Singapore — About 90 breast cancer patients may have received “unnecessary treatment” after a test that is used to guide breast cancer treatment produced inaccurate positive test results, according to Khoo Teck Puat Hospital (KTPH) on Friday (Dec 11).

The error that caused the mix-up is believed to be an incorrect staining process for the human epidermal growth factor receptor 2 (HER2) test, according to the hospital’s preliminary investigations.

HER2 testing is performed in breast cancer patients to assess prognosis and to determine how aggressive the cancer is likely to be. It also helps guide medical practitioners on whether the tumours require certain treatments.

Tests are usually performed on breast biopsy samples that are stained with a coloured dye containing antibodies to measure the amount of HER2 protein present in the sample.

HER2 testing is typically used to determine suitability for trastuzumab therapy, which is restricted to HER2-positive individuals as it is expensive and has been associated with cardiac toxicity. For HER2-negative tumours, the risks of trastuzumab clearly outweigh the benefits.

Based on the hospital’s initial estimates, about 180 breast cancer patients may have been inaccurately classified as HER2 positive when they were HER2 negative. About half of these patients may have received unnecessary treatment for HER2 and it confirmed that the treatment they received is likely to be trastuzumab therapy.

The side-effects of trastuzumab therapy may include heart problems, diarrhoea, chills and fever.

The hospital has identified all the affected patients and has stopped HER2 testing in its in-house laboratory since the issue with the test came to light. It has also sent the patients’ samples, dating back to 2012, to external laboratories for expedited retesting and has been contacting patients and their oncologists to offer support as the results trickle in.

While it is unclear exactly when the issue was discovered, the hospital said it reported the incident to the National Healthcare Group (NHG) on Nov 22 and to the Ministry of Health (MOH) on Nov 24.

The NHG has called an independent review committee on how the incident occurred and recommend improvements to the process to prevent similar incidents from taking place.

KTPH CEO Chew Kwee Tiang has apologised to the affected individuals and 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: “We treat this incident very seriously and will take all the necessary steps to ensure this does not happen again.” 

In its press release, the MOH said that it takes a serious view of the incident and has asked the hospital to review its other laboratory protocols as a safety measure. It said KTPH is expected to abide by regulations for private hospitals and medical clinics and added: “Appropriate enforcement action will be taken if a breach of protocol is found.” /TSIG