Cancer Overview

Cancer = Uncontrolled cellular growth. May manifest as either a local tissue invasion or a distant metastases

The 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

The 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 a 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

Different Treatment options for cancer

  • 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

Defining complete response, partial response, stable disease and progression of cancer

  • 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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