Diagnosis of Cancer and Its Methodology

In last issue we described cancer and its warning symptoms, one should be aware of. Now, I will explain how a diagnosis and staging is reached once a cancer is suspected.

For this, let us divide tumors into 2 categories. First, those visible to external examination such as breast cancer and oral cancers; 2^nd those requiring internal inspection such as lung, and intestinal cancers.

Establishing a diagnosis of cancer entails a biopsy (retrieving tissue from area of concern) or fine needle aspiration cytology. There exists a common misconception that biopsy causes early spread of the disease and should be discouraged. However, it must be stated that biopsy provides the mandatory tissue proof for the disease before any treatment can be instituted, and remains a gold standard.

Only a few examples exist where this may not be mandatory such as localized – kidney mass, pancreatic mass, complex ovarian mass or a testicular mass, where in a direct surgery may achieve both therapeutic (removal of localized disease) and diagnostic aims. Also certain tumors which can be defined by highly specific tumor markers (explained later), may also not require tissue diagnosis.

While organs accessible to external examination can be easily targeted for biopsy, the internal ones need special assessment before a biopsy and staging can be done.

These are:

COMPUTED TOMOGRAPHY (CT SCAN)

Multiple Xrays are taken through a part of the body, which are then processed by the computer to form slices of the body in various directions, to give a 3 dimensional estimate of the disease. An investigation of choice to image the lungs (thorax), abdomen and bones. Often used in conjunction with oral and intravenous contrast to opacify the intestines and blood vessels, respectively, to increase sensitivity.

MRI (MAGNETIC RESONANCE IMAGING)

It utilizes external magnetic fields to image the nuclei of the atoms inside the body through the property of nuclear magnetic resonance. It is better than CT to image the brain, spinal cord, soft tissues such as blood vessels and muscles; and complements when used with CT to image pelvis, liver and biliary structures.

FDG- PET SCAN (FLUORODEOXY GLUCOSE, POSITRON EMISSION TOMOGRAPHY)

It is the new method of functional imaging, now commonly used with compulsorily incorporated CT scans for detecting and staging cancer. It utilizes radio-labeled glucose which emits low dose radiation (gamma rays) and is injected into the vein of the patient. This radiation is then picked up by the PET camera and later fused with CT images. It utilizes the concept that rapidly multiplying or active areas will uptake more glucose and hence emit more gamma rays than the background tissue. This will then be easily detected as an abnormal “hot” area on the CT scan. PET CT scan full body in one go. Figure 1 (shows a plain CT scan “A” – with a lung nodule/mass and a PET CT scan “B” confirms it is functionally active “hot”– but only a biopsy will confirm malignancy).

ENDOSCOPY

It is the process of looking inside the body through an endoscope (usually a flexible fibre-optic instrument), which also helps to take guided biopsy from concerned areas. It is utilized to see inside of nose, larynx (voice box), esophagus (food pipe), stomach, small and large intestine, airways and lungs. Nowadays internal ultrasound (USG) can be done through endoscopes by small USG probes fitted on its tip which help do better guided biopsy and staging. Figure: shows a flexible endoscope with a light source to visualize the stomach.

TUMOR MARKERS

These are certain chemicals released in excess by the affected organ, which can be detected and measured in the blood. They can not only assist in suspecting and detecting cancer but, can at times be even confirmatory of it (foregoing the so called mandatory biopsy). Such examples are though few.

PATHOLOGY AND LABS

Once a biopsy is retrieved, it is subjected to methodical pathological testing which is then evaluated under the microscope by an expert onco-pathologist. At times, further complex genetic and molecular processes are done on the tissue to establish the subtype of the cancer, bringing in the role of geneticist and molecular biologist.

All of the above are an essential and integral part of a best cancer doctors and their units which collectively helps reaching a correct diagnosis and staging. After all, only a correct diagnosis can lead to a correct treatment and thence, a correct outcome – which can possibly be a cure.