Abstract
PurposeMediastinal radiotherapy (RT), especially when combined with bleomycin, may result in substantial pulmonary morbidity and mortality. The use of modern RT techniques like intensity-modulated radiotherapy (IMRT) is gaining interest to spare organs at risk.MethodsWe evaluated 27 patients who underwent RT for Hodgkin’s lymphoma between 2009 and 2013 at our institution. For each patient, three different treatment plans for a 30-Gy involved-field RT (IFRT) were created (anterior-posterior-posterior-anterior setup [APPA], 5‑field IMRT, and 7‑field IMRT) and analyzed concerning their inherent “normal tissue complication probability” (NTCP) for pneumonitis and secondary pulmonary malignancy.ResultsThe comparison of different radiation techniques showed a significant difference in favor of standard APPA (p < 0.01). The risk of lung toxicity was significantly higher in plans using 7‑field IMRT than in plans using 5‑field IMRT. The absolute juxtaposition showed an increase in risk for radiation pneumonitis of 1% for plans using 5‑field IMRT over APPA according to QUANTEC (Quantitative Analyses of Normal Tissue Effects in the Clinic) parameters (Burman: 0.15%) and 2.6% when using 7‑field IMRT over APPA (Burman: 0.7%) as well as 1.6% when using 7‑field IMRT over 5‑field IMRT (Burman: 0.6%). Further analysis showed an increase in risk for secondary pulmonary malignancies to be statistically significant (p < 0.01); mean induction probability for pulmonary malignoma was 0.1% higher in plans using 5‑field IMRT than APPA and 0.19% higher in plans using 7‑field IMRT than APPA as well as 0.09% higher in plans using 7‑field IMRT than 5‑field IMRT. During a median follow-up period of 65 months (95% confidence interval: 53.8–76.2 months), only one patient developed radiation-induced pneumonitis. No secondary pulmonary malignancies have been detected to date.ConclusionRadiation-induced lung toxicity is rare after treatment for Hodgkin lymphoma but may be influenced significantly by the RT technique used. In this study, APPA RT plans demonstrated a decrease in potential radiation pneumonitis and pulmonary malignancies. Biological planning using NTCP may have the potential to define personalized RT strategies
Highlights
Hodgkin’s lymphoma occurs within a relatively young mean age of onset
The comparison of dose–volume histogram (DVH) data of individual treatment plans showed a shift in the balance of tissue affection with low as well as high doses when switching from 3D-CRT to intensity-modulated radiotherapy (IMRT): Volumes irradiated with low doses from 5 to 15 Gy (V5–V15) were more prominent in median and mean when using IMRT (5-field as well as 7-field) compared with APPA
Additional analysis of the DVH showed that the volumes being affected by a specific dose when using IMRT over APPA were larger up to a dose of 19.3 Gy
Summary
Hodgkin’s lymphoma occurs within a relatively young mean age of onset. To ensure high rates of long-term survivors, combinations of chemotherapy and radiation treatment (RT)—and today immunotherapy and RT—have been proven effective in enhancing tumor control and overall survival for patients [1, 2]. The therapy itself can cause short-term complications such as pneumonitis or long-term toxicities like fibrosis or second malignancy. It can cause significant pulmonary morbidity and mortality, regarding the use of bleomycin as part of standard chemotherapy where older patients are at higher risk [3, 4]. Reducing these therapy-associated toxicities has become a crucial focus in modern lymphoma research [5,6,7]. The extent of radiation treatment dose and volume has gradually been downsized from extended field to involved field (IFRT; [12]) and subsequently to the involved site (ISRT) or even involved node radiation therapy (INRT; [13])
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