Intro to Cancer

  • Cancer = Uncontrolled cellular growth
    • May manifest as either a local tissue invasion or a distant metastases
  • Incidence and mortality trends
    • Incidence:  Prostate & breast cancer are the most common for men & women, followed by lung as 2nd for both & colorectal as 3rd for both
    • Mortality:  Lung is the most common cause of death for both men & women, prostate & breast are 2nd, colorectal is again 3rd
  • Principles of tumor growth
    • Started by a carcinogen initiator (may be chemical–asbestos, benzene, chemo drugs; physical–UV, radiation; or biological–HPV)
    • These initiators may affect oncogenes (affect tyrosine kinases resulting in overexpression in cellular proliferation) or tumor suppressor genes (mutations in p53 tumor suppressor gene)
      • Growth fraction:  the proportion of tumor cells actively dividing (the smaller the tumor, the higher the growth fraction)
      • Doubling time:  time required for a tumor to double in size (usually 2-3 months); as the tumor gets larger, the doubling time lengthens
      • Tumor burden:  amount of tumor burdening the patient (usually lethal at around 1kg)
      • Cell kill hypothesis:  each round of chemo kills a constant % of cancer cells (can’t ever get to 0 with chemo alone, body has to take over at some point)
    • Metastases:  spread of neoplastic cells from the primary tumor site to distant sites where these cells give rise to new lesions
      • Tumors are constantly shedding cells that may or may not find suitable environments (not all cancers can live anywhere in the body) and result in angiogenesis
      • Malignant cancers are far more likely to metastasize & differentiate, aren’t encapsulated, high growth rate & recurrence is common
  • The American Cancer Society’s 7 cancer warning signs
    • CAUTION:
      • Change in bowel or bladder habits
      • A sore that does not heal
      • Unusual bleeding or discharge
      • Thickening or lump in breast or elsewhere
      • Indigestion or difficulty in swallowing
      • Obvious change in a mole or wart
      • Nagging cough or hoarseness
  • Staging systems for cancer diagnosis
    • TNM system
      • T:  tumor (T1-T4)
      • N:  Node (N0-N3)
      • M:  Metastases (M0-M1)
    • Numerical System
      • Stage 1:  localized tumor
      • Stages 2/3:  local & regional extension of the disease
      • Stage 4:  Presence of distant metastases
  • Benefits of a staging system
    • TNM system is the nomenclature for all primary sites & has worldwide use & acceptance
    • Numerical system is easier to understand
  • Treatment Options
    • Surgery:  plays a major role in diagnosis & treatment;  treatment of choice for early diagnosed solid tumors
    • Radiation:  mainstay in cancer management (> 50% of pts receive it)
    • Biological therapies:
      • Immunotherapy (interferons & interleukins) stimulate host immune system
      • Targeted therapies (MABs & TK-Inhibitors) & Vaccines
    • Chemo:
      • Used alone (primary) for leukemias
      • Used for symptom control/reduce tumor size (Palliative)
      • Given after primary treatment (adjuvant) to clean up micrometastatic disease
      • Used preoperatively to shrink tumors (neoadjuvant) so they can be surgically removed
      • Single agents usually aren’t effective for treatment/cure–need to combine agents in order to decrease toxicity & resistance
  • Definitions
    • Cure = free of disease for 5 years (w/ the exception of breast cancer & melanoma)
    • Complete response = complete disappearance of cancer (no evidence of new disease for at least 1 month after treatment)
      • Complete response is not the same as cure
    • Partial response:  greater than or equal to a 30% decrease in tumor size (& no evidence of any new disease for at least 1 month)
    • Stable disease:  tumor size neither grows nor shrinks
    • Progression:  20% increase in tumor size (development of any new lesions while receiving treatment)
    • Clinical benefit response:  subjective response that allows for the assessment of quality of life (ex. decreased pain allows you to decrease pain meds)

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