
Anatomical site
Stage
Substage
What are the 5 anatomic sites of lymphoma?
Generalised Alimentary Thymic Skin Leukaemia Extra-nodal
What are the stages of the WHO staging system of lymphoma?
Go from only involving one lymph node to generalised to blood/bone marrow involvement
What are the substages of the who staging system of lymphoma?
Clinically well
Clinically unwell
Which type of lymphoma has a poorer prognosis?
T cell
Large cell
Stage V substage b
Male dog
What can be given palliatively to treat lymphoma?
Prednisolone - corticosteroids
What is the most effective drug against lymphoma?
Doxorubicin
Used in CHOP protocol or alone
What is the name for cutaneous lymphoma?
Mycosis fungoides
What is the best treatment for cutaneous lymphoma?
Lomustine and prednisolone
What is the most common anatomical form of lymphoma in cats?
Alimentary
What chemotherapy protocol is better tolerated in cats?
COP
Cats dont like doxorubicin
What is the remission rate for feline lymphoma?
Only 50-70%
What is the median survival time for feline lymphoma?
8 months with COP protocol
What is leukaemia?
Neoplastic proliferation of haematopoietic stem cells
How are leukaemias classified?
Stem cell origin - lymphoid or myeloid
Degree of differentiation
What type of leukaemia has a poorly differentiated form?
Acute leukaemia - poor prognosis
And vice versa
How is leukaemia diagnosed?
Bone marrow evaluation
Blood smear examination
Imaging
Flow cytometry
What type of stem cell origin is more common in leukaemia?
Lymphoid more common than myeloid
What type of degree of differentiation is more common?
Poorly differentiated - acute leukaemia more common
What is a key marker of acute lymphoid leukaemia?
Marked lymphoblast population in the blood and bone marrow
What is aleukaemic leukaemia?
Bone marrow infiltration but absent peripheral lymphoblast
What age is chronic lymphoid leukaemia most common in?
Older patients compared to acute
What type of cells are a marker of chronic lymphoid leukaemia?
Mature lymphocytes - peripheral lymphocytosis
What is a myeloproliferative disorder?
Rare nonlymphoid bone marrow cell disorder
What is the most common myeloproliferative disorder?
Polycythaemia vera
What is the prognosis for chronic myeloproliferative disorders?
Guarded
May undergo a blast crisis - fatal leukaemia phase
What is polycythaemia vera?
Abnormal proliferation of erythroid precursor in the bone marrow
What does polycythaemia vera cause?
Hyperviscosity - high PCV
What are the clinical signs of polycythaemia vera?
Neuro signs
Blindness
Heart failure
What are plasma cell tumours?
When plasma cells/immunoglobulin producing B cell precursor cell lineage transforms into a neoplastic population
What are the 3 most important plasma cell tumours?
Multiple myeloma
IgM macroglobulinaemia
Solitary plasmacytoma
What is a multiple myeloma?
Monoclonal proliferation of malignant plasma B cells
What is a sign of multiple myeloma?
Abnormal amounts of one type of immunoglobulin
What are the clinical signs of multiple myeloma?
Hypercalcaemia
Renal failure
Anaemia
Bone lesions
What do solitary plasmacytomas progress to?
Multiple myelomas
What are histocytes?
Migrate from bone marrow to blood and differentiate to macrophages and dendritic cells
What should the margin be for surgical excision of carcinomas?
1 cm margins - metastasis more of a problem
What should the margin be for surgical excision of sarcomas?
3cm margins - local invasion more of a problem
What should the margin be for surgical excision of round cell tumours?
1-3cm margins - variable
What can excessive tension cause?
Compromise to circulation
Ischaemia
Dehiscence
Necrosis