Unit 1


Fundamental Definitions of Cancer

  • Definition of Cancer:

    • A collection of over 200 different types of diseases characterized by uncontrolled cell division.

    • Caused by changes to DNA.

    • Multi-hit theory: several changes required to develop cancer.

  • Localised Cancers:

    • Can invade surrounding tissues or metastasize to other sites.

Cancer Incidence and Mortality

  • Statistics:

    • Every 2 minutes, someone in the UK is diagnosed with cancer.

    • Approximately 390,000 new cancer cases in the UK annually (2017-2019).

    • Excludes non-melanoma skin cancer (NMSC).

    • Around 155,000 new NMSC cases in the UK annually (2016-2018).

    • Approximately 167,000 cancer deaths in the UK annually (almost 460 per day).

    • More than 1 in 3 people in the UK expected to develop cancer in their lifetime.

    • Cancer can develop at any age, but less than 1% of cancers occur in children (aged 0-14).

    • Over 60% of cancer diagnoses occur in individuals aged 65 and over.

    • OECD projects £14.4 billion increase in UK health spending due to cancer by 2050.

Differences between Benign and Malignant Neoplasms

Comparison Table

Characteristic

Benign

Malignant

Encapsulation

Often encapsulated

Non-encapsulated

Differentiation

Well differentiated

Poorly differentiated

Mitotic Rate

Low mitotic rate

High mitotic rate

Invasiveness

Non-invasive

Invasive

Metastasis

Non-metastatic

Metastatic

Cancer Types and Their Classifications

Common Types of Cancer

  1. Carcinoma:

    • Origin: Epithelial tissues (skin, internal organs)

    • Subtypes include:

      • Adenocarcinoma

      • Basal Cell Carcinoma

      • Squamous Cell Carcinoma

      • Transitional Cell Carcinoma

  2. Sarcoma:

    • Origin: Connective/supportive tissues (bone, cartilage, fat, muscle, blood vessels)

  3. Leukaemia, Lymphoma & Myeloma:

    • Origin: Hematopoietic (blood-forming tissues)

  4. CNS Tumors:

    • Affect brain and spinal cord (e.g., glioma)

  5. Blastoma:

    • Commonly affect children, often originates from precursor cells (e.g., retinoblastoma)

Other Cancer Information

Incidence and Mortality Insights

  • Non-Melanoma Skin Cancer (NMSC):

    • 155,985 new cases reported (2016-2018, UK).

    • 918 deaths annually from NMSC; accounted for <1% of cancer deaths in the UK.

    • NMSC incidence under-reported due to incomplete data records.

  • Most Common Cancers (Excluding NMSC):

    • 4 cancers account for >50% of all cases:

    • Breast

    • Prostate

    • Lung

    • Bowel

    • Statistics indicate that thyroid and liver cancers have the fastest increasing incidence rates among both genders in the UK.

  • Mortality Analysis:

    • Lung, bowel, breast, and prostate cancers account for nearly half (45%) of all cancer deaths within the UK (2017-2019).

Cancer Survival Rates

  • Statistical Findings:

    • 50% of individuals diagnosed with cancer in England and Wales survive for 10 years or more (2010-11).

    • Survival rate varies significantly among cancer types, from 98% (testicular cancer) to only 1% (pancreatic cancer).

Age-Standardised Net Survival

  • Variability exists in survival rates across multiple cancers.

  • Ten-year survival statistics indicate significant improvements for several cancer types but less improvement seen in specific cancers (e.g., stomach, brain, esophageal).

Global and Ethnic Trends

  • Global Context:

    • Cancer is the 2nd leading cause of mortality globally (after cardiovascular diseases).

  • Ethnic Group Variation in Cancer Incidence (England, 2013-2017):

    • Lower overall incidence in Asian and Black ethnic groups compared to White ethnicity.

    • Lung, bowel, breast, and prostate cancers are the most prevalent across all groups, with variations observed (e.g., prostate cancer being more frequent in Black populations).

Cancer Aetiology and Prevention

Aetiological Agents

  • Genetic Factors:

    • Includes inherited predispositions (e.g., XP, retinoblastoma, BRCA1).

  • Chemical Agents:

    • Primarily tobacco exposure.

  • Radiation:

    • Radon gas and other exposures.

  • Biological Factors:

    • Infections (e.g., Human Papillomavirus associated with cervical cancer).

  • Inflammation:

    • Conditions leading to colon, pancreatic, ovarian cancers.

  • Environmental Factors:

    • Link between occupational exposure and carcinogenesis seen historically (e.g., studies by Sir Percival Pott).

Lifestyle Factors Contributing to Cancer

  • Smoking:

    • Causes 30-40% of all cancer deaths in the UK.

    • Specific links with cancers of the lung (86%), larynx (79%), mouth (65%), bladder (37%), and kidney (24%).

Prevention Strategies

  • Lifestyle Changes:

    • Over 40% of cancers could be prevented through:

    • Quitting smoking

    • Maintaining a healthy weight

    • Limiting alcohol intake

    • Balanced diet and physical activity

    • Vaccination against infections like Hepatitis B and HPV

  • Screening Programmes:

    • Current UK screening programs target breast (mammograms), bowel (fecal immunochemical tests), and cervical (HPV tests) cancers.

Summary of Key Points

  • Cancer incidence is heavily age-dependant.

  • Untreated cancers can be fatal, hence early diagnosis is crucial.

  • The integration of knowledge about aetiology, prevention, and screening can significantly improve cancer burden management.

Appendix A: Definitions

  • Tumor: An abnormal mass of tissue that results from uncontrolled cell division, can be either benign or malignant.

  • Neoplasia: The state of cancerous growth characterized by uncontrolled proliferation of abnormal cells that persist beyond the stimulus.

  • Differentiation: Describes how closely neoplastic cells resemble normal cells, classified as well, moderately, or poorly differentiated.

  • Anaplasia: Lack of differentiation; a key characteristic of malignancy.

  • Hyperplasia, Hypertrophy, and Metaplasia: These terms refer to reversible conditions of increased cell number, cell size, and replacement of one cell type with another, respectively.