Comparative treatment planning study for mediastinal Hodgkin’s lymphoma: impact on normal tissue dose using deep inspiration breath hold proton and photon therapy

Abstract

Background: Late effects induced by radiotherapy (RT) are of great concern for mediastinal Hodgkin's lymphoma (HL) patients and it is therefore important to reduce normal tissue dose. The aim of this study was to investigate the impact on the normal tissue dose and target coverage, using various combinations of intensity modulated proton therapy (IMPT), volumetric modulated arc therapy (VMAT) and 3-dimensional conformal RT (3D-CRT), planned in both deep inspiration breath hold (DIBH) and free breathing (FB). Material and methods: Eighteen patients were enrolled in this study and planned with involved site RT. Two computed tomography images were acquired for each patient, one during DIBH and one during FB. Six treatment plans were created for each patient; 3D-CRT in FB, 3D-CRT in DIBH, VMAT in FB, VMAT in DIBH, IMPT in FB and IMPT in DIBH. Dosimetric impact on the heart, left anterior descending (LAD) coronary artery, lungs, female breasts, target coverage, and also conformity index and integral dose (ID), was compared between the different treatment techniques. Results: The use of DIBH significantly reduced the lung dose for all three treatment techniques, however, no significant difference in the dose to the female breasts was observed. Regarding the heart and LAD doses, large individual variations were observed. For VMAT, the mean heart and LAD doses were significantly reduced using DIBH, but no significant difference was observed for 3D-CRT and IMPT. Both IMPT and VMAT resulted in improved target coverage and more conform dose distributions compared to 3D-CRT. IMPT generally showed the lowest organs at risk (OAR) doses and significantly reduced the ID compared to both 3D-CRT and VMAT. Conclusions: The majority of patients benefited from treatment in DIBH, however, the impact on the normal tissue dose was highly individual and therefore comparative treatment planning is encouraged. The lowest OAR doses were generally observed for IMPT in combination with DIBH.

Pencil beam scanning proton therapy of Hodgkin’s lymphoma in deep inspiration breath-hold: A case series report

“…The PBS proton dose distribution presented here was superior compared to 3DCRT photons, the heart dose was reduced by 40-70% and the lung dose by 40%. This is consistent with earlier published findings [4,5].…”

“…Proton therapy for mediastinal tumours has the potential to reduce lung and heart doses compared to photon-based radiotherapy [3]. The combination of pencil beam scanning (PBS) proton therapy and deep inspiration breath-hold (DIBH) technique improves the sparing effect even further [4,5] due to favourable anatomical changes compared to free breathing (FB). Furthermore, a successfully applied DIBH technique minimizes the effect of respiratory motion on range uncertainties and interplay effects [6,7].…”

Intensity modulated proton therapy compared to volumetric modulated arc therapy in the irradiation of young female patients with hodgkin’s lymphoma. Assessment of risk of toxicity and secondary cancer induction

“…Everett [6] showed how DIBH could improve lung dosimetry but might had little impact on cardiac involvement in mediastinal lymphoma treatments. Similarly Edvardsson [8] demonstrated the benefit for lung and the limited value for breasts (with large variations depending on the individual case for the heart structures). In the present study, the CT datasets used for the planning were acquired in free breathing (due to the current clinical practice for HL in our institute) and it can be anticipated that all the dosimetric findings for lung might be further improved according to the above indications.…”

“…carcinogenesis). Simple methods based on the investigation of physical dose distributions or simple complication models, mostly at planning level, have been discussed but could only provide general indications and not individualized selection criteria [4][5][6][7][8]. The best approach to validation would be the execution of properly sized and defined clinical trials but this could be limited by ethical considerations, the time needed to obtain the results and the costs of execution.…”

Impact of radiation techniques on lung toxicity in patients with mediastinal Hodgkin’s lymphoma

“…Other studies point out that this increase of low-dose tissue irradiation might be compensated by superior target volume coverage delivered by IMRT [22,23]. The additional scientific effort has since shown other treatment modalities to effectively achieve more efficient protection of normal tissue: Both proton therapy and VMAT may be beneficial [22,24] while deep inspiration breath-hold serves as a strategy to reduce treatment toxicity over multiple modalities [22].…”