Cancer

Introduction A group of more than 200 diseases

characterized by uncontrolled and unregulated growth of cells

In NZ 14,808 new cases of cancer 1 in 3 men and 1 in 4 women will be

affected by age 75yrs Most common cause of death in NZ (29%

of deaths overall)

Cancer

Most common cancers causing death in males are lung, prostate and colorectal

Most common cancers causing death in females are breast, lung & colorectal

Cancer rates for Maori & non Maori are similar but mortality rates are 51% (males) and 78%(females) higher for Maori

5-year survival rate is now 62% for those who are disease free, in remission, or under treatment

5-year survival rates do not include the number of people who are “cured” of cancer

Defect in Cellular Proliferation (process by which cells divide & reproduce)

Cancer cells are characterized by the loss of contact inhibition – have no regard for cellular boundaries Grow on top of one another and on top of or

between normal cells Cancer cells divide indiscriminately and

haphazardly – sometimes they produce more than 2 cells at the time of mitosis

Defect in Cell Proliferation

In most situations, cancer cells multiply at the same rate as the normal cells from which they originate

The difference is that proliferation of the cancer cells is indiscriminate and continuous

Because of this there is continuous growth of a tumour mass

Defect in Cellular Differentiation

Cellular differentiation (the development of specific & distinctive features in cells) is normally an orderly process

Protooncogenes- Normal cellular genes that are important

regulators on normal cellular processes- Mutations that alter their expression can

activate them to act as oncogenes (tumour-inducing)

Neoplasms

Characterised as:

1. Benign neoplasms

2. Malignant neoplasms

Major difference between malignant & benign neoplasms is the ability of malignant tumour cells to invade and metastasize

Benign Neoplasms

Well differentiated (specific & distinctive features of cells are well developed).

Cells resemble the cells of tissue of origin. Well-defined fibrous capsule Characterized by slow, progressive rate of growth. Tumours grow by expansion Metastases absent Recurrence unusual Do not usually cause death unless they interfere with vital

functions because of location e.g.. Benign cranial tumour compressing brain structures

Malignant Neoplasms

Tend to grow rapidly, spread widely, & kill regardless of original location

Able to metastasize Because of rapid growth, they compress blood vessels & outgrow

their blood supply causing ischaemia & tissue necrosis Rob normal tissues of essential nutrients Liberate enzymes & toxins that destroy normal & tumour tissue Infiltrative and expansive Frequent recurrence Moderate to marked vascularity Rarely encapsulated Cells abnormal; become more unlike parent cells

Effects on Body Function with Cancer Growth

Altered function of involved tissue Bleeding & haemorrhage Ulceration, necrosis & infection of tumour area Obstruction of hollow organs or pathways Effusion in serous cavities Increased risk of vascular thrombosis Anaemia Bone destruction

Effects (cont.)

Hypercalcaemia Pain Cachexia – weight loss & wasting of body fat

& lean protein Inappropriate hormone production (e.g. ADH

or ACTH secretion by cancers such as bronchogenic carcinaoma)

Cachexia

Advanced Breast Cancer

Cancer of Kidney

Ascites – Liver Cancer

Development of Cancer

Carcinogens – cancer-causing agents capable of producing cellular alterations

Can be chemical, environmental, immunologic, viral, or spontaneous in origin

Some genetic abnormalities increase the susceptibility of individuals to certain cancers

Hereditary predisposition in approx 50 types of cancers e.g. breast cancer

Process of Cancer Development

Fig. 15-3

Metastasis

The spread of cancer from the initial or primary site to a distant site

Some metastasize early e.g. pre-menopausal breast cancer

Others spread regionally and rarely metastasize e.g.. BCC of skin

Certain cancers have an affinity for a particular tissue or organ as a site of metastasis, others are unpredictable e.g. melanoma

Metastasis (cont.)

Certain cancers (‘seed’), such as ovarian cancer, require a particular site for proliferation (‘soil’)

Most frequent sites for metastases are lungs, brain, , bone, liver & adrenals

Metastasis

Metastasis process begins with rapid growth of primary tumour Development of its own blood

supply is critical for survival Tumour angiogenesis is

formation of blood vessels within the tumour

Melanoma Metastases

Progression of Cancer Metatases

Role of Immune System

Immune response is to reject or destroy cancer cells if perceived as non-self May be inadequate as cancer cells arise

from normal human cells Some cancer cells have changes on their

surface antigens Tumor-associated antigens (TAAs)

Role of Immune System

Response to TAAs is termed immunologic surveillanceLymphocytes continually check cell

surfaces and detect and destroy cells with abnormalities

Involves cytotoxic T cell, natural killer cells, macrophages, and B lymphocytes

Role of Immune System

Escape mechanisms by which cancer cells evade immune systemSuppression of factors that

stimulate T cellsWeak surface antigens allow cancer

cells to “sneak through” surveillance

Role of Immune System

Development of tolerance of immune system

Suppression of immune response to products secreted by cancer cells

Induction of suppressor T cells Blocking antibodies that bind TAAs

Classification of Cancer

Anatomic Site ClassificationIdentified by

tissue originanatomic sitebehaviour of the tumour

Classification of Cancer

Anatomic Site ClassificationCarcinomas originate from

embryonal ectoderm and endodermSarcomas originate from embryonic

mesodermLymphomas and leukaemias

originate from hepatopoietic system

Classification of Cancer

Histologic Analysis ClassificationAppearance of cells and degree of

differentiation are evaluatedGrade 1: Cells differ slightly from

normal cells and are well differentiated

Grade 2: Cells more abnormal and moderately differentiated

Classification of Cancer

Grade 3: Cells very abnormal and poorly differentiated

Grade 4: Cells immature and primitive and undifferentiated; cell of origin difficult to determine

Classification of Cancer

Clinical Staging 0: cancer in situ 1: tumor limited to tissue of origin 2: limited local spread 3: extensive local and regional spread 4: metastasis

Classification of Cancer

TNM ClassificationTumor sizeSpread to lymph nodesMetastasis

TNM Classification System

T (tumour)

Tx Tumour unable to be adequately assessed

T0 No evidence of primary tumour

Tis Carcinoma in situ

T1-4 Progressive increase in tumour size or involvement

TNM Classification System

N (nodes)

Nx Regional lymph nodes cannot be assessed

N0 No evidence of regional node metastasis

N1-3 Increasing involvement of regional lymph nodes

TNM Classification System

M (metastasis)

Mx Not assessed

M0 No distant metastasis

M1 Distant metastasis present, specify sites

Prevention and Detection of Cancer

Reduce or avoid exposure to known or suspected carcinogens

Eat balanced diet Exercise regularly Adequate rest Health examination on a regular basis

Prevention and Detection of Cancer

Eliminate, reduce, or change perceptions of stressors and enhance ability to cope

Enjoy consistent periods of relaxation and leisure

Know 7 warning signs of cancer Self-examination Seek medical care if cancer is suspected

Early Warning Signs of Cancer

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 mole or wart Nagging cough or hoarseness