SickKids study finds blood tests alone may be effective strategy for detecting cancer relapse in certain patients

For most cancer patients, medical tests and examinations don’t end with the completion of therapy, even if their cancer has gone into remission. They will be due for several follow-up appointments, which can include blood tests, imaging tests and other exams as part of a surveillance protocol to detect possible relapse.

One of the regular follow-up blood tests is for the detection of tumour markers. Tumour markers are substances made by cancer cells or normal cells in response to cancer. In some types of cancers, tumour markers will decrease with treatment and are helpful in predicting outcomes, which is why researchers at The Hospital for Sick Children (SickKids) set out to discover if tumour markers could adequately detect cancer relapse independently of imaging tests.

Imaging tests such as CT scans can deliver significant cumulative radiation doses and often require sedation or general anesthesia in children. The research team, led by SickKids Drs. Adriana Fonseca, Research Fellow, Haematology/Oncology, Armando Lorenzo, Staff Physician, Urology and Furqan Shaikh, Staff Physician, Haematology/Oncology, wanted to determine if CT scans could be reduced or eliminated in the surveillance protocol of children with malignant germ cell tumours by using tumour markers instead. Their study was published online in the Journal of Clinical Oncology on Dec. 23, 2018.

Germ cell tumours are a type of tumour that begins in the cells that give rise to sperm or eggs. They can occur almost anywhere in the body and can be either benign or malignant. They’re also called “secreting tumours” because they secrete a substance called alpha-fetoprotein (AFP) and some may also secrete a hormone called human chorionic gonatotropin (hCG), both of which can be used as tumour markers.

“It was ideal to study children with malignant germ cell tumours because we know these kinds of tumours secrete tumour markers that are easy to detect,” says Fonseca, who was the lead author of the study. “Furthermore, although most surveillance protocols call for CT scans of these children, there is no particular scientific evidence that supports this practice. If tumour markers are sufficient in detecting relapse in this population, we could be reducing or eliminating a large number of unnecessary tests.”

The researchers reviewed data from 284 patients with low-risk and intermediate-risk malignant germ cell tumours who were enrolled in a clinical trial with the Children’s Oncology Group that ran from 2003 to 2011. All patients had elevated tumour marker levels at the time of diagnosis. 48 patients (16.9 per cent) experienced a relapse and 47 of the relapses could be detected by tumour marker elevation.

Most patients who had relapsed (64.6 per cent) had both abnormal tumour markers and abnormal imaging results. 33.3 per cent of patients who had relapsed had abnormal tumour markers with normal or unknown imaging. One patient (2.1 per cent) had abnormal imaging with unknown marker levels at relapse.

“These findings suggest that monitoring of tumour markers is a sensitive and effective strategy for detecting relapses in this population of patients,” says Fonseca. “It may be appropriate to use tumour marker monitoring as the main surveillance strategy after therapy for patients with positive tumour markers at diagnosis.”

All patients who relapsed in this trial had elevated tumour markers at initial diagnosis and therefore the results of the study cannot be extrapolated to other patients. The research team hopes to evaluate the value of frequent surveillance imaging in children, adolescents and young adults with malignant germ cell tumours that do secrete tumour markers at diagnosis versus those that do not in a clinical trial.

Evaluating the benefits and risks of surveillance imaging will enable clinicians to make well-informed decisions that reduce the risk of potential harm and add value to care. This work is in line with Choosing Wisely Canada, a campaign to help clinicians and patients engage in conversations about unnecessary tests and treatments. Read more on Choosing Wisely at SickKids.

This study was supported by the Rare Disease Foundation, the St. Baldrick’s Foundation and the SickKids Foundation. It is an example of how SickKids is making Ontario healthier, wealthier and smarter.