DOSIMETRIC COMPARISON OF 3 DIFFERENT TREATMENT TECHNIQUES IN PANCREATIC CANCER RADIOTHERAPY: RETROSPECTIVE STUDY

Abstract

In our study, our aim is to treat 20 patients with pancreatic cancer who had radiotherapy, with conformal radiotherapy (3D-CRT), intensity modulated radiotherapy (IMRT), volume modulated arc therapy (VMAT) planning and comparison of the techniques in terms of dosimetric. In this study, 20 patients with primary pancreatic head tumor who were treated in our clinic between 2012-2017 were retrospectively evaluated. Five different treatment techniques were planned for each patient’s tumor, around of tumor  and regional lymph nodes, and all plans were implemented so that target volume doses would be 54/45 Gy. Plans were prepared using 6 MV X-rays for VMAT and IMRT and 15 MV X-rays for 3BKRT. Techniques were compared in terms of planned target volume doses (PTV), conformity index (CI), homogeneity index (HI), organs at risk (kidneys, spinal cord, liver). The mean CI indices VMAT 1 arc plans for PTV₅₄  and PTV₄₅ were found to be 1.16 and 1.03 for VMAT 2 arc 1.01 and 1.00. Although there was no significant difference between the two groups in terms of CI, the most appropriate CI value was found in VMAT 2 arc plans (p = 0.806 for PTV₄₅ and p = 0.595 for PTV₅₄). There was no difference in terms of CI between IMRT and 3D-CRT techniques, the best value being obtained from IMRT technique. Doses of VMAT 2 arc plans were found to be lower, although there was no statistical difference between VMAT 1 arc and VMAT 2 arc plans in terms of critical organ doses. Since pancreatic tumors are located close to critical organs such as kidneys and liver as a settlement, 3DCRT plans can be accepted in terms of liver; but the kidneys have not succeeded in terms of protection. The VMAT 2 arc technique excelled in dose sprinning, CI, HI and critical organ doses according to other techniques. Therefore, VMAT may be preferred as a treatment technique when side effects are taken into account.

Keywords

• VMAT,Pancreatic Cancer,3D-CRT,IMRT

Pankreas Kanseri Radyoterapisinde 3 Farklı Tedavi Tekniğinin Dozimetrik Karşılaştırılması: Retrospektif Çalışma

Abstract

Çalışmamızda amacımız pankreas kanseri tanısıyla radyoterapi görmüş, 20 hastaya konformal radyoterapi (3B-KRT), yoğunluk ayarlı radyoterapi (IMRT), hacimsel ayarlı ark terapi (VMAT) teknikleri ile tedavi planlaması yapılarak tekniklerin dozimetrik açıdan karşılaştırılmasıdır. Bu çalışmada 2012-2017 yılları arasında kliniğimizde tedavi görmüş, primer pankreas başı tümörü olan 20 hasta retrospektif olarak değerlendirilmiştir. Her hastaya tümör, tümör çevresi ve bölgesel lenf nodlarına yönelik 5 farklı tedavi tekniği planlanmış, tüm planlar hedef hacim dozları 54/45 Gy olacak şekilde seçilmiştir. Planlar VMAT ve IMRT için 6 MV X-ışını, 3BKRT için 6/15 MV X-ışını kullanılarak hazırlanmıştır. Planlanan hedef hacim dozları (PTV), Conformite indeksi (CI), Homojenite indeksi (HI), riskli organlar (böbrekler, spinal cord, karaciğer) açısından teknikler karşılaştırılmıştır. PTV₅₄ ve PTV₄₅ için ortalama CI indeksleri VMAT 1 ark planlarında sırasıyla 1,16 ve 1,03 VMAT 2 arkda ise 1,01 ve 1,00 bulunmuştur. CI açısından iki grup arasında anlamlı fark olmamasına rağmen en uygun CI değeri VMAT 2 ark planlarında bulunmuştur (PTV₄₅ için p=0,806-PTV₅₄ için p=0,595). IMRT ile 3B-KRT teknikleri arasında CI açısından fark bulunamamış, en uygun değer IMRT tekniğinden elde edilmiştir. Kritik organ dozları açısından VMAT 1 ark ve VMAT 2 ark planları arasında istatistiksel farklılık olmamasına rağmen VMAT 2 ark planlarının dozları daha düşük bulunmuştur. Pankreas tümörleri yerleşim yeri olarak böbrekler ve karaciğer gibi kritik organlara yakın oluşundan 3BKRT planları karaciğer açısından kabul edilebilir; ancak böbrekleri koruma açısından yeterli değildir. VMAT 2 ark tekniği diğer tekniklere göre doz sarımı, CI, HI ve kritik organ dozlarında üstünlük sağlamıştır. Bu yüzden yan etkiler göz önüne alındığında tedavi tekniği olarak VMAT tercih edilebilir.

Keywords

• VMAT,Pankreas Kanseri,3BKRT,IMRT

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