Reconsider radiation exposure from imaging during immune checkpoint inhibitor trials to reduce risk of secondary cancers in long-term survivors?

Immune checkpoint inhibitors (ICI) have improved outcomes for patients with advanced cancers, and results in increasing numbers of long-term survivors. For registration studies, progression-free survival and disease-free survival often serve as primary endpoints. This requires repeated computed tomography (CT) scans for tumour imaging which might lead to major radiation exposure.

Intestinal tumours induced in Apc(Min/+) mice by X-rays and neutrons.

Purpose: To compare the development of intestinal adenomas following neutron and X-ray exposure of Apc(Min/+) mice (Apc - adenomatous polyposis coli; Min - multiple intestinal neoplasia).

Materials And Methods: Adult mice were exposed to acute doses of X-rays or fission neutrons. Tumour counting was undertaken 200 days later and samples were taken for Loss of Heterozygosity (LOH) analysis.

A two-mutation model of radiation-induced acute myeloid leukemia using historical mouse data.

From studies of the atomic bomb survivors, it is well known that ionizing radiation causes several forms of leukemia. However, since the specific mechanism behind this process remains largely unknown, it is difficult to extrapolate carcinogenic effects at acute high-dose exposures to risk estimates for the chronic low-dose exposures that are important for radiation protection purposes. Recently, it has become clear that the induction of acute myeloid leukemia (AML) in CBA/H mice takes place through two key steps, both involving the Sfpi1 gene.

Microsatellite instability in radiation-induced murine tumours; influence of tumour type and radiation quality.

Purpose: To investigate microsatellite instability (MSI) in radiation-induced murine tumours, its dependence on tissue (haemopoietic, intestinal, mammary, brain and skin) and radiation type.

Materials And Methods: DNA from spontaneous, X-ray or neutron-induced mouse tumours were used in Polymerase Chain Reactions (PCR) with mono- or di-nucleotide repeat markers. Deviations from expected allele size caused by insertion/deletion events were assessed by capillary electrophoresis.