Significant improvements in five-year childhood cancer survival are most likely a result of more effective treatment rather than changes in stage at diagnosis, Australian researchers suggest.
Their retrospective, observational cohort study compared 8242 children (55% boys) aged 0–14 diagnosed with cancer between 2000-2008 (44%) and 2009-2017 (56%) using data from the population-based Australian Childhood Cancer Registry.
Half of the cases were diagnosed within the 0–4 age group.
The most common cancer was acute lymphoblastic leukaemia, accounting for one-third of cases (35%) followed by astrocytoma (14%) and neuroblastoma (9%).
There was no evidence of any differences in the distribution of cases by sex, age group or type of cancer when stratified by period of diagnosis.
The researchers used the staging system of the Toronto Paediatric Cancer Stage Guidelines and followed patients for five years or until 31 December 2020.
Writing in Acta Oncologica [link here], the researchers said almost all children with retinoblastoma (99%) or astrocytoma (98%) had localised/regional disease at diagnosis, whereas 58% of cases of neuroblastoma were metastatic at diagnosis.
They observed a significant shift in stage at diagnosis for retinoblastoma, with the proportion diagnosed at stage 0 (where the tumour is confined to the globe and enucleation is not performed) increasing from 26% during 2000-2008 to 37% during 2009-2017 and a corresponding decrease from 71% to 58% for stage I.
For hepatoblastoma, there was an increase over time in the percentage of children diagnosed with metastatic disease from 22% to 38% across diagnosis periods.
Overall, there were 1268 deaths (15%) recorded within five years of diagnosis, although the percentage varied significantly by diagnostic period, from 20% of cases for the period 2000–2008 compared to 12% of cases for 2009–2017.
The researchers observed significant improvements in five-year stage-specific survival for children diagnosed during 2009–2017 for multiple cancer types.
Advanced solid cancers were associated with the greatest gains, having had low survival rates in the earlier period, namely stage IV rhabdomyosarcoma (five-year adjusted mortality hazard ratio 0.38), metastases to the spine (stage M3) for medulloblastoma (0.41) and metastatic neuroblastoma excluding stage MS (0.61).
Smaller, but still significant, improvements in five–year survival occurred for children with stage CNS1 acute lymphoblastic leukaemia (HR 0.54) and localised astrocytoma (HR 0.60). Findings also showed an increase in survival among children with stage III/yIII renal tumours (89% to 99%; HR 0.10), the authors noted.
Non-statistically significant results showed reduced mortality risk for stage I/II non–Hodgkin lymphoma, stage L1 neuroblastoma, stage I/yI renal tumours, localised hepatoblastoma, stage I rhabdomyosarcoma and stage I non–rhabdomyosarcoma soft tissue sarcoma, but increased risk for stage MS neuroblastoma.
The researchers, led by the Viertel Cancer Research Centre, Cancer Council Queensland, Brisbane, said their study was the first to report changes over time in stage-specific incidence and survival for childhood cancers at a population level.
“Our results show that the distribution of stage at diagnosis has changed very little over time for children with cancer in Australia, with the exception of retinoblastoma and hepatoblastoma,” the authors concluded.
“Improvements in overall survival for many types of childhood cancer over the last two decades are therefore unlikely to be explained by a shift from more advanced to less advanced disease at diagnosis; rather, the observed increases are at a stage-specific level and reflect the implementation of more effective therapies developed through large clinical trials.
“It should be noted, however, that some of these novel therapies prolong survival rather than curing patients. Therefore, it may be beneficial to consider longer-term stage-specific survival (at least 10 years from diagnosis) in future studies as the data become available.”