Cancer




 CANCER 

Cancer  is  one  of  the most  dreaded diseases of  human  beings  and  is  a  major cause  of  death  all over  the  globe. More  than a million   Indians  suffer from cancer  and  a large   number  of  them  die  from  it  annually . The mechanisms  that underlie development of  cancer or oncogenic  transformation  of cells, its  treatment  and control have  been some  of  the most intense areas of  research  in biology  and  medicine. 

  In  our  body, cell  growth  and  differentiation   is  highly  controlled  and  regulated.  In  cancer  cells, there is breakdown  of  these  regulatory  mechanisms. Normally  cells  show  a  property  called  contact  Inhibition by virtue  of  which  contact  with  other  cells inhibits  their uncontrolled  growth. Cancer  cells  appear  to have  lost  this property.  As a  result   of  this, cancerous  cells   just  continue   to  divide  giving  rise  to masses   of cells called  tumors. 

What is Caner ? 

Cancer is an abnormal and uncontrolled   division of cells, known as cancer cells, that invade and destroy  the surrounding tissues. Generally  Cancer is defined as uncontrolled proliferation of cells without any differentiation. Cancer cells are different  from normal cells in some aspects . They do not remain confined to one part of the body. They penetrate and infiltrate into the adjoining tissue and dislocate their functions. Some of the cancer cells get detached  from the main site of origin and travel by blood and lymph to sites distant from the original tumor and form fresh colonies, called metastasis or secondary  growth.

How Cancer Differ from Normal Cells?

Normal cells have limited  life span .They are usually replaced by new cells through cell division  and cell differentiation.Their production is regulated in such a manner that the number of a given cell type remains nearly constant. Normal cells show a property called contract inhibition. Due to this property they contract with other cells, inhibitb their uncontrolled growth. Cancer cells seem to have lost this property. But cancer  cells  do not respond to normal growth control mechanism. These cells proliferate in an unregulated manner and form clones of cells which can expand irregularly. This uncontrolled growth is called tumour or neoplasm. 

Tumors  are of  two  types 

Types of  Tumours :

There are two types of Tumours: benign and malignant. 

(i) Benign Tumour ( = Nonmalignant Tumour): It remains confined to the site of its origin and does not spread to other parts of the body.It causes limited damage  to be body. It is non_ cancerous. 

(ii) Malignant Tumour ( = Cancerous Tumour) : It first grows slowly. No symptoms are noticed. This stage is called the latent stage. The tumor later grows quickly. The cancer cells go beyond adjacent tissue and enter the blood and lymph. Once this happens, they migrate to many other sites in the body where the cancer cells continue to divide. A phenomenon  in which cancer cells spread to distant sites through body fluids to develop secondary  tumour is called metastasis. Only malignant tumours are properly designated as cancer. 

Properties of Cancer Cells:

(i) Uncontrolled proliferative ability. 

(ii) Extracellular growth factors are not required. 

(iii) Overgrowth and ability  to invade new sites ( metastasis).

(iv) Nucleus becomes irregular with abundant granules. 

(v) There is increase in number of lysosomes, reduction in mitochondrial cristae, more melanin and debris in cytoplasm. 

(vi) Cancer cells resist induction of cell death promotes development of tumours.


Types of Cancers :

Four types of cancers are classified on the basis of the tissue where they arose.

1): Carcinomas : Mainly derived  from epithelial cells; include cancers of cervical ( cervix is part of uterus), breast, skin brain, lung, stomach, etc.About 80% of all tumours are carcinomas. 


2): Melanomas : Cancerous growth of melanocytes  ( pigment cells of skin cells) is called melanomas. 


3): Sarcomas : Located in connective tissues. Thus, they include the cancers of bones, cartilage, tendons, adipose tissue and lymphoid tissue. Cancer of bones is called osteoma .Cancers of adipose tissue are known as lipomas.

4): Leukemias and Lymphomas : These are cancers  of haematopoietic cell.Leukemias ( = leukaemias) are characterised by abnormal increase of white blood corpuscles count due to their increased formation in the bone narrow. Leukemias are commonly  called blood cancers.Cancers of lymphatic tissue are termed as lymphomas. Hodgkin's disease is an example of human lymphoma.  In  Hodgkin's disease there is chronic enlargement of the production  of lymphocytes by lymph nodes and spleen.


● Adenoma __ Cancer of glands.

● Myoma__ Cancer of muscular  tissue. 

● Glioma__ Cancer of glial  cells of central nervous system. 

● The most common  cancers in India are mouth_ throat cancer in men and uterine _ cervical cancer in women.



Causes of  Cancer 


 Chemical  and physical  agents that can  cause cancer are called carcinogens, which belong to three categories. 
 
(i) Oncogenic  Transformations : They are agents or factors which bring about changes in genetic formation, e.g., some growth factors, hormones. 

(ii) Tumour Promoters: They promote proliferation of cells which have undergone oncogenic transformation, e.g.,growth factors, hormones. 


(iii) Tumour Viruses : Some Viruses  are known to be connected with oncogenic transformations. 


Carcinogens are as follows: 

1. Physical  Irritants: 

(i) Use of Kangri ( an earthen pot containing  burning  coal) by Kasmiris causes abdominal  skin cancer as  these people keep Kangri close to their abdomen during winter. 


(ii) Betal and tobacco chewing causes oral cancer.

(iii) Heavy smoking  causes lung cancer  and may also cause cancer of oral cavity, pharynx ( throat) and larynx. 

(iv) Japped teeth may cause tongue  cancer. 

(v) Excessive  exposure  to sun light can cause skin cancer. 


2. Chemical  Agents:

Several chemicals are known to cause cancer .These are caffeine, nicotine, products of combustion of coal and oil and  pesticides; constant use of artificial sweetener can cause cancer. An animal protein__ rich diet is known to cause cancer of larger intestine. Breast cancer has hormonal relationship. Thus, some sex hormones and steroids secreted or given in large amounts  may cause  cancer.  Chemical  sweepers can develop cancer of scrotum. Dye workers have a high rate of bladder  cancer.






3. Radiations:

The X_ rays, cosmic rays, ultra__ violet rays, etc.can cause cancer. Japanese  people exposed to radiations from World War II nuclear bombing show five times the incidence of leukemia seen in the rest of the population. 

4. Biological Agents:

Some  viruses  and other parasites, excessive secretion of certain hormones are believed to cause cancers.

Cancer and Genes : 

Cancer _ associated  genes  are divided  into the following  three categories. 

(i) Cancer causing viruses  are called oncogenic  viruses. The genes of oncogenic viruses  are known as viral oncogenes. It is now held that all cells carry some cancer causing  genes called oncogenes which when activated under certain  conditions could change  into oncogenic cells. Jumping genes are often involved  in this conversion. 


(ii) Tumour suppressor genes that inhibit  cell proliferation. 

(iii) Genes that regulate  programmed cell growth.

How Cancer Spreads :

Abnormal  increase in number of cells in a tissue  or organ forms a clone of proliferative cells. This excessive proliferation gives rise to a mass of cells which is initially known as benign tumour. The benign tumour cells enter into the blood vessels and migrate to other sites in the body where these cells continue to divide, such tumour cells are known as malignant  cells and tumours are called malignant tumours. The malignant tumours are designated as cancer.


Detection and Diagnosis  of Cancer:

It depends upon histological features of malignant structure. 

(i) Bone marrow biopsy and abnormal count of WBCs in leukemia. 

(ii) Biopsy of tissue, direct or through endoscopy. Also endoscopic observation. Pap test  (cytological staining) is used for detecting cancer  of cervix and other parts of genital  tract.

(iii) Techniques such as radiotherapy ( use of X_ rays), CT Scan ( computed tomography) MRI Scran ( magnetic  imaging) are very useful  to detect cancers of the internal organs.  In CT Scan X_ rays are used to generate  a three dimensional image of internal organs. In MRI strong  magnetic fields and non_ ionizing  radiations are used to detect pathological and physiological changes in the living tissue. Antibiotics against cancer specific  antigens are also used for detection of certain cancers. Techniques of molecular biology  can be applied  to detect genes in individuals.  Mammography is radiographic examination of breasts  for possible cancer. 



(iv) Monoclonal antibodies coupled to appropriate radioisotopes can detect cancer specific  antigens and hence cancer. 




Different Sites of  Cancer:

Some of the important  sites of cancer are skin, mouth, oesophagus, stomach, colon, rectum, liver, gall bladder ,pancreas, blood lymph, adipose tissue, lung, uterine cervix, breast, brain, penis, prostate, muscles, thyroid, kidney  and bones.


Possible Symptoms of Cancer :

(i) A persistent cough or hoarseness in a smoker. 

(ii) A peristent  change  in digestive and bowel habits. 

(iii) A change in a wart or mole, 

(iv)  A lump or hard area in the breast .

(v) Unexpected diminished or lost appetite. 

(vi) Unexplained  low_ grade fever. 

(vii)  Unexplained  loss  of weight. 

(viii) Any uncurable ulcer.

(ix) Bleeding in vagina at times other than the menstruation. 

(x) Non_ injury bleeding  from the surface  of the skin, mouth or any other opening of the body.


Treatment:

Four general methods of treatment for cancer are currently available. 

1): Surgery: It involves the removal  of the entire cancerous tissue.

2): Radiation therapy: It involves the exposure of the cancerous parts of the body of X_ rays which destroy rapidly  growing  cells without harming the surrounding tissue. 

3): Chemotherapy: It involves the administration of certain anticancer drugs. These drugs check cell division by inhabiting DNA synthesis. These drugs may be more toxic to cancerous cells than to normal cells. Thus chemotherapeutic drugs kill cancerous cells. Majority  of drugs have side effects like hair loss, anaemia etc. Most cancers are treated by combination of surgery, radiotherapy and chemotherapy. Patients are given substances called biological response modifiers like a interferon which activate their immunity system are help in destroying the tumours.

4): Immunotherapy: It involves  natural anti__ cancer immunological defence mechanisms. Monoclonal antibodies are used in various ways, e.g., radioimmunotherapy for treatment of cancer.
 
  These therapies can be used either  singly, or in a suitable  combination. 

Efforts are being made to develop  cancer vaccines. 


TREATMENT 

  Treatment   facilities  should  be available  to  all  cancer   patients. Certain   forms   of  cancer   are  amenable   to  surgical    removal,  while   some  others   respond  favorably  to radiation  or  chemotherapy  or  both. Since  most   of   the   known   methods   of   treatment   have  complementary  effect   on  the  ultimate   outcome  of the  patient,  multi _ modality  approach  to  cancer  control   has  become  a  standard  practice  in  cancer  centres   all  over  the  world.   In   the  developed   countries   today, cancer   treatment  is  geared  to  high  technology.  For   those    who  are  beyond   the  curable  stage,  the   goal  must    be    to   provide  pain  relief.  A largely  neglected  problem in   cancer   care  is  the  management   of   pain.  The  WHO  has   developed    guidelines  on  relief   of   cancer   pain. "  Freedom   from  cancer  pain"  is  now   considered   a  right    for   cancer   patients. 





Theories of Carcinogenesis 

Some of these are being summarised as under :

(i) Mutation Theory  of Carcinogenes : Jacobson (1958 has suggested that mutations may cause  genetic   disorders in a normal somatic cells. 

(ii) Selective gene__ activation theory : According  to this theory certain harmful  but unexpressed protooncogenes become active to oncogenes which cause the loss of the control over growth  and division leading  to the development  of cancerous tumour. Genetic basis of cancer  was explained by Michael Bishop and Harold Varmus (Noble Prize 1989).


(iii) Virus Theory of Carcinogensis : Murphey  and Rous discovered  the possibility of viruses being carcinogenic

Cancer patterns  

 There  are   wide  variations  in  the  distribution   of  cancer  throughout   the world. The  international  variations  in  the  pattern  of  cancer are attributed   to  multiple   factors   such  as  environmental  factors , food  habits , lifestyle,  genetic  factors   or  even  inadequacy   in  detection   and  reporting  of  cases. 

 Hospital   data  clearly   indicates   that  the  two  organ  sites  most  commonly   involved  are : 

(i) The  uterine  cervix  in   women,  and 

(ii)  The oropharynx   in  both  sexes. These  two  sites  represent   approximately   50  per cent of  all  cancer  cases.  Both  these cancers   are predominantly   environment  related   and  have  a  strong  socio__ cultural   relationship.  

Causes  of cancer 

As  with  other  chronic  diseases , cancer  has  a  multifactorial   aetiology. 


1. ENVIRONMENTAL  FACTORS 
  
 Environmental  factors   are  generally    held  responsible   for  80  to  90  per cent  of all  human cancers.  The  major  environmental   factors  identified   so  far  include  : 

(a) TOBACCO  :  Tobacco  in  various   forms  of  its  usage  ( e.g., smoking, chewing )  is  the  major  environmental   cause  of  cancers  of  the  lung,  larynx,   mouth,  pharynx,  oesophagus , bladder,   pancreas   and probably   kidney. It  has  been  estimated  that,  in  the  world  as   a  whole, cigarette   smoking  is  now  responsible   for  more  than  one  million  premature  deaths   each  year.  


(b) ALCOHOL  : Excessive   intake  of  alcoholic  beverages   is  associated   with  oesophageal   and  liver  cancer.  Some  recent  studies  have  suggested   that  beer   consumption   may  be  associated   with  rectal   cancer.  It  is  estimated   that  alcohol  contributed   to  about  3  per  cent  of  all cancer   deaths. 

(c) DIETARY   FACTORS  : Dietary   factors  are  also  related  to cancer. Smoked  fish is related  to stomach cancer,  dietary   fibre to  intestinal   cancer,  beef  consumption   to  bowel  cancer  and  a  high  fat  diet  to  breast  cancer. A  variety   of  other  dietary   factors  such  as  food  additives   and  contaminants  have  fallen  under  suspicion  as  causative   agents. 


(d) OCCUPATIONAL  EXPOSURES: These  include  exposure   to  benzene,  arsenic,  cadmium,  chromium,  vinyl  chloride,   asbestos,   polycyclic   hydrocarbons,  etc. Many  others  remain  to   be  identified.  The  risk of  occupational   exposure   is  considerably increased   if  the  individual  also smoke cigarettes.  Occupational  exposures  are usually   reported  to  account   for  1 to  5  per  cent  of  all  human  cancers.

(e)  VIRUSES:  An intensive  search  for  a  viral   origin   of  human  cancers  revealed   that  hepatitis   B and  C  virus  is  causally   related  to  hepatocellular   carcinoma.  The relative  of  Kaposi's  sarcoma occurring  in  patients   with  HIV  infection   is  so  high  that  it  was  the  first  manifestation   of  the  AIDS epidemic   to  be  recognized  . Human papilloma virus   ( HPV) is  a  chief  suspect   in  cancer  cervix.


(f) PARASITES: Parasitic  infections  may  also  increase   the  risk  of  cancer, as  for example,   schistosomiasis  in Middle  East  producing  carcinoma   of  the  bladder  


(g) CUSTOMS, HABITS AND LIFESTYLE: To the  above  causes  must  be  added  customs,  habits  and  lifestyles  of  people   which  may  be  associated   with  an  increased  risk  for  certain  cancers . The   familiar examples  are the demonstrated    associated  between   smoking  and  lung  cancer, tobacco   and  betel  chewing   and  oral cancer,  etc. 


(h)  OTHERS :  There  are  numerous   other  environmental  factors  such as  sunlight,  radiation, air  and  water  pollution,  medications  (e.g.,  oestrogen)  and   pesticides   which  are  related   to  cancer. 


2. GENETIC FACTORS  
   
    Genetic  influences  have   long  been  suspected. For  example,  retinoblastoma   occurs  in  children   of  the  same  parent. Mongols  are  more  likely   to  develop  cancer  ( leukaemia)  than  normal  children.  There  is  probably   a  complex  interrelationship   between   hereditary   susceptibility   and   environmental   carcinogenic   stimuli  in   the  causation   of  a  number   of  cancers. 

Cancer  Control:

Cancer  control  consists   of  a  series   of  measures   based  on  present   medical  knowledge   in  the  fields  of  prevention,  detection , diagnosis,  treatment , after  care  and  rehabilitation,  aimed  at  reducing  significantly    the  number  of  new  cases, increasing   the  number  of  new  cases, increasing   the  number  of  cures  and reducing   the  invalidism  due  to cancer. 

  The  basic  approach   to  the  control   of  cancer  is  through   primary   and  secondary  prevention.  It  is estimated   that   at  least one_  third   of  all  cancers  are preventable. 

1. PRIMARY  PREVENTION 
 
 Cancer prevention   until  recently   was  mainly  concerned   with  the  early  diagnosis   of  the  disease  ( secondary   prevention ), preferably   at  a  pre_  cancerous   stage. Advancing    knowledge  has increased   our  understanding   of  causative   factors  of  some  cancers   and  it  is  now  possible   to  control  these  factors  in  the  general   population   as   well  as in   particular   occupational  groups. They  include  the  following: 


(a)  CONTROL  OF  TOBACCO AND ALCOHOL    CONSUMPTION:   Primary prevention offers the  greatest  hope for  reducing   the number of tobacco _ induced  and alcohol  related  cancer deaths. It has  been estimated that control  of  tobacco  smoking alone  would  reduce  the  total  burden  of  cancer  by over  a million   cancers   each  year. 


(b) PERSONAL HYGIENE :Improvements in personal  hygiene may  lead  to declines  in  the  incidence  of  certain types   of  cancer, e.g., cancer  cervix. 

(c)  RADIATION : Special   efforts  should  be made to reduce  the  amount  of  radiation  ( including  medical  radiation) received  by  each  individual   to a minimum   without  reducing   the benefits .


(d)   OCCUPATIONAL   EXPOSURES : The  occupational  aspects  of  cancer   are  frequently  neglected.  Measures to protect workers   from  exposure to  industries. 


(e) IMMUNIZATION  : In the  case  of  primary  liver  cancer, immunization   against   hepatitis  _ B virus  presents  an  exciting   prospect.


(f) FOODS,   DRUGS  AND  COSMETICS: These should  be tested  for  carcinogens. 

(g) AIR   POLLUTION  : Control of  air  pollution  is  another  preventive measure  undertaken.

(h) TREATMENT  OF  PRECANCEROUS  LESIONS  : Early  detection  and prompt  treatment  of precancerous  lesions such  as cervical tears, intestinal   polyposis, warts, chronic  gastritis, chronic cervicitis,  and   adenomata  is  one  of   the   cornerstones  of  cancer  prevention.  

(i)  LEGISLATION  : Legislation has  also a  role  in  primary  prevention. For  example, legislation  to control known  environmental  carcinogens  (e.g., tobacco,  alcohol,  air pollution) is  inadequate  or  only  moderately  enforced  in  a number  of countries.


(j) CANCER  EDUCATION  : An  important  area of  primary  prevention   is   cancer  education.  It should  be directed  at " high_ risk"  groups. The aim  of cancer  education  is to motivate  people to seek early  diagnosis  and early  treatment.  Cancer  Organization  in many countries  remind  the  public of  the early  warming  signs   " danger  signals")  of cancer. 

These are  : 

a.  a lump  or  hard  area in  the  breast 

b.   a  change  in  a  wart  or  mole 

c.  a   persistent  change in  digestive  and           bowel habits.

d.  a  persistent  cough  or  hoarseness 

e.  Excessive  loss of  blood  at  the monthly 
      period  or  loss  of  blood outside  the           usual dates 

f.   blood  loss  from  any  natural  orifice

g. a  swelling  or  sore  that  does  not  get            better

h.  Unexplained  loss of  weight. 


   There  is  no  doubt  that  the  possibility   for   primary   prevention   are many. Since  primary   prevention  is  directed   at  large  population  groups   (e.g., high  risk  groups,  school   children,  occupational  groups, youth  clubs),  the  cost  can be high  and programmes  difficult  to  conduct. Primary  prevention, although  a hopeful  approach , is still in its   early  stages. Major risk  factors  have  been identified  for  a small number  of cancers  only and  far more research  is  needed  in  that  direction. 



2.  SECONDARY PREVENTION 
 
  Secondary  prevention   comprise   the   following   measures  :


(i)  CANCER  REGISTRATION:

  Cancer   registration  is  a   since   qua  non  for  any  cancer  control  programme. It  provides   base   for   assessing   the  magnitude   of  the  problem   and  for  planning   the   necessary   services.  Cancer  registries   are  basically   of  two  types : hospital _ based  and  population   based. 

(a) HOSPITAL  _ BASED  REGISTRIES : The  hospital _  based  registry   includes  all  patients  treated   by  a particular  institution,  whether   in_patient  or  out_  patients.  Registries  should   collect  the  uniform  minimum  set  of  data  recommended  in  the  " WHO Handbook  for  Standardized  Cancer  Registers". If  there  is   a  long  _ term  follow _ up  of  patients ,  hospital _ based  registries  can  be  of  considerable   value  in  the  evaluation  of  diagnostic  and  treatment  programmes.  Since  hospital  population   will  always   be  a  selected  population,  the  use  of   these  registries   for  epidemiological   purposes is  thus  limited. 

(b) POPULATION _ BASED  REGISTRIES :A right  step   is  to  set  up  a  "  hospital  _ based  cancer   registry "  and extend  the same  to a " population _ based  cancer  registry". The aim  is  to  cover  the  complete   cancer  situation  in a  given  geographic   area . The  optimum  size  of  base  population   for  a population  based  cancer registry   is  in   the range    of   2__ 7 million.  The  data  from  such  registries  alone  can   provide   the  incidence   rate   of  cancer   and  serve   as   a  useful   tool   for  initiating   epidemiological   enquiries   into   causes    of  cancer,  surveillance   of  time  trends,  and  planning   and  evaluation   of  operational   activities  in  all  main  areas   of  cancer   control. 


    In  India  population  _  based   cancer    registries      have   been   established   at  Bangalore,  Mumbai,  Delju,  Bhopal,  Barshi   and  Chennai   under   the  National  Cancer  Registry    Project   of   the  ICMR. 

(ii)  EARLY  DETECTION   OF CASES 
 
        Cancer    screening   is   the  main  weapon  for  early  detection     of  cancer  at  a  pre_ invasive  ( in  situ) or  pre_ malignant  stage.  Effective   screening  programmes   have    been   developed    for  cervical   cancer ,   breast   cancer      and   oral  cancer .Like   primar  prevention, early   diagnosis  has    to    be  conducted   on  a   large   scale  ; however,  it  may   be  possible  to   increase the   efficiency   of  screening programmes  by focusing   on  high _  risk  groups . Clearly,  there  is   no  point  in   detecting   cancer  at  an  early  stage   unless  facilities   for  treatment  and  aftercare  are available . Early  detection  programmes will  require  mobilization   of  all   available  resources  and  development   of  a  cancer   infrastructure   starting   at  the  level  of  primary  health   care,  ending  with  complex  cancer  centres  or  institutions  at  the   state  or  national  levels. 



NATIONAL CANCER  CONTROL  PROGRAMME 

  Cancer   is   an   important   public   health  problem   in   India,   with  nealy    7_ 9  lake  new     cases  occurring    every  year  in   the   country . It  is   estimated   that   there   are   2 _ 2.5  million   cases  of   cancer   in   the  country  at  any  given  point   of   time.  With  the  objectives  of   prevention,  early  diagnosis   and  treatment,  the  national   cancer   control   programme  was   launched   in    1975 _ 76.  In  view   of   the  magnitude  of   the   problem   and   gaps   in   the   availability   of  cancer    treatment   facilities   across   the   country,  the   programme   was   revised   in   1984_  85  and   subsequently   in  December   2004.  In   the    year     2011,   this   Programme   was  integrated  with    National  Programme   for   Prevention   and    control   of   Cnacer,   Diabetes  , Cardiovascular  Disease   and  Stroke. The  objectives   of   the  programme  are : 

a.  Primary   prevention   of  cancers     by           health    education  ;

b.  Secondary   prevention  i.e,  early                     detection  and    diagnosis   of  common          cancer    such    as   cancer      of   cervix,           mouth ,  breast  and  tobacco   related             cancer  by  screening / self  examination           method:  and 

c.     Tertiary    prevention i.e., streng__                     thening  of   the   existing   institutions          of  comprehensive  therapy   including            palliative  care. 




















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