Basic Oncology Treatment

Question 1

what does cancer treatment choice depend on? (5)

Answer 1

1. tumor type/biologic behavior!!!
2. location of tumor: bladder tumors often not able to treat/access
3. clinical stage of tumor
4. overall condition of the animal: comorbidities
5. owner issues (time, money, other)

Question 2

what are 4 general treatment guidelines

Answer 2

1. you need a definitive diagnosis, cannot be guessing
2. is the treatment working? constant eval
3. treat early: more success when microscopic disease versus gross disease
4. age is not a disease (not too old to treat for cancer!)

Question 3

describe treatment basics (4)

Answer 3

1. most standard cytotoxic treatments injure DNA
2. chemo and radiation therapy target rapidly dividing cells
3. cancer cells are genetically unstable and accumulate mutations to aid their survival, and resistant clones of these resistant cells develop as the tumor grows
4. the tumor can outgrow its blood supply as it gets bigger, so as tumor grows, there is decreased delivery of chemo drugs and decreased proliferation due to poor blood supply

Question 4

what are the 2 broad categories of cancer treatments?

Answer 4

1. local treatments: surgery and radiation therapy
2. systemic treatments: chemotherapy, immunotherapy (FYI), targeted therapy (FYI)

Question 5

describe surgical oncology (4)

Answer 5

1. a chance to cut is a chance to cure! if have a locally invasive metastatic tumor type and can remove it all, good chance of cure (few exceptions: bladder)
2. ALWAYS submit the entire excised tissue and request EXTENDED report, communicate with pathologist and call with any questions (if owner not want to send off, preserve for when they do but notate tissue orientation before send off or preserve)
3. mark cut borders using inking system or sutures; avoid using drains (could make it a bigger cancer field than what started with)
4. define your goal: could be any of 4
   -getting a diagnosis
   -attempting a cure
   -debulk to microscopic disease (take away gross aspects so other treatment modalities work better)
   -palliation

Question 6

describe incisional versus excisional biopsy

Answer 6

incisional:
goal: diagnosis
-removal of a piece of the tumor
-once diagnosis is obtain, can then plan treatment which may include excisional biopsy

excisionial:
goal: diagnosis PLUS treatment
-removal of entire tumor +/- margins
-curative in some cases

Question 7

what are some techniques to obtain an incisional biopsy? (9)

Answer 7

1. FNA
2. wedge cut
3. tru-cut: like an FNA but with a bigger needle to get a chunk of tissue
4. punch
5. endoscopic
6. traumatic catheterization
7. image-guided
8. laparoscopic or thoracoscopic
9. surgical exploratory

Question 8

describe 5 important aspects of biopsy

Answer 8

1. take multiple samples
2. leave biopsy tract in area that can easily be resected with tumor
3. do not cross tissue planes
4. small samples in cassettes
5. give good description and history

Question 9

describe curative intent surgery

Answer 9

1. goal = removal of ALL cancer cells
   -2-3cm margins (cut 2-3 to target 0.5cm microscopic margin) and at least 1 tissue plane deep
   -never shell out a tumor/leave a pseudocapsule
   -first excision is best chance of a cure (most normal anatomy around it)
2. prior to curative intent surgery, consider
   -stage of disease (has cancer spread)
   -biologic behavior of tumor
   -likelihood of excision

Question 10

describe a debulking surgery

Answer 10

1. goal is removable of all VISIBLE cancer cells, leaving only microscopic disease to improve efficacy of other treatment moadlities
2. used on areas where cannot get good margins (legs, etc.)

Question 11

describe palliative surgeries

Answer 11

1. goal is to alleviate clinical signs and improve quality of life
2. must consider morbidity of surgery and cost and weight against the expected benefit

Question 12

describe radiation therapy (5)

Answer 12

1. RT = ionizing radiation
2. RT causes direct/indirect DNA damage to result in cell death
   -two-thirds: indirect
   -one-third: direct
3. fraction = 1 radiation dose; absorbed dose of radiation measured in Gray (Gy)
4. proliferating cells are radio-sensitive; normal tissue tolerability limits the total radiation dose
5. need to define goal:
   -curative intent/definitive RT: most common and for microscopic disease, can cure or long term control, hella expensive, acute toxicity expected, avoid late toxicity
   versus
   -palliative RT: for pain control or relief of clinical signs

Question 13

what is the most common type of radiation therapy used? describe (3)

Answer 13

external beam RT (EBRT)

1. applied from a distance via linear accelerators
2. superficial vs. deep penetration: can control level
3. patient under general anesthesia: must be in same position every time and no one else can be in the room

Question 14

describe strontuim pleseotherapy (radiation therapy)

Answer 14

1. local, small fields
2. sueprficial (2-3mm)
3. typically delivered as a single treatment
4. uses: eyelids (squamous cell carcinomas), noses
5. may be able to just get away with sedation versus general anesthesia

Question 15

are side effects of radiation common? describe acute and late

Answer 15

side effects uncommon! radiation itself should not make animal sick (unless GI tract in field of radiation)

acute:
-occur during or within weeks of treatment in rapidly proliferating tissues and resolve a couple weeks post treatment

late side effects:
occur within months to years of treatments in rarely proliferating tissues (brain, nerve cells), do NOT resolve, and may result in mortality

Question 16

describe chemotherapy generally

Answer 16

1. MOA varies: can damage DNA, inhibit protein synthesis, or inhibit cells division (target rapidly dividing cells)
2. know MOA and ALL side effects before use!!
3. systemic treatment for highly metastatic tumors
4. most common route of admin is IV
5. chemo is calculated based on mg/m2 basis (more accurate assessment of body surface area bc such a narrow window of safety, use a chart or an app), NOT mg/kg

Question 17

describe chemotherapy safety (4)

Answer 17

1. chemo is mutagenic, carcinogenic, and teratogenic
2. avoid unnecessary exposure
3. administer in quiet, low traffic area
4. PPE; be aware of patient excretions, will be excreting toxic metabolites!

Question 18

describe chemotherapy side effects

Answer 18

1. chemo is well tolerated, less than 5% of patients require hospitalization
2. BAG side effects; caused by any/most chemos
   -B = bone marrow suppression: cells with shorter half lives are most affected (neutrophils, so neutropenia is most common), followed by platelets, and followed rarely by RBCs, so always check CBC before and then 5-7 days after
   -A = alopecia, but most patients have fur not hair so less affected, hair color could change, cosmetic only
   G = GI toxicity: rapidly dividing cells in the crypts, mature up into villi, die off
   -decreased appetite, V/D for a couple days after treatment
   -NPO and anti-emetics and hospitalization if becoming dehydrated