Biomedical Engineering Reference
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clinically characterised as more aggressive and less responsive to standard
treatment and associated with poorer overall patient prognosis [22]. It should
be possible to differentiate between these subtypes of breast cancers with the
help of spectroscopy, as they have different prognostic implications.
For most cancers, the stage of cancer, or the extent of disease process, car-
ries prognostic implications, where spectroscopy can also play a role as dis-
cussed in the following section.
Determination of Extent of Disease Process
The stage of a cancer is a description (usually numbers I to IV depending on
degree of progression) of the extent to which the cancer has spread. The stage
often takes into account the size of a tumour (T), how deeply it has penetrated,
whether it has invaded adjacent organs, the number of lymph nodes to which
it has metastasized (N, if any), and whether it has spread to distant organs
(M). Staging of cancer is depicted as TNM and is the most important predic-
tor of survival, and cancer treatment is primarily determined by staging.
Cancer staging can be divided into a clinical stage and a pathologic
stage. In the TNM (tumour, node, and metastasis) system, clinical stage
and pathologic stage are denoted by a lowercase “c” or “p” before the stage
(e.g., cT3N1M0 or pT2N0).
Clinical stage is based on all of the available information obtained before
surgery to remove the tumour. Thus, it may include information about the
tumour obtained by physical examination, radiologic examination (x-rays, CT
scans, MRI scans, PET-CT scans, etc.), and endoscopy. Pathologic stage adds
additional information gained by examination of the tumour microscopically
by a pathologist.
Because they use different criteria, the clinical stage and pathologic stage often
differ. Pathologic staging is usually considered the “better” stage because it
allows direct examination of the tumour and its spread, contrasted with clinical
staging, which is limited by the fact that the information is obtained by making
indirect observations of a tumour that is still in the body. However, clinical stag-
ing and pathologic staging should complement each other. Not every tumour is
treated surgically; therefore, pathologic staging is not always available.
Spectroscopy can be of immense value in providing additional informa-
tion to help with staging, in addition to radiological imaging, particularly
in cases where obtaining tissue biopsy is difficult, as the management is
different depending on the stage. Possible examples in which spectroscopy
could help include determination of mediastinal lymph node involvement in
cases of lung cancers, and differentiation of nonspecific lung nodules, liver
lesions, brain lesions, and pelvic masses, to determine if these are benign or
malignant (primary or metastatic) to help guide management.
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