Effect of dose rate on pulmonary toxicity in patients with hematolymphoid malignancies undergoing total body irradiation

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.

Effect of changes in monitor unit rate and energy on dose rate of total marrow irradiation based on Linac volumetric arc therapy

“…The radiation toxicity of a normal organ, especially the incidence of pulmonary toxicity, is a major factor determining the prescription dose for patients with hematolymphoid malignancies [8, 11, 19, 21]. Pulmonary toxicity can significantly affect the overall survival rate.…”

“…The side effects of TBI can be extensive and include acute symptoms such as nausea and a loss of appetite, as well as infertility and secondary malignancies [10]. Pulmonary toxicity is one of the most serious, and potentially life-threatening, complications that may occur following TBI [11]. Therefore, new techniques have concentrated on providing a safer dose escalation [12, 13].…”

“…To minimize the dose rate, the patient is generally located at an extended SSD of more than 400 cm [3]. Many studies have reported that, when TBI is performed with a low dose rate, the healthy tissue exhibits less damage [8, 9, 11, 19, 20]. Especially, low dose rates (less than 6 cGy/min) can decrease the risk of pulmonary toxicity [11, 19, 21].…”

“…Many studies have reported that, when TBI is performed with a low dose rate, the healthy tissue exhibits less damage [8, 9, 11, 19, 20]. Especially, low dose rates (less than 6 cGy/min) can decrease the risk of pulmonary toxicity [11, 19, 21]. However, TMI treatments with HT or VMAT have conventionally been performed with relatively high dose rates due to limitations on the dose rate selection and the treatment location (i.e., at the isocenter).…”

Standardized flattening filter free volumetric modulated arc therapy plans based on anteroposterior width for total body irradiation

“…In particular, there has been work performed in the literature that investigates the relationship between dose rate and the incidence or lethality of pulmonary complications such as interstitial pneumonitis (IP) or radiation pneumonitis (RP). There has been prospective and retrospective evidence illustrating both an apparent dose rate effect, [10][11][12][13][14] and no statistically significant dose rate effect. [15][16][17][18][19] When considering the dataset as a whole, several problems are evident.…”