BURLINGTON, ONT. -- A new study has found no significant change in the number of new cancer diagnoses in Canadian children during the first nine months of the COVID-19 pandemic, suggesting health-care restrictions imposed at that time did not lead to delayed diagnoses.

The study, published on Monday in the Canadian Medical Association Journal, compared detection rates before and during the early phase of the pandemic, or between March 2016 and November 2020.

It included all patients entered into the Cancer in Young People in Canada registry who were younger than 15 years old at the time of their cancer diagnosis, were diagnosed with a neoplasm — or an abnormal mass of tissue — as per the International Classification of Childhood Cancer, and diagnosed and received treatment at one of 17 paediatric haematology-oncology centres in Canada.

"Our findings suggest that among children in Canada, cancer diagnosis was not delayed during the pandemic, unlike findings described in previous reports," Dr. Marie-Claude Pelland-Marcotte, an oncologist at CHU de Québec-Université Laval, and her co-authors wrote in their study.

"Although access to emergency departments markedly dropped during the pandemic, there may have been less reluctance by families and health-care professionals to access health care for serious symptomatology."

The authors also found "no significant differences in the proportion of patients enrolled in a clinical trial, presenting with metastatic disease or who died within 30 days of presentation."

The study comes amid reports throughout much of the pandemic of delayed procedures and screenings due to pandemic-related lockdowns and restrictions — and concerns about the onset of more advanced stages of disease as a result.

The researchers cite evidence from other countries, namely the Netherlands and United Kingdom, which showed as much as a 50 per cent reduction in cancer incidence in adults after March 2020.

The Canadian study cautioned that there may be further changes in cancer detection and outcomes in the long term, given the study only looked at the first nine months of the COVID-19 pandemic.

"Although these results are reassuring, continued surveillance is necessary to ascertain potential long-term negative effects of the COVID-19 pandemic among children with cancer," the researchers say.

Other studies in adults also found decreases in new cancer diagnoses, visits, therapies and surgeries, the researchers note, "raising concerns about potential excess cancer mortality in the upcoming years."

They say this may be explained, in part, by the suspension or reduction of cancer screenings, such as mammography, colonoscopy and cervical cytology by up to 90 per cent.

A study in Japan of 123 patients with colorectal cancer also reported significantly more cases of complete intestinal obstruction, suggesting that detection delays may have contributed to diagnoses at later stages of the disease.

"It is unclear whether these findings apply to childhood cancer because cancer screening is not part of routine paediatric care, and early detection may not be as important in childhood cancer than in its adult counterpart," the authors write.