# The field cannot pool its own studies, because it has not agreed what to measure

Source: https://onco.cc/bottlenecks/rejuv-agenda-no-agreed-outcome-measures/  
OnCo record `rejuv-agenda-no-agreed-outcome-measures` (Bottleneck). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

On subject after subject here, the studies exist and cannot be combined, because each used a different definition, a different questionnaire or a different threshold. A prevalence that ranges from 0 to 84 per cent is a measurement problem, not a biological one.

## Summary

This gap is methodological and it is why several records on this front print a named gap where a number should be. The clearest example is kidney function after childhood cancer: reported prevalence ranges from 0 to 84 per cent across studies with no agreed outcome measure, and the paediatric facet's conclusion is that the field has not agreed what to measure, so the studies cannot be compared and no single prevalence figure is defensible.

The same pattern recurs. On time to diagnosis in adolescents and young adults, a systematic review found that the skewed distribution of the data meant comparisons between studies based on medians were difficult and combining studies within a meta-analysis was not appropriate, and the consequence is that there is no defensible average time to diagnosis for that age group. On quality of life after a stoma or limb loss, the approaches used to measure health-related quality of life were inconsistent and outcome scores varied substantially. On fear of recurrence, a major review concluded that the field had expanded somewhat haphazardly over the preceding twenty years and that consensus definitions and well-validated measures were still needed. On body image after head and neck cancer there is no pooled prevalence figure at all. On bowel function after pelvic radiotherapy, prevalence is reported very differently across studies and no single cohort figure was defensible. On nails after chemotherapy, an incidence range of 0 to 44 per cent says more about how it is measured than how often it happens. On cognition, self-report and neuropsychological testing diverge, which is a disagreement about what the outcome even is.

The fix is known and unglamorous. Core outcome sets, which specify a minimum set of outcomes and the instruments to measure them, have been developed for other fields and change what can be pooled within about a decade. They cost little, need no new biology, and require that a critical mass of investigators agree to use them. The reason they are missing here is the same reason most things on this front are missing: no sponsor, no mandate and no funder asking for one.

## Fields

- Kind: Bottleneck
- Last checked: 2026-10-02
- Tags: rejuvenation; survivorship; open-problem; outcomes; methods
- Stage: data-knowledge
- Severity: major
- Metrics: Reported prevalence of kidney impairment after childhood cancer across studies: 0 to 84 per cent, with no agreed outcome measure (OnCo paediatric facet, rejuv-paed-kidneys); Reported incidence of nail changes after chemotherapy: 0 to 44 per cent (OnCo body facet, nail-changes-after-chemotherapy); Meta-analysis of time to diagnosis in adolescents and young adults: Not appropriate to combine studies, per the systematic review's own conclusion (OnCo paediatric facet, rejuv-ayac-diagnostic-delay)
- Causes: Each specialty measuring a late effect brought its own instrument from its own field, and none was designed for survivors.; No funder requires a core outcome set, and no journal requires that a study report one.; Patient-reported and clinician-measured outcomes diverge for several of these effects, and the field has not decided which is the outcome.; Studies are small and single-centre, so the cost of an idiosyncratic measure is invisible to the people who bear it.; Retrospective cohorts measure whatever was recorded at the time, which was not chosen for this purpose.

## Sources

- Hudson et al., Clinical ascertainment of health outcomes among adults treated for childhood cancer (JAMA 2013;309:2371): https://doi.org/10.1001/jama.2013.6296

## Connected records

- technologies: [A changed face and voice: body image after head and neck cancer treatment](https://onco.cc/technologies/rejuv-mind-visible-difference-head-and-neck/), [Bowel function after pelvic radiotherapy](https://onco.cc/technologies/bowel-after-pelvic-radiotherapy/), [Fear that the cancer will come back: how common it is, and when it stops being ordinary worry](https://onco.cc/technologies/rejuv-mind-fear-of-recurrence/), [How long it takes to diagnose cancer in a young person, and what the evidence actually says](https://onco.cc/technologies/rejuv-ayac-diagnostic-delay/), [Kidneys after cisplatin, ifosfamide, radiotherapy and nephrectomy in childhood](https://onco.cc/technologies/rejuv-paed-kidneys/), [Living with a stoma, and living after an amputation](https://onco.cc/technologies/rejuv-mind-body-after-stoma-and-limb-loss/), [Nails after chemotherapy: lifting, ridges and discolouration](https://onco.cc/technologies/nail-changes-after-chemotherapy/), [Thinking and memory after cancer treatment: what is measurable, and what helps](https://onco.cc/technologies/cognitive-impairment-after-cancer-treatment/)
- ideas: [Agree what to measure, so the next systematic review can pool rather than narrate](https://onco.cc/ideas/idea-rejuv-core-outcome-set-for-late-effects/), [Give survivorship interventions a shared control arm](https://onco.cc/ideas/idea-rejuv-survivorship-platform-trial/), [Patient-reported side-effects (PRO-CTCAE) collected and published in every registrational trial](https://onco.cc/ideas/idea-moon-pro-ctcae-in-every-pivotal-trial/)
- collections: [International Guideline Harmonization Group for late effects of childhood cancer](https://onco.cc/collections/ighg/)
- roadmaps: [Recovery and rejuvenation roadmap: cure is not enough → survivorship gets a name → the cohorts that measured the cost → exercise proven as treatment → biological ageing measured and sold → repair, if anyone funds it](https://onco.cc/roadmaps/rejuvenation-roadmap/)
- fronts: [Recovery & Rejuvenation](https://onco.cc/fronts/rejuvenation/), [Supportive Care & Survivorship](https://onco.cc/fronts/supportive-care/)

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