The staging
of cancer is the classification of the disease in terms of extent, progression
and severity so that generalizations can be made about prognosis & the
choice of therapy. From an operational point of view, staging is 'the procedure
of assigning a simple code designator to a patient in accordance with an
established set of rules' (Mountain et al. 1974). The axis of classification
most useful for predicting outcome & selecting the mode of therapy is the
anatomical extent of disease at the time of diagnosis.
The staging
of cancers by anatomical extent dates from the beginning of the 20th century
when C.F. Steinthal, in 1905, introduced a clinical staging of breast cancer.
Later on in 1940, Paterson developed the refined clinical staging system for
breast cancer known as the Manchester classification and Haagersen & Stout
(1943) developed the Columbia clinical classification.
In 1930,
Cuthbert Dukes introduced a pathological stage classification for rectal
carcinoma based on the local spread of the primary tumour & the regional
lymph node status. It was later on applied to carcinoma of colon also (1945).
The Dukes system was repeatedly modified, leading to considerable confusion (Kyriakos
1985) and is replaced by the current AJCC (American Joint Committee on cancer)/UICC
(Union Internationale Contre le Cancer) TNM classification.
Pioneer work
in staging of gynaecological tumours was done in the 1930’s with the
publication of an atlas illustrating the division of cancer of uterine cervix
into four stages by the League of Nations Health Organization. Since 1958 FIGO
(Federation Internationale de Gynecologie et d' obstetrique) has been engaged in
gynaecological tumour staging. Between 1960 & 1972 a clinical staging system
was developed in collaboration with the UICC and the AJC (American Joint
Committee for cancer staging and End Results Reporting).
The TNM (Tumour
-Node -Metastasis) system introduced beetween 1943 and 1952 by Pierre Denoix at
the Institute Gustav Roussy, Villejuif, France has gradually been forged to
provide an international basis for categorizing cancers and to allow for
comparable end results in reporting. The UICC and AJCC were constituted to
develop a meaningful staging system using TNM categories in the early 1950's.
After considerable dialogue, both groups published systems using the same TNM
language but with stages defined differently. In 1982, at the 13th International
Cancer Congress, an AJCC-UICC Joint meeting agreed to formulate a single TNM
uniform staging system internationally accepted and approved by all national TNM
Committees and by FIGO & SIOP (Societe Internationale d’Oncologie
Pediatrique). The unified inter-nationally stage grouping is comparable with and
translatable into former staging classifications e.g. the Dukes system and its
various modifications, the Australian Clinico-pathological Staging System, or
the Japanese Stage grouping for Colorectal Carcinoma or Robson's Staging system
for renal-cell carcinoma.
The
objectives of a classification system for cancer as defined by UICC are-
1) Aiding
the clinician in planning treatment.
2) Giving
some indications of prognosis.
3) Assisting
in the evaluation of end results.
4)
Facilitating the exchange of information among treatment centres.
5) Assisting
in the continuing investigation of human cancer.
The quality
of staging is vital to achieve the above objectives. Variations in staging
procedures can affect the results in the same population. This refers to the
clinical as well as to pathological classification. The same is true for
different methods of pathological staging. Here, the choice of tissue blocks and
the number of examined lymph nodes can be crucial. There are international
efforts to recommend defined methods for staging, for example the proposals of
the International Documentation System (IDS) for colorectal cancer.
The
important staging systems currently in practice are-
There are
three basic variables
T: The
extent of primary tumour.
N: The
status of regional lymph nodes.
M: The
presence or absence of distant metastases
To these
three components are assigned a series of numbers (T 0, T 1. T 2, T 3 and T 4;
No, N1, N2, and N3; Mo, M1) indicating ascending degrees of anatomical
involvement of a particular malignant tumour. The TNM system is applicable to
most solid tumour sites and entities. Exceptions are lymphomas and leukaemias,
for which the TNM formula is not appropriate. TNM is a dual system that
provides, first, a classification based on observations before starting
treatment and then a classification using additional information that becomes
available from surgery and histo-pathological examination. The TNM system allows
a condensation of the many individual combinations of T, N, and M categories
into a smaller number (usually four) of TNM stage groups which facilitates
tabulation and statistical analysis. At present TNM classification exists for 46
tumour sites and entities.
Each patient
is first classified clinically cTNM based on evidence acquired before treatment
from physical examination, imaging, endoscopy, biopsy, surgical exploration, and
other relevant examinations. The clinical TNM classification is the basis for
selecting the primary treatment and for comparing results of different
treatments. After surgical treatment and adequate histopathological examination
the pTNM classification is made. It is, of course, more reliable than the cTNM
classification and provides more accurate data to estimate prognosis and to
evaluate results of surgical treatment. Moreover, pTNM is, together with the R
classification, relevant for the selection of post- surgical radio- and/or
chemotherapy.
The stage
grouping should be such as to ensure, as far as possible, that each group is
more or less homogenous in respect of prognosis and that the survival rates of
these stage groups for each cancer site are distinctive. Generally there are
four stages I-IV.
FIGO has
defined the most widely accepted staging system for carcinoma of cervix which is
based on careful clinical examination and the results of specific radiological
studies and procedures. These should be performed and the stage should be
assigned before any definitive therapy is administered. The clinical stage
should never be changed on the basis of subsequent findings. In its rules for
clinical staging, FIGO states that palpation, inspection, colposcopy,
endocervical curettage, hysteroscopy, cystoscopy, proctoscopy, intravenous
urography and radiographic examination of the lungs and skeleton may be used for
clinical staging. Suspected bladder or rectal involvement should be confirmed by
biopsy. Examination under anaesthesia is desirable but not required.
The Ann
Arbor classification system with the Cotswolds modifications is used for the
staging of Hodgkin's lymphomas and non-Hodgkin's lymphomas. This system is based
on the fact that lymphoma usually spreads by contiguity to predictable lymph
node sites. Four stages are recognised based on the extent of lymphatic
involvement or the spread to distant extra-lymphatic organs. Lack of systemic
symptoms is specified as A, whereas B indicates presence of unexplained weight
loss greater that 10 %, fevers or night sweats.
The
International Lymphoma Study Group have recently provided a new revised
classification for lymphomas known as REAL classification (Revised
European-American classification of Lymphoid neoplasms). According to this, the
lymphoma categorization is based on currently available morphologic, immunologic
and genetic techniques. The present proposal divides lymphomas according to
their immunophenotypes into B- and T -Cell neoplasms and then further according
to the level of differentiation into precursor and peripheral types.