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

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.