Strategies of Cancer Treatment & Prevention (Pence) Flashcards
Approaches to local tx of cancer:
- surgery
- radiation
- ablation (cryosurgery, radiofrequency)
(tx can be combined, ex: surgery and/or ablation OR sugery + radiation)
Approaches to systemic cancer tx:
- chemotherapy (cytotoxic, hormone, biologic)
Things to consider when pursuing local therapy:
- can you remove all of the cancer
- are there limited options for systemic therapy
- if cure cannot be achieved, could treatment palliate
What are the common cancers tx w/ local therapy?
- sarcomas
- non-melanoma skin cancer
- in situ carcinomas
What is the timeline of tx in terms of adjuvant therapy?
(optimal therapy requires multiple tx modalities)
- surgery first provides “cytoreduction”
- after surgery: radiation and systemic therapy (often chemo)
What is the timeline of tx in terms of neoadjuvant therapy?
(usually applied to large tumors)
- surgery is not as effective initially d/t size of tumor
1. cytoreduction provided first (chemo/rads)
2. surgery for gross reduction after initial cytoreduction
3. after surgery, more adjuvant therapy (chemo/rads)
What is the sequential order of cancer therapies and what is their specific purpose?
- neoadjuvant: reduce primary tumor size, eliminate cancer cells that spread to other locations
- primary: gross elimination of tumor
- adjuvant: eliminate remaining cancer cells
When is surgery not indicated for cancer tx?
- metastatic dz removes advantage of surgery
- leukemia/lymphoma
- systemic therapy is so effective that surgery is unnecessary
What are the 3 most common types of radiation therapy?
- external beam radiation (intensity modulated radiotherapy (IMRT))
- brachytherapy
- systemic radionucleotides
- type of radiation therapy
- linear accelerator delivers direct radiation beams to affected sites
external beam radiation
- subtype of external beam radiation
- takes a 3D image of patient and mass
- reduces amount of radiation exposure to patients and healthy tissue
- used in instances where the tumor is wrapped around important structures (ex: aorta)
intensity modulated radiotherapy (IMRT)
- subtype of external beam radiation
- commonly used in primary brain tumors
- image of the brain is generated and the vectors of radiation are mapped out to spare healthy tissue within the brain
cyberknife
- type of radiation therapy
- very localized high-dose therapy delivered continuously for a prolonged time through implanted devices
- most commonly used in prostate cancer
- in prostate cancer, a needle is inserted into the prostate where radioactive seeds are implanted
brachytherapy
- type of radiation therapy
- radioactive substance is injested, these molecules are absorbed through digestive tract to bloodstream, the part of the body that is targeted will absorb the molecules, the radiation destroys cancer and normal cells
- most commonly used in thyroid cancer (radioactive iodine, aka I^131, for thyroid cancer and non-cancerous dz’s of thyroid)
*people undergoing this therapy have to be isolated for ~4 days b/c they are radioactive, their body fluids also have to be disposed of properly d/t their radioactive nature*
systemic radionucleotides
When should radiation therapy be used in cancer?
- part of adjuvant therapy
- part of neoadjuvant therapy
- when surgery is contraindicated (patient of advanced age w/ prostate cancer)
- to palliate: spinal metastasis to prevent cord compression/alleviate neurologic sx, ENT carcinoma to prevent suffocation, pelvic sidewall to prevent pain
What are the different types of systemic cancer therapies?
- conventional: cytotoxic chemotherapy (does not discriminate between healthy and malignant cells)
- targeted agents: hormonal, biologics (tumor mediated, immuno-regulatory mediated, Ab conjugates)
What is the importance of considering the therapeutic index and therapeutic window in conventional systemic cancer tx?
- the higher the therapeutic index (TD50/ED50), the better the drug (this means the drug has a high toxic dose and low effective dose)
- cytotoxic chemotherapies (the conventional systemic cancer tx) generally have low therapeutic indexes, meaning there will almost always be adverse side effects
- the main goal is to kill as many cancer cells while sparing healthy cells, this is why chemo is given in cycles and days to allow normal cells time to recover
- it is important to know what side effects (even on what days) may occur to ensure proper management of sx and any prior/post tx diagnostics that may need to be obtained
What are the types and indications of targeted systemic cancer therapies?
- hormone: is tumor dependent on hormone stimulation (i.e. breast, prostate), look at receptor status and inhibit
- growth factors: is tumor dependent on growth factors (i.e. epidermal growth factor, vascular endothelial growth factor), look at receptor status and inhibit
- antigens: are there antigens that can be targeted (i.e. CD20 for B-cell lymphomas), use recombinant Abs (Rituximab)
- immune checkpoints: is PD-1 or CTLA on tumor cells diminishing our tumor immunity, use immune checkpoint inhibitors
- a type of systemic cancer therapy
- T-cells (autologous or allogenic) are manipulated ex vivo (often by exposure to a virus) to express a binding domain for a tumor-associated antigen (customized) w/ a transmembrane domain and an intracellular signaling domain that intensifies the immune attack against tumor cells
- not readily available as tx currently, only been approved for ALL
- causes cytokine release syndrome (CRS) that occurs in 80%: causes high fever, flu-like sx, and even death in some cases (CRS can be tx w/ Toluzimab)
CAR-T therapy
(chimeric antigen receptor therapy)
General difference between A/B grading and C grading for USPSTF grading:
- grade A and B are generally recommended
- grade C you need to informed consent from patient
How beneficial is PSA in prostate cancer screening?
- high false positive rate
- serum testing increases in many benign and inflammatory conditions (prostatitis), also milking the prostate (DRE) can increase PSA
- for age 55-59 screening w/ PSA (PLCO trial): prevented 1.3/1000 men screened over 13 years, prevented 3 cases/1000 men of metastatic prostate cancer, ~2/3 men underwent bx for elevated PSA that did not have prostate cancer (aka this is doing more harm than good)
Guidelines for pap smear screening:
- cytology
- excellent at detecting pre-malignant and malignant cells
- start at age 21 (almost unanimous across guidelines (ACS says 25)), and then repeat every 3 years
- stop at age 65, unanimous across guidelines
- for 30-64 age group, guidelines are not as clear, in general: pap alone = q3 years; pap+HPV = q5 years (f/u will be more frequent for positive tests)
- USPSTF recommendations: <21 y/o grade D (not rec), 21-29 years grade A, 30-65 years grade A, >65 years grade D
How to perform self breast exam:
- allows early familiarity w/ subtle changes to breast tissue, can be started at early age, frequency of every month
- check the axilla, look for skin changes, avoid checking prior to/during menstrual cycles, find a system that helps you remember to do it
Screening/USPSTF grade and prevention cheat sheet:
*note under cervical cancer screening HPV testing should be included*
