Dozimetrična primerjava različnih obsevalnih tehnik za zdravljenje Hodgkinovega limfoma v medpljučju

Kos, Franc (author), Hudej, Rihard (comentor), Zadravec-Zaletel, Lorna (mentor)

Uvod: Hodgkinov limfom (HL) je maligna bolezen limfatičnega sistema. V Sloveniji je v letu 2010 za HL zbolelo 66 bolnikov, v letu 2011 pa 41. Zdravljenje bolnikov s HL poteka s sistemsko terapijo in obsevanjem (RT). RT lahko povzroča številne pozne posledice zdravljenja. Sodobne obsevalne tehnike, kot so intenzitetno modulirana radioterapija (IMRT) in volumetrična modulirana ločna radioterapija (VMAT) omogočajo visoko konformnost predpisane doze okoli tarče in večje ščitenje rizičnih organov v primerjavi s tridimenzionalno konformalno radioterapijo (3DCRT). Namen: Namen dozimetrične primerjave različnih obsevalnih tehnik pri obsevanju HL v področju medpljučja je ugotoviti, katera izmed tehnik pripomore k najnižjim prejetim dozam na rizične organe (OAR) v medpljučju ob ustrezni homogeni pokritosti tarčnih volumnov. Metode: V raziskavo je bilo vključenih 10 bolnic, ki so bile zdravljene s 3DCRT v področju medpljučja zaradi Hodgkinovega limfoma (HL) med februarjem 2011 in avgustom 2015 na Onkološkem inštitutu (OI) v Ljubljani. Za vsako od bolnic so bili izdelani obsevalni načrti v tehnikah IMRT, VMAT in B-VMAT (»butterfly« VMAT). Obsevalni načrti so bili izdelani po protokolih za načrtovanje IMRT obsevanja na OI. Parametri za pokritost načrtovalnega obsevalnega volumna (PTV) in dozno obremenitev pljuč, srca, dojk, ščitnice, požiralnika, sapnika, hrbtenjače in področja izven PTV so bili nato primerjani med obsevalnimi tehnikami. Za preverjanje statistično značilnih razlik je bil uporabljen Kruskal-Wallis test. Rezultati: Rezultati raziskave kažejo, da tehnike IMRT, VMAT in B-VMAT (CI= 0,63; 0,66; 0,56) konformneje pokrijejo PTV kot 3DCRT (CI= 0,4). Razlik v povprečni dozi znotraj PTV in razlik v homogenosti doze med obsevalnimi tehnikami ni bilo. Povprečna doza v pljučih (Dmean) je bila najnižja pri 3DCRT (4,4 Gy) in najvišja pri VMAT (7,4 Gy). Pri IMRT je Dmean znašal 6,6 Gy in pri B-VMAT 6,4 Gy. Pri dojkah je najbližje 3DCRT tehniki B-VMAT. Dmean na srce je bila pri vseh tehnikah v precej podobna (od 3,6 do 4,8 Gy). Za srce so bili parametri V10, V25, V30 nižji pri vseh moduliranih tehnikah. Izjema je B-VMAT, ki je srce najbolj obremenil pri V10 (17,1 %). Pri ščitnici, sapniku in področju izven tarče ni bilo bistvenih razlik med obsevalnimi tehnikami. Požiralnik in hrbtenjačo so modulirane tehnike manj obremenile. Zaključek: Tehnike IMRT, VMAT, B-VMAT so konformnejše pri pokrivanju PTV in omogočajo nižjo obremenitev OAR z višjimi dozami, hkrati pa z nizkimi dozami obremenijo večje področje v primerjavi s 3DCRT. Kot najbolj uravnotežena tehnika med prispevkom nizkih in visokih doz na OAR se je pokazala B-VMAT.

• Language: Slovenian
• Keywords: Hodgkinov limfom, 3DCRT, IMRT, VMAT, dozimetrična primerjava
• Work type: Master's thesis/paper
• Organization: ZF - Faculty of Health Sciences
• Year: 2017
• PID: 20.500.12556/RUL-91015
• COBISS.SI-ID: 5251435
• Publication date in RUL: 09.03.2017

Secondary language

• Language: English
• Title: Dosimetric study of different radiotherapy techniques for treating Hodgkin's lymphoma in mediastinal region

Abstract

Introduction: Hodgkin lymphoma (HL) is a malignant disease of the lymphatic system. There were 66 patients in year 2010 and 41 patients in year 2011 diagnosed with HL in Slovenia. Patients with HL are treated with systemic therapy and radiotherapy (RT). Treatment with RT can cause acute and many long-term complications. Modern RT techniques such as intensity modulated radiotherapy (IMRT) and volumetric modulated arc radiotherapy (VMAT) can conformably cover planning target volume (PTV) with prescribed dose and can better protect organs at risk (OAR). Purpose: The purpose of the dosimetric comparison is to determine which of the techniques is better in lowering doses to OAR in mediastinal region and in the same time allowing sufficiently homogeneous coverage of the PTV. Methods: The study included 10 patients who were treated with RT of mediastinal HL. Patients were treated at the Institute of Oncology Ljubljana between February 2011 and August 2015. All were treated with 3DCRT. For each of the patient treatment plans were made using IMRT, VMAT and B-VMAT ("butterfly" VMAT) techniques. All irradiation plans were made using protocols for IMRT planning at the Institute of Oncology Ljubljana. Coverage of PTV and doses to the lungs, heart, breast, thyroid, esophagus, trachea, spinal cord and the to the area outside the PTV were compared. In order to verify statistically significant difference Kruskal-Wallis test was used. Results: The results show that IMRT, VMAT and B-VMAT (CI = 0.63; 0.66; 0.56) had more conformal dose distribution over the PTV than the 3DCRT (CI = 0.4). There were no major differences in the mean doses and in the homogeneity index for the PTV. The mean lung dose (Dmean) was lowest in 3DCRT (4.4 Gy) and the highest for VMAT (7.4 Gy). In IMRT Dmean was 6.6 Gy and in B-VMAT was 6.4 Gy. Observing doses to breast, B-VMAT had the closest results to 3DCRT. Dmean of the heart was quite similar in all techniques (from 3.6 to 4.8 Gy). Parameters V10, V25, V30 for the heart were lower in modulated techniques in comparison to 3DCRT, except for B-VMAT, which was the highest in the V10 (17.1%). None of the differences were statistically significant. In the thyroid, trachea and the area outside the target there were no significant differences between RT techniques. Doses to esophagus and spinal cord were lowest in modulated techniques. Conclusion: All modern RT techniques (IMRT, VMAT, B-VMAT) are better in conformably covering the PTV with prescribed dose. They can lower the percentage of OARs covered with higher doses. At the same time, they cover much higher percentage of OARs with low doses compared to 3DCRT. The most balanced technique between the contribution of low and high doses in OAR is B-VMAT.

• Keywords: Hodgkin's lymphoma, 3DCRT, IMRT, VMAT, dosimetric study