Approximately 90 breast cancer patients at the Khoo Teck Puat Hospital (KTPH) since 2012 may have received unnecessary treatment due to inaccurate test results.

The inaccurate test results have to do with the Human Epidermal Growth Factor Receptor 2 (HER2), a gene that controls how a healthy cell grows, divides and repairs itself.

Incorrect staining process produced inaccurate results

In a statement on Friday (Dec. 11), KTPH said that it was informed by its laboratory on Nov. 19 that its immunohistochemistry (IHC) HER2 tests were producing higher-than-expected rates of positive results.

A HER2 positive test result suggests that the HER2 gene is malfunctioning, making too many copies of itself, overproducing HER2 proteins and leading to uncontrolled growth of cells.

Preliminary investigations by the laboratory suggested that an incorrect staining process had produced inaccurate HER2 results.

In the IHC HER2 test, the tissue sample from the patient is "stained" with antibodies that have a coloured dye. These antibodies will attach themselves to HER2 proteins. A doctor then reads the slide under a microscope to classify the sample.

The IHC HER2 test is conducted on patients who have breast cancer, in order to to classify the patient’s HER2 status and help guide treatment. It does not diagnose whether the patient has cancer.

KTPH reported the incident to the National Healthcare Group (NHG) on Nov. 22 and to the Ministry of Health (MOH) on Nov. 24.

About 180 patients may be re-classified

Since discovering the issue, KTPH has investigated the extent of the issue and identified all affected patients, whose samples date back to 2012, when KTPH first began doing HER2 testing.

Their samples have all been sent to various external laboratories to expedite re-testing for HER2.

Based on initial estimates, about 180 breast cancer patients may be re-classified from HER2 positive to HER2 negative.

About half — or 90 — of these patients may have received unnecessary treatment for HER2, typically in the form of the drug Herceptin (Trastuzumab).

Common side effects of Herceptin include diarrhoea, chills, and fever. About three to four per cent of people who undergo Herceptin treatment may also experience heart problems.

According to the American Cancer Society, HER2 cancers tend to grow and spread faster than other breast cancers, but are more likely to respond to treatment with drugs that target the HER2 protein.

On the other hand, HER2 negative cancers do not typically respond to treatment with drugs that target HER2.

"Deepest apologies"

As some of the re-test results return, KTPH has begun reaching out to patients and their treating oncologists to offer support. The process of contacting affected patients is ongoing, said the hospital.

The treatment regime of affected patients will be reviewed by their oncologists, said KTPH.

The laboratory has also stopped in-house IHC HER2 testing, to ensure patient safety.

NHG has also convened an independent review committee, which includes external experts, to do a thorough review of how the incident occurred to improve the process and prevent recurrence of similar incidents.

Chew Kwee Tiang, CEO of KTPH, said:

"I would like to convey my deepest apologies to all the affected patients, their families and their treating oncologists. I am very sorry that they have to go through this.

We will provide all the necessary support and assistance, and will do our best to take care of them."

She added that they treat the incident "very seriously" and will take all necessary steps to ensure that it does not happen again.

Patients who have any related queries may reach KTPH at their dedicated hotline at 6602-3333.

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Top image via Facebook / Khoo Teck Puat Hospital.