It is an impressive statistic that pathology is used to diagnose 100% of cancers, but this is not the end of pathology’s involvement in helping people with cancer.

October is Breast Cancer Awareness month, so we decided to look at the various ways in which pathology is integral to the effective treatment of breast cancer.

Kathy Wells, Head of Policy, Research and Advocacy at Breast Cancer Network Australia (BCNA) said “Breast cancer is no longer considered to be one disease. There are many different subtypes and the pathology report provides important information to help clinicians and their patients decide the best treatment for each woman’s particular type of breast cancer.”

Pathology’s role in diagnosis

Investigations for breast cancer may begin with an abnormality detected in a mammogram or following a patient noticing an unfamiliar lump in their breast, but a confirmed diagnosis of breast cancer can only be given by pathology testing.

Not all lumps are malignant therefore a tissue sample must be tested. A sample or biopsy of the lump is taken and then examined by a pathologist who will confirm if the lump is cancerous or establish that it is benign.

Pathology provides vital answers

A person with confirmed breast cancer will undergo surgery to have the tumour removed and the tissue is given to a pathologist to examine.

From this surgical sample, the pathologist extracts important information about the tumour type and size. The pathologist will also look at the amount of uninvolved healthy breast tissue which separates the tumour from the ‘margins of excision’ – the edges of the tissue the surgeon has removed. This is important as a measure of complete tumour removal.

The pathologist will examine the same sample to determine a number of possibilities; whether the tumour has spread to adjacent body tissues, if the tumour cells are responsive to the hormones oestrogen and progesterone, and if they express the hallmarks of the HER2 gene or the characteristics of tumours which may be inherited within families.

This forms the advanced information needed by the cancer specialist to determine exactly which treatments should be offered to that person; this is now known as personalised medicine.

How pathology informs treatment

People with breast cancer may need to undergo chemotherapy to treat cancer cells left in the body after surgery and help prevent cancer coming back.

Several different drugs are available to treat cancer, and which drug is most appropriate will depend on the characteristics of cancer, such as what stage it is at and whether it is HER2 positive or negative.

Drugs that are listed on the Pharmaceutical Benefits Scheme (PBS) for the treatment of breast cancer can be subsidised, but only for patients who meet the eligibility criteria. A pathology report is a vital part of demonstrating a patient’s eligibility for access to these drugs.

Trastuzumab works by blocking signals to certain receptors on the surface of cancer cells. The receptors being targeted are made by the HER2 gene and so are called HER2 receptors. When cancer has an ‘overexpression’ of HER2 meaning too many copies of the HER2 gene, more receptors are produced causing cancer to grow quickly. This is called HER2 positive breast cancer.

The drug works on HER2 receptors, it is most effective for patients whose cancer is HER2 positive and is unlikely to be effective for HER2 negative breast cancer. That is why pathology is essential to determine whether or not the drug is right for a patient, and to help them gain access to it.

Monitoring during treatment

Alongside personalising treatment by using genetic information, pathology is also used to help doctors fine-tune chemotherapy. Blood tests will help doctors to monitor neutrophils – a type of white blood cell. As chemotherapy works by “knocking out” the immune system, monitoring white blood cell levels helps doctors understand how a patient is responding to treatment. They can then adjust the dosage and frequency of chemotherapy to ensure the best outcomes for patients.