Stage of childhood cancer does not reflect survival

Blood cancers

By Mardi Chapman

5 Mar 2019

The first population-wide picture of the distribution and outcomes for childhood blood cancers in Australia by stage at diagnosis shows five-year survival is about 85–90%, even in ALL and NHL patients presenting with higher stage disease.

The study applied the Toronto Paediatric Cancer Staging Guidelines to more than 2,000 leukaemia and lymphoma cases from the Australian Childhood Cancer Registry.

It found 91% of patients with ALL had CNS1 disease using the Children’s Oncology Group (COG) staging system, 6.9% staged as CNS2 and 2.1% as CNS3. Respective five-year survival rates were 94.1%, 89.0% and 90.3%.

The overall difference in survival by stage at diagnosis was not statistically significant (p=0.07-0.91) or borderline when comparing CNS1 with CNS2 (p=0.05).

Almost two thirds of AML cases (65.6%) were CNS- and 34.4% CNS+. Survival estimates were similar irrespective of CNS involvement (77% vs 78%, P=0.94).

“This similarity in survival irrespective of CNS involvement is at least in part because intrathecal chemotherapy has proven to be effective in the treatment of CNS disease associated with AML, but the optimal regime is yet to be determined,” the study authors said.

“Prognosis for AML is instead primarily dictated by cytogenetic and molecular characteristics at diagnosis, raising the question of whether an alternative definition of stage for children with AML that incorporates these characteristics may be of more benefit.”

The proportions of Hodgkin lymphoma patients staged by the Ann Arbor system was 16.2% IA/IB, 35.1% IIA/IIB, 19.9% IIIA/IIIB and 28.8% IVA/IVB. Respective five-year survival rates were 100%, 100%, 97.1% and 100% with no difference by stage (p=0.30).

Non-Hodgkin lymphoma staging using the St Judes-Murphy’s system showed most cases (56.1%) were stage III versus stage 1 (12.0%), II (9.6%) and IV (22.3%).

“Although the overall effect of disparities in survival by stage was not statistically significant for children with NHL (P=0.22), there was evidence of a decreasing trend in survival as stage became higher, with survival of 97% for stage I compared with 85% for stage IV (P trend = 0.04).”

Co-author Professor Joanne Aitken, from Cancer Council Queensland, told the limbic cancer registries around the world had not routinely collected staging details.

“It’s because stage is not often recorded in the medical record. But it is really important; it’s a fundamental piece of information that is really important for understanding the epidemiology of cancer. And particularly with childhood cancers, we are trying to make the collection of stage easier through the guidelines that have been developed.”

“And because childhood cancer is so rare, it’s important that data is combined within countries from states and territories but also across countries. We also want to be able to compare between low-income countries and high-income countries and not everybody has the resources that they need to be able to do that.”

She said the fact that stage did not always correlate with survival was partly due to the low numbers of high stage cancers.

“There are some cancers where there are almost no high stages so you can’t really do that comparison. But where we can do the comparison, it isn’t always the case that high stage means poor survival because high stage means the child gets more intensive treatment but at the end of the day survival is just as good.”

And stage was not the only variable.

“We are certainly thinking about adding cytogenetic and molecular details to the Toronto guidelines. Anatomic stage is also going to be very important – a fundamental as to how far the cancer has advanced at diagnosis – but there are other important things that determine prognosis such as molecular markers and other characteristics of the disease.”

Professor Aitken said the study, funded by Cancer Australia, showed Australian children had access to among the best treatment in the world.

“Five-year survivals are fantastic. We are one of the best countries in the world for childhood cancer survival.”

“This is a great step forward in being able to collect population based information on stage and we would like to continue to do this and expand this around the world so we can do international comparisons, and really start to address what are huge inequities between low income and high income countries,”  she said.

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