The Purpose of Blood Tests for People with Cancer

17 Dec 2015 by Krystal Barter
The Purpose of Blood Tests for People with Cancer

Deb, a Pink Hope Community member, is a medical scientist who has worked in the pathology industry for over 15 years. She has kindly written a post explaining blood tests and their use in monitoring breast and ovarian cancer.

I have worked in the pathology industry as a medical scientist for over 15 years, and to this day it still amazes me that as patients when we enter the medical mind field of cancer screening, and diagnosis; we often go through a barrage of test without fully understanding their relevance to how it is used in the diagnosis or monitoring of particular conditions, and the effects of any treatments on our internal system. One blood test that may be needed is monitoring of what is called a tumour marker.

A tumour marker is a protein that is present in our normal tissues at some stage in our development but whose level changes as a cancer grows or shrinks.
In an ideal world the perfect tumour marker would be:

1. Cancer specific (seen only when a particular cancer is present) and
2. Produce levels in the blood that are in proportion to the amount of tumour that is present

However we do not live in an ideal world and we rarely have markers that can be used to diagnose a cancer as they are often not specific enough. Mostly markers are useful to monitor how a cancer is responding to treatment. One example is for women with ovarian cancer. The tumour marker CA125 is commonly used to assess whether women have responded to chemotherapy. The table below has more information about this marker. It shows that this marker can be increased in a number of cancer conditions as well as in benign (non-cancer) conditions.

As the levels for each person can be different, it is very important, to establish that person’s tumour marker level before cancer treatment commences as other tests during or after treatment can be compared against that level.

You can usually expect results the same day, or at least within 24hrs for samples from rural patients.

Tumour Marker Cancer commonly associated with elevated levels Benign conditions associated with elevated levels
Ca 125 ref range: <35   kU/LElevated in about 90% of women with advanced ovarian cancer and correlates with tumour volume and cancer stage Ovarian Cancer (most often)
Endometrial Cancer
Cervical Cancer
Lung Cancer
Breast Cancer
Colo-rectal Cancer
Pancreatic Cancer
Benign ovarian disease
Pelvic inflammatory disease
Ascitic or pleural fluid accumulation
Abdominal injury

Although tumour markers can be helpful, from a patient’s point of view blood tests can often be a traumatic experience. Often people become anxious whilst waiting for the results and some people become very focussed on the result. As these tests can be influenced by other non-cancer related processes in the body, fluctuations in results that are still within in the normal range are common. All blood marker results must be used together with other information eg from imaging and other investigations to work out if/how much a tumour is responding.



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