Evaluation of Radiation-induced Pleural Effusions after Radiotherapy to Support Development of Animal Models of Radiation Pneumonitis

Thirty-Nine Years Later: A Case Report and Literature Review of Delayed Pleural and Pericardial Effusions After Chest Radiotherapy for Non-Hodgkin Lymphoma

Radiation therapy (RT) is a common treatment for non-Hodgkin lymphoma (NHL) but can lead to long-term pulmonary and cardiovascular complications. Delayed radiotherapy-related pleural effusion (DRPE) and pericardial effusion are rare sequelae, with few cases reported. This case highlights recurrent pleural and pericardial effusions nearly 40 years after chest RT, underscoring the need for ongoing surveillance in cancer survivors. A 51-year-old female with a history of nodular sclerosing NHL in remission after RT in 1977 presented in 2016 with recurrent bilateral pleural and pericardial effusions. Despite multiple interventions, including pericardiocentesis, thoracenteses, and pleural catheter placement, her effusions persisted. An extensive workup ruled out malignancy, infection, and autoimmune causes, ultimately attributing the effusions to radiation-induced lung injury. Despite ongoing management, she was discharged to hospice care. DRPE is a diagnostic challenge due to its delayed onset, sometimes appearing decades after RT. It can present with variable pleural fluid characteristics. Radiation-induced lung injury is a known complication of thoracic RT, with risk factors including radiation dose and pre-existing pulmonary conditions. Management is symptomatic, with treatments such as NSAIDs, corticosteroids, diuretics, and pleural drainage, though outcomes vary. In this case, pleural catheter placement offered temporary relief, but recurrent effusions led to hospice care. This case highlights the need for long-term monitoring in survivors of chest RT, as delayed pulmonary and cardiovascular toxicities can arise decades later. Given the rarity of DRPE and the lack of standardized treatment, further research into protective strategies and early interventions for radiation-induced lung injury is essential to improve cancer survivors' quality of life.

Selecting the Most Relevant Mouse Strains for Evaluating Radiation-Induced Multiple Tissue Injury after Leg-Shielded Partial-Body Gamma Irradiation

Animal studies are needed that best simulate a large-scale, inhomogeneous body exposure after a radiological or nuclear incident and that provides a platform for future development of medical countermeasures. A partial-body irradiation (PBI) model using 137Cs gamma rays with hind limb (tibia) shielding was developed and assessed for the sequalae of radiation injuries to gastrointestinal tract, bone marrow (BM) and lung and among different genetic mouse strains (C57BL/6J, C57L/J, CBA/J and FVB/NJ). In this case, a marginal level of BM shielding (∼2%) provided adequate protection against lethality from infection and hemorrhage and enabled escalation of radiation doses with evaluation of both acute and delayed radiation syndromes. A steep radiation dose-dependent body weight loss was observed over the first 5 days attributed to enteritis with C57BL/6J mice appearing to be the most sensitive strain. Peripheral blood cell analysis revealed significant depression and recovery of leukocytes and platelets over the first month after PBI and were comparable among the four different mouse strains. Latent pulmonary injury was observed on micro-CT imaging at 4 months in C57L/J mice and confirmed histologically as severe pneumonitis that was lethal at 12 Gy. The lethality and radiological densitometry (HUs) dose responses were comparable to previous studies on C57L/J mice after total-body irradiation (TBI) and BM transplant rescue as well as after localized whole-thorax irradiation (WTI). Indeed, the lethal radiation doses and latency appeared similar for pneumonitis appearing in rhesus macaques after WTI or PBI as well as predicted for patients given systemic radiotherapy. In contrast, PBI treatment of C57BL/6 mice at a higher dose of 14 Gy had far longer survival times and developed extreme and debilitating pIeural effusions; an anomaly as similarly reported in previous thorax irradiation studies on this mouse strain. In summary, a radiation exposure model that delivers PBI to unanesthetized mice in a device that provides consistent shielding of the hind limb BM was developed for 137Cs gamma rays with physical characteristics and relevance to relatively high photon energies expected from the detonation of a nuclear device or accidental release of ionizing radiation. Standard strains such as C57BL/6J mice may be used reliably for early GI or hematological radiation syndromes while the C57L/J mouse strain stands out as the most appropriate for evaluating the delayed pulmonary effects of acute radiation exposure and recapitulating this disease in humans.

IPW-5371 mitigates the delayed effects of acute radiation exposure in WAG/RijCmcr rats when started 15 days after PBI with bone marrow sparing

PURPOSE

To test IPW-5371 for the mitigation of the delayed effects of acute radiation exposure (DEARE). Survivors of acute radiation exposure are at risk for developing delayed multi-organ toxicities; however, there are no FDA-approved medical countermeasures (MCM) to mitigate DEARE.

METHODS

WAG/RijCmcr female rat model of partial-body irradiation (PBI), by shielding part of one hind leg, was used to test IPW-5371 (7 and 20 mg kg-1 d-1) for mitigation of lung and kidney DEARE when started 15 d after PBI. Rats were fed known amounts of IPW-5371 using a syringe, instead of delivery by daily oral gavage, sparing exacerbation of esophageal injury by radiation. The primary endpoint, all-cause morbidity was assessed over 215 d. Secondary endpoints: body weight, breathing rate and blood urea nitrogen were also assessed.

RESULTS

IPW-5371 enhanced survival (primary endpoint) as well as attenuated secondary endpoints of lung and kidney injuries by radiation.

CONCLUSION

To provide a window for dosimetry and triage, as well as avoid oral delivery during the acute radiation syndrome (ARS), the drug regimen was started at 15 d after 13.5 Gy PBI. The experimental design to test mitigation of DEARE was customized for translation in humans, using an animal model of radiation that was designed to simulate a radiologic attack or accident. The results support advanced development of IPW-5371 to mitigate lethal lung and kidney injuries after irradiation of multiple organs.