Principles of cancer (1) Flashcards
Cell division cycle
The cell goes through different phases as it divides (G0, G1, S, G2, and M phase)
this is important to consider because some drugs will be non specific (kill the cells at any point of the cycle), but some drugs will be cell cycle specific- and only kill drugs when they are at a certain point in the cycle
Micrometastasis
metastasis that cannot be detected by imaging
responsible for relapse
This is why we need to give chemotherapy systemically
(because there may be metastasis in places we are not aware of)
If we could pick up on these, we could treat cancer even better
Mechanism of metastasis (4)
- Hematogenous spread
-cells of primary tumor penetrate into blood vessels, spread through blood stream - Lymphatic spread
-cells of a primary tumor penetrate into lymphatic vessels - Cerebrospinal dissemination
-cells of primary tumor penetrate CSF directly or reach CSF through blood stream (cross BBB) - Trans-abdominal spread
-cells of primary tumor penetrate other organs within the abdominal cavity
Warning signs for adults (CAUTION)
C - change in bowel habits (colorectal cancer)
A - a sore that dose not heal (skin cancer)
U - unusual bleeding or discharge (lymphoma/leukemia)
T - thickening or lump in breast or elsewhere (breast cancer)
I - indigestion or difficulty swallowing (esophageal/throat cancer)
O - obvious change in wart or mole (skin cancer)
N - nagging cough or hoarseness
Warning signs for pediatrics (CHILDREN)
C - continued unexplained weight loss
H - headaches with vomiting in the morning
I - increased swelling or persistent pain in bones/joints
L - lump/mass in abdomen, neck or elsewhere
D - development of whitish appearance in the pupil of the eye
R - recurrent fevers not caused by infections
E - excessive bleeding/bruising
N - noticeable paleness or prolonged tiredness
What is the number 1 type of cancer in kids?
Leukemia
____________ must be staged prior to ________________
Solid tumors must be staged prior to initiation of treatment
(stages provide prognosis and guide treatment)
Solid tumor staging
Stage 1 - localized tumor
Stage 2 - spread to local lymph node near mass
Stage 3 - spread to distant lymph node away from mass
Stage 4 - spread with lymph node involvement + metastases
3 treatment modalities of cancer
- Surgery
- Radiation
- Chemotherapy
Surgery
Treatment of choice for most early stage solid tumors
Local treatment only
Usually combined with radiation and/or chemotherapy (to make sure all cancer cells are removed)
-The goal is to remove the tumor with negative margins (remove all cancer cells)
May be palliative (not necessarily curative in late stages)
Neoadjuvant vs adjuvant therapy with surgery
Surgery is usually combined with chemotherapy and/or radiation to ensure negative margins (removal of all cancer cells)
This can be done before, or after the surgery …
Neoadjuvant therapy is when the chemo/radiation is done prior to surgery
Adjuvant therapy is when the chemo/radiation is done after surgery
Radiation
Local treatment only
Usually combined with surgery and/or chemotherapy
May be palliative (not necessarily curative in late stages)
Radio-sensitizing chemotherapy is used to radiosensitize the tumor
Radiosensitizing chemotherapy
Low doses of chemotherapy given to radiosensitize a tumor (make cancer cells more vulnerable to radiation therapy)
Agents commonly used:
Cisplatin
Fluorouracil
Gemcitabine
Chemotherapy for solid tumors
Administered to eradicate cancer cells - systemic circulation (good to get rid of metastasis)
Can be given orally, intravenously, or intrathecally
Given as a regimen - different agents that are used throughout a cycle
-a cycle is the block of time during which the regimen is given
-the cycle is usually 21 days - different drugs part of the regimen will be given throughout and then there will be a period of time during which no chemotherapy is given (chemo kills normal cells too, so we hold therapy and wait for counts to normalize then start the cycle again)
-usually for solid tumors patient undergoes 4-6 cycles on average
How does chemotherapy differ for hematologic malignancies? (leukemia)
The terminology differs - instead of cycles, there is … induction, consolidation, and maintenance therapy
More aggressive up front
In general chemotherapy works best during which time?
When cells are moving faster through growth phases -
this occurs before 10^5 is reached
As the tumor gets bigger, (reaches 10^9 when you can clinically detect it) - at this point it is getting big and may get into surrounding tissue and metastasize - chemo will not work as well
And if you allow it to keep growing (without treatment) , the tumor will eventually plateau - it will outgrow the nutrient and blood supply there, and it will metastasize
Solid tumors are pretty slow growing in general (double in 2-3 months) compared to leukemia/lymphoma (double in days) - which is why the therapy for those is more aggressive
Cell kill hypothesis
Chemotherapy works to kill cancer cells, each cycle kills ~90%, but never reaches zero cancer cells
The hypothesis is you give multiple cycles, it will get less and less and then eventually the immune system takes care of what’s left
But there are flaws with this hypothesis
-assumes all cancers are equally responsive to chemo
-assumes that metastases do not occur
-assumes that resistance to chemo does not exist
Because of these limitations this hypothesis is not used much anymore - focus on the size/staging to figure out course of action when patient is diagnosed
Cell phase specific vs non cell phase specific chemo administration considerations
Cell cycle phase specific chemo…
-only kills cells when they are in a particular phase of the cell cycle
-Schedule dependent dosing … give continuous infusions or multiple repeated doses - so that the agent is available in the body for longer period of time - whenever the cells go into that specific phase (since they won’t all be there at the same time)
Cell cycle phase non specific chemo…
-has cell killing activity in multiple phases
-Dose dependent dosing … give larger doses
Factors that effect response to chemotherapy (6)
- Tumor burden (larger tumor)
- Cancer cell heterogenicity (homogenous populations of cells are easier to kill)
- Drug resistance (can be due to inherited gene or mutations can occur during therapy)
- Dose response
- Location of disease
- Patient specific factors