Lung Dose Measured on Postradioembolization 90Y PET/CT and Incidence of Radiation Pneumonitis

Radiation pneumonitis is a rare but possibly fatal side effect of Y-90 radioembolization. It may occur 1-6mo after therapy, if a significant part of the Y-90 microspheres shunts to the lungs. In current clinical practice, a predicted lung dose greater than 30 Gy is considered a criterion to exclude patients from treatment. However, contrasting findings regarding the occurrence of radiation pneumonitis and lung dose were previously reported in the literature. In this study, the relationship between the lung dose and the eventual occurrence of radiation pneumonitis after Y-90 radioembolization was investigated. Methods: We retrospectively analyzed 317 Y-90 liver radioembolization procedures performed during an 8-y period (February 2012 to September 2020). We calculated the predicted lung mean dose (LMD) using Tc-99m-MAA planar scintigraphy (LMDMAA) acquired during the planning phase and left LMD (LMDY-90) using the Y-90 PET/CT acquired after the treatment. For the lung dose computation, we used the left lung as the representative lung volume, to compensate for scatter from the liver moving in the craniocaudal direction because of breathing and mainly affecting the right lung. Results: In total, 272 patients underwent Y-90 procedures, of which 63% were performed with glass microspheres and 37% with resin microspheres. The median injected activity was 1,974 MBq (range, 242-9,538 MBq). The median LMDMAA was 3.5 Gy (range, 0.2-89.0 Gy). For 14 procedures, LMDMAA was more than 30 Gy. Median LMDY-90 was 1 Gy (range, 0.0-22.1 Gy). No patients had an LMDY-90 of more than 30 Gy. Of the 3 patients with an LMDY-90 of more than 12 Gy, 2 patients (one with an LMDY-90 of 22.1 Gy and an LMDMAA of 89 Gy; the other with an LMDY-90 of 17.7 Gy and an LMDMAA of 34.1 Gy) developed radiation pneumonitis and consequently died. The third patient, with an LMDY-90 of 18.4 Gy (LMDMAA, 29.1 Gy), died 2 mo after treatment, before the imaging evaluation, because of progressive disease. Conclusion: The occurrence of radiation pneumonitis as a consequence of a lung shunt after Y-90 radioembolization is rare (<1%). No radiation pneumonitis developed in patients with a measured LMDY-90 lower than 12 Gy.

Automated summary

This study investigated the relationship between lung dose and the occurrence of radiation pneumonitis after Y-90 radioembolization. The results showed that no radiation pneumonitis developed in patients with a measured lung mean dose (LMDY-90) lower than 12 Gy.