Abstract
BackgroundThis study evaluated the effect of radiation dose rate in patients with hematolymphoid malignancies undergoing myeloablative conditioning with total body irradiation (TBI), for hematopoietic stem cell transplantation.MethodsThe incidence of pulmonary toxicity (PT) and treatment efficacy were compared between the conventional (≥ 6 cGy/min) and reduced dose rate (< 6 cGy/min). Seventy-seven patients receiving once-daily TBI between 2000 and 2016 were reviewed. We compared the cumulative rate of PT, overall survival (OS), relapse, and transplantation-related mortality (TRM) between conventional (n = 54) and reduced (n = 23) groups. Factors associated with PT were assessed in the presence of competing risks.ResultsThe median follow-up time was 40.7 months, and PT occurred in 50 patients (64.9%). On multivariate analyses, the groups classified by the dose rate (P = 0.010), total dose (P = 0.025), and conditioning regimen (P = 0.029) were significant factors for the development of PT. OS was significantly reduced when PT occurred (P < 0.001). However, the OS, relapse, and TRM were not different between the two groups.ConclusionsIn summary, about two-thirds of the patients undergoing daily TBI experienced PT, which affected OS. Therefore, reducing the dose rate (less than 6 cGy/min) of TBI can decrease the risk of PT, without compromising the treatment efficacy.
Highlights
This study evaluated the effect of radiation dose rate in patients with hematolymphoid malignancies undergoing myeloablative conditioning with total body irradiation (TBI), for hematopoietic stem cell transplantation
A large retrospective review of 932 patients undergoing TBI followed by hematopoietic stem cell transplantations (HSCT) disclosed that a dose rate less than 6 cGy/min was correlated with a decreased incidence of pulmonary toxicity (PT) [8]
One retrospective study found that using a TBI dose rate of less than 4 cGy/min was significantly associated with reducing the incidence of interstitial pneumonitis [21]
Summary
This study evaluated the effect of radiation dose rate in patients with hematolymphoid malignancies undergoing myeloablative conditioning with total body irradiation (TBI), for hematopoietic stem cell transplantation. Total body irradiation (TBI)-based myeloablative conditioning, followed by allogeneic stem cell transplantation, is conducted for patients with high-risk or relapsed hematolymphoid malignancies [1,2,3]. TBI has been used in 46% to 53% of allogeneic hematopoietic stem cell transplantations (HSCT) as a preconditioning component, with other chemotherapeutic agents [4]. PT is a life-threatening problem after TBI, followed by bone marrow transplantation (BMT), which together, account for 25–50% non-relapse deaths in prior studies [2, 8,9,10,11,12,13]
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