Radiation Oncology Flashcards
Define: tumor, cancer, benign, malignant
Tumor: abnormal mass of tissue that results when cells divide more than they should or do not die when they should. May be benign or malignant.
Cancer: diseases in which abnormal cells divide without control and are able to invade other tissues.
Benign: NOT cancerous. Can cause local problems but do not spread to other parts of the body. If removed, typically does not come back.
Malignant: Cancerous/has inherent risk of recurrence and ability to invade other tissues. Spreads to other parts of body causing metastasis.
4 Hallmarks of Cancer
1) Inappropriate cell proliferation: increased production, decreased death.
2) Neoangiogenesis.
3) Invasion with metastasis
4) Genomic instability: do not have repair systems for cell damage. Also have capacity to mutate such that they will no longer be sensitive to tx’s.
Mechanisms of cancer spread
1) direct invasion
2) Lymphatics
3) Hematogenous: via bloodstream
4) Transcoelomic: pleural, pericardial, peritoneal.
Describe TNM staging
Tumor: size and extent of spread of primary tumor. Correlates with direct invasion.
Node: spread to LN via lymphatics.
Metastasis: spread to other parts of body, associated with hematogenous spread.
Benefits of staging
Communication, treatment guidance, prognostication, comparison of results over time, clinical trial standardization.
Difference between terms clinical stage, pathologic stage and tumor grade.
Clinical stage: based on PEx, imaging, lab tests.
Pathological stage: pathology of primary tumor or from surgical reports.
Stage: tumor extent, nodal status, spread.
Grade: how the cells appear (normal/abnormal differentiation from primary site).
Differentiate the goals of Ca tx
Radical therapy; curative intent, complete ablation.
Adjuvant: Curative w/ intent to address microscopic disease and reduce risk of recurrence.
Palliative: To reduce or prevent symptoms.
Describe the tx options for Ca and considerations w/ each modality: Surgery vs systemic vs radiation
Surgery: radical treatment for most solid tumors. In order to proceed, pt must be good candidate, need to assess whether it is possible to do complete resection and examine whether there are mets. Consider mborbidity of surgery and whether there are alternative effective tx (e.g. brachytherapy for prostate Ca is as effective as Sx).
Systemic therapy (chemo): radical (curative) tx for most hematologic cancers. Must consider pt medical/psych comorbidities, social situation for self care. Tumor/cancer must be chemosensitive and assess tumor stage (may use as adjuvant).
Radiation: radical for some solid cancers +/- chemo. Consider possible pt contraindications (e.g. ability to show up from center or lie still/flat for tx). Tumor must be radiosensitive. Consider toxicity and availability of tx (e.g. the younger you are, the higher your risk of toxicity).
What are the 1) patient factors, 2) tumor factors and 3) treatment factors that influence treatment decision.
1) Pt factors: performance status (ecog level), patient preference.
2) Tumor factors: type of cancer, stage, symptoms.
3) Tx factors: availability and effectiveness of tx, potential toxicity.
What are the ecog levels
0: no restrictions
1: able to work, minor restrictions (e.g. unable to do very strenuous activity)
2: unable to work, spend >50% of awake time up and performing daily activities. Ambulatory + capable of all self-care.
3: >50% of wake time spent resting, capable of limited self care.
4: Confined to bed, completely disabled.
5: dead
Basic principles of radiation therapy
What: radiation is high energy ionizing photons that cause damage to cellular DNA. Because cancer cells have difficulty repairing cell damage they die while normal cells are able to repair themselves.
Treatment: divided into fractions, a series of small daily treatments that allows time for normal tissues to heal in between sessions. Total dose = # fractions x daily dose.
CT imaging used prior to tx for planning purposes, also used to routinely check set up during tx.
Types of radiation therapy (choice depends on type of tumor):
1) External beam radiation therapy: radiation given from source outside the body.
2) Brachytherapy: direct application of radioactive source into/adjacent to tumor. Benefit = radiotx is delivered at closest pt to tumor as possible.
3) Isotope tx: IV/oral ingestion of radioactive isotopes that concentrate in cancer tissue (e.g. Iodine-131 for thyroid cancer).
Contraindications to radiotherapy
Previous radiation, pregnancy, connective tissue disorders.
Common acute and late SE of radiation:
General: radiation SE dictated by area the beams traverse. Toxicity is affected by normal structures in the radiation field.
Acute SE (within 6 months): Due to acute inflammatory reactions. Main is moist skin desquamation (sunburn appearance to skin that is dose dependent).
Late SE (>6 months - years): due to fibrosis of connective tissue and obliteration of small blood vessels. Changes in skin pigmentation (hypo/hyper), fibrosis w/ loss of elasticity, telangiectasia.
4 key oncologic emergencies
Def'n radiation oncologic emergency: reversible threat to organ function requiring radiation treatment within a few hours of diagnosis. #1 Emergency: Spinal cord compression. Urgencies: SVCO, brain mets, malignant hemorrhage.
Approach to diagnosis, key features and mgmt strategies for SC compression
What: compression of the dural sac ands its contents by an extradural tumor mass. On imaging, look for indentation of the thecal sac at the level of the clinical features.
Thoracic (60%) > lumbosacral (30%) > cervical spine (10%)
Note that SC ends at L1/2, thus compression below this = cauda equina syndrome.
Spinal mets may cause compression via multiple mxn’s: 1) growth and expansion of vertebral bone met into epidural space, 2) neural foramina extension by paraspinal mass, 3) destruction of the vertebra resulting in collapse and displacement of bony fragments into epidural space. Knowing mxn will affect mgmt approach.
Compression –> vascular damage: increased arteriole pressure, venous plexus compression and reduced capillary flow. Get SC edema which causes white matter ischemia/infarct and potential permanent cord damage.
Symptoms:
90% present with back pain as the first symptom.
Sensory symptom = PAIN. Precedes other neurological deficits by months, is localized (e.g. should be able to pt with single finger), most severe over involved vertebrae, radicular around trunk/limb (burning, shooting pain), numbness/parasthesias (late finding).
Motor: weakness. May be UMN or LMN depending on area being compressed.
Imaging: MRI = test of choice if high suspicion.
Mgmt:
early referral to improve pain relief and restore function.
Dexamethasone: helps retain motor function, give 8 mg BID as standard. Works very well.
Surgery: provide functional relief + physiological stability. Indications include spinal instability/bony compression, remote Ca Dx, neurological progression on RT or prior radiation.
Radiotherapy: can be used to improve pain and maintain ambulation. Should be started within 24 hrs. Indicated if medically inoperable, ambulatory, diffuse disease or post-surgical. 5-10 # at involved site.
Chemo is not first line.
