Can Tumour Markers Screen for Cancer? Biopsy and Staging

Tumour markers should not be used to screen for cancer. They are not specific, they can rise in conditions that are not cancer, and a raised marker never establishes the diagnosis. Their place is in monitoring patients already known to have cancer. The diagnosis itself is made by biopsy, and treatment begins only after the disease has been staged.

That sequence, from suspicion to a staged diagnosis, is how Dr. Mohit Agarwal, Principal Director & Head Medical Oncology, Fortis Hospital, Shalimar Bagh, New Delhi, India, sets out how the first doctor in a patient's journey should think. The sequence guards against three shortcuts: reassurance from normal blood tests, a raised marker treated as proof, and treatment started before anyone knows what stage the disease is. This article sets out each step. The warning signs that should trigger the process are covered in the series pillar, Diagnosis and Detection of Cancer: A Complete Guide.

Can tumour markers be used for cancer screening?

No. Asked during the session whether tumour markers could be added to a general health check-up as a screening test, Dr. Agarwal was clear. Tumour markers are substances, usually proteins, measured in the blood that can be produced by some cancers. Because they are not specific to cancer, they can be raised in non-cancerous conditions as well. A screening test that flags healthy people with benign conditions creates anxiety and unnecessary investigation without reliably finding early cancer.

Where tumour markers do earn their place is after diagnosis. In a patient known to have cancer, a marker can be used to monitor the disease, tracking the response to treatment and signalling a possible recurrence.

CA-125 and ovarian cancer

A doctor in the session pressed the point for ovarian cancer: if a patient has a very small ovarian cancer, can a tumour marker help make the diagnosis? Dr. Agarwal's answer was that a tumour marker is a red flag in a patient already suspected of having the disease. A doctor who sees a raised marker and thinks of ovarian cancer is moving in the right direction, but the marker does not clinch the diagnosis.

He extended the example deliberately. Take a patient with an ovarian mass, signs of spread and a raised CA-125, the marker most associated with ovarian cancer. Can treatment start directly? His answer was no. The diagnosis must first be confirmed by histopathology, either from a biopsy or from a complete surgical resection, and only then can treatment go ahead.

Normal blood tests do not rule out cancer

A patient with cancer can have completely normal blood tests. Dr. Agarwal lists this among the common myths that patients hold. A normal complete blood count, normal kidney function tests and normal liver function tests do not exclude cancer, because many cancers do not affect them, particularly at an early stage.

The practical rule follows directly. When a warning sign is present, normal routine bloods are not a reason to stop investigating. They describe the patient's general condition; they do not answer the question of whether cancer is there.

Biopsy: how cancer is confirmed

Cancer is diagnosed through a biopsy of the affected tissue. A biopsy removes a small sample, which a pathologist examines under the microscope to establish whether cancer is present and what kind it is. This histopathological diagnosis is the foundation of everything that follows.

Many patients fear a biopsy because they believe that putting a needle into a cancer will make it spread faster. Dr. Agarwal is categorical that this fear is misplaced: spread along the needle track is rare, and the risk is far outweighed by the need for an accurate diagnosis. Modern biopsy is also highly targeted. His example was a CT-guided lung biopsy, in which scan images guide the needle precisely into the centre of the mass. The precision of the technique is part of the answer to the patient's fear. Dr. Agarwal's later masterclass returns to this myth, and to those surrounding staging and surgery, in Does a Biopsy Spread Cancer? Staging and Surgery Myths.

When the presentation is unusual

The same discipline applies to presentations that do not fit a textbook pattern. One doctor described a male patient with a cystic breast mass containing solid components, draining thick, blood-stained, dark fluid, with histology not yet available. Dr. Agarwal's first principle was that any discharge from the breast in a man is abnormal. The differential includes infection, malignancy and a problem arising from the chest wall. The crux is to obtain imaging and a histopathological diagnosis. If it proves to be breast cancer, it needs to be treated without delay. This exchange and the other questions doctors raised are on the Live Discussion page.

Why staging comes before treatment

Once cancer is confirmed, should treatment start immediately? Dr. Agarwal's answer is yes, promptly, but not before two things are known: the stage of the disease, and its nature as defined by the biopsy. Only with both can the right treatment be chosen.

Staging describes how far a cancer has spread. Every cancer is described in four stages. In his framing, stages one to three are local or regional disease that can be cured, and even some patients with stage four disease can be cured completely. The stage decides whether the first step is surgery, medical treatment or a combination, which is why skipping it can commit a patient to the wrong pathway.

Positron emission tomography and computed tomography (PET-CT)

PET-CT is a scan that combines a CT image of the body's structure with a PET image of metabolic activity, which highlights cancer deposits throughout the body in a single examination. In the colorectal pathway he described, Dr. Agarwal uses PET-CT scanning to determine whether a cancer is at stage one, two, three or four. Standard guidelines stage colorectal cancer mainly with contrast-enhanced CT of the chest, abdomen and pelvis, adding pelvic MRI for rectal cancer, and reserve PET-CT for selected cases.

A worked example: the colorectal cancer pathway

Asked about the current management strategy for colorectal cancer, Dr. Agarwal described a sequence that shows how diagnosis and staging drive treatment:

1. Biopsy, to establish what sort of cancer it is.
2. PET-CT scanning, to establish the stage.
3. Stages one to three: the patient may go to surgery, with further treatment decided on the basis of the pathology report.
4. Stage four: medical management comes first.

The cost of the operation is on the colorectal resection surgery cost page.

The order of treatment varies by site. In rectal cancer at stages two and three, chemotherapy and radiotherapy are usually given before surgery to shrink the tumour and lower the risk of local recurrence. The principle Dr. Agarwal sets out holds throughout: the stage and the biopsy decide the plan, not the other way round.

Bringing diagnosis closer to the patient

One doctor in the session asked how cancer diagnosis can be brought to local communities, where specialist services are scarce. Dr. Agarwal's answer was that it comes only through education and awareness: people with any of the seven warning signs should talk to their doctor, undergo screening and seek a consultation early. Doctors who know the sequence of biopsy, staging and treatment avoid the delays that turn curable disease into advanced disease. Screening of healthy people, set out in the pillar, extends the same logic to people with no symptoms at all.

For the referring doctor, the checklist is short. Act on a warning sign even when routine bloods are normal. Do not treat a tumour marker as a diagnosis. Obtain a biopsy, reassure the patient that the risk of it spreading the cancer is very small, and make sure the disease is staged before treatment is chosen. What happens next, from chemotherapy to immunotherapy and the order in which they are used, is covered in Can Chemotherapy and Hormone Therapy Be Given Together?. Other perspectives on the same workup are in How Cancer Is Diagnosed: Tests, Biopsy and Tumour Markers.