# The newest treatments have not existed long enough for their late effects to appear

Source: https://onco.cc/bottlenecks/rejuv-agenda-latency-outruns-the-evidence/  
OnCo record `rejuv-agenda-latency-outruns-the-evidence` (Bottleneck). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A second cancer after radiotherapy can take forty years to appear. Immunotherapy and antibody-drug conjugates have been in first-line use for a few. Being told a new drug has no late effects usually means nobody has been followed long enough to see one.

## Summary

The second-cancers facet of this round wrote the sentence that this record exists to generalise: a reader who is told that a new drug has no second cancer risk should know that the usual reason is that nobody has been followed long enough to see one.

The arithmetic cuts both ways. Whether the smaller radiotherapy fields of the last twenty years have lowered the forty-year second cancer rate is not known, because nobody treated with them has yet been followed for forty years, and saying otherwise would be a guess. The risk for a girl irradiated to the chest today should be lower than for one irradiated in 1975, though by how much is not measurable because the latency has not elapsed. Whether the immunotherapies and antibody-drug conjugates now in first-line use carry any such risk is not yet measurable for the same reason. Follow-up of commercial CAR-T cohorts is still short relative to the latency of second cancers, and the FDA's 2024 labelling action on secondary T-cell malignancy states no incidence and does not attribute these malignancies to vector integration. Much of the long-term data after transplant comes from older conditioning regimens and may not describe current practice, and the largest survival cohort describes transplants performed before 2004.

This cuts against both optimism and alarm. It is the reason a survivor cannot be reassured that a new drug is clean, and equally the reason a scare about a new drug's late effects usually cannot be substantiated. The regulatory response in gene-modified cell therapy has been to require fifteen years of long-term follow-up, and the transplant facet notes the honest limit of that too: no randomised evidence exists, or could exist, on whether being followed up for fifteen years improves an individual's outcome, and loss to follow-up is the known failure mode.

What would change it is not a trial but an infrastructure: cohorts assembled at the time of treatment with the exposure recorded in a form that can still be queried in thirty years, and a registry linkage that does not depend on anyone remembering to follow up.

## Fields

- Kind: Bottleneck
- Last checked: 2026-10-02
- Tags: rejuvenation; survivorship; open-problem; second-cancers; latency
- Stage: trials
- Severity: major
- Metrics: Mandated long-term follow-up for gene-modified cell therapy products: Up to 15 years, as non-binding guidance (OnCo transplant facet, rejuv-tx-gene-modified-follow-up); What the FDA's 2024 CAR-T labelling action states about incidence of secondary T-cell malignancy: No incidence is stated, and the malignancies are not attributed to vector integration (OnCo transplant facet, rejuv-tx-secondary-t-cell-malignancy); Whether smaller modern radiotherapy fields have lowered the forty-year second cancer rate: Not known: nobody treated with them has been followed for forty years (OnCo second-cancers facet, rejuv-second-radiotherapy-dose-field-and-age)
- Causes: Solid second cancers after radiotherapy have latencies of two to four decades, which exceeds the working life of most research programmes.; Treatment changes faster than the latency, so by the time a regimen's late effects are measurable it is no longer the regimen in use.; Pharmacovigilance reporting describes reporting rather than incidence, so a signal cannot be turned into a rate.; Trial follow-up ends when the registration endpoint is met, and extension studies are voluntary and lose people.; Linking a modern treatment record to a cancer registry thirty years later requires identifiers and consent arrangements most countries have not built.

## Sources

- Schaapveld et al., Second cancer risk up to 40 years after treatment for Hodgkin's lymphoma (NEJM 2015): https://doi.org/10.1056/NEJMoa1505949

## Connected records

- terms: [Platinum drugs and PARP inhibitors: the newer leukaemia risk](https://onco.cc/terms/rejuv-second-platinum-and-parp-inhibitors/), [Radiotherapy and second cancers: field, dose and age at exposure](https://onco.cc/terms/rejuv-second-radiotherapy-dose-field-and-age/)
- technologies: [Long-term follow-up for gene-modified cell products: fifteen years, and why](https://onco.cc/technologies/rejuv-tx-gene-modified-follow-up/), [Second cancers after allogeneic transplant](https://onco.cc/technologies/rejuv-tx-second-cancers/), [Second cancers after childhood cancer: the risk by treatment, and why it is falling](https://onco.cc/technologies/rejuv-paed-second-cancers/), [Secondary T-cell malignancy after CAR-T, and what the FDA's 2024 action actually says](https://onco.cc/technologies/rejuv-tx-secondary-t-cell-malignancy/)
- ideas: [Enrol every new systemic therapy into a registry linkage that will still report in thirty years](https://onco.cc/ideas/idea-rejuv-second-cancer-latency-cohort-for-new-drugs/)
- bottlenecks: [Registries count diagnoses and deaths, and not what treatment left behind](https://onco.cc/bottlenecks/rejuv-agenda-late-effects-are-not-counted/)
- 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/)

---
JSON: https://onco.cc/api/v1/entities/rejuv-agenda-latency-outruns-the-evidence.json