The Effect of Radiotherapy Technique on Carotid Artery Dose in Patients with Early Stage Glottic Larynx Cancer

Abstract

Objective: The aim of this study was to compare two radiotherapy techniques in early stage glottic laryngeal cancer patients in terms of radiotherapy dose applied to the carotid artery.

Material - Methods: In this study, we included 10 early-stage (T1/2) glottic larynx cancer patients. Both intensity-modulated radiotherapy (IMRT) and 3-dimension conformal radiotherapy (3DCRT) treatment plans were prepared for each patient. Treatment volumes (CTV, PTV) were created for all patients. The entire larynx was described as CTV to include both false and true vocal cords, anterior-posterior commissures, arytenoids, aryepiglottic folds, subglottic region. For planning target volüme (PTV), while 5-mm was added to CTV in all directions, 3-mm margin was given to protect the carotid artery and spinal cord in posterolaterally. Spinal cord and carotid artery were contoured as the organ at risk (OAR). The doses of the target volumes, the OAR volumes, the homogeneity index (HI) were compared.

Results: PTV parameters (Dmin, Dmean, Dmax, D90, D95) was compared in the 2 different technique.  IMRT in comparison to 3DCRT significantly reduced the high-dose volumes (V30, V35, V50) of carotid artery (p < 0.001), but not to the low dose volume (V10). CI was similar (0.9 vs. 0.9, p = 0.3) compared to 3DCRT. However, HI was significantly improved with IMRT (0.1 vs. 0.08, p < 0.001). The maximum dose of the spinal cord was lower in 3DCRT compared to IMRT (18 Gy vs. 44Gy).

Conclusion: IMRT is a superior radiotherapy (RT) technique in patients with T1/T2 glottic cancer in terms of protecting carotid artery.

Keywords

• Radiotherapy,glottic cancer,carotid artery,3DCRT,IMRT

Erken Evre Glottik Larenks Kanserli Hastalarda Radyoterapi Tekniğinin Karotis Arter Dozu Üzerine Etkisi

Abstract

Amaç: Bu çalışmanın amacı, erken evre glottik larenks kanser tanılı hastalarda iki radyoterapi tekniğinin karotis arter dozları açısından karşılaştırılmasıdır.

Gereç - Yöntemler: Bu çalışmaya, 10 erken evre (T1 / 2) glottik larenks kanser tanılı hastayı dahil ettik. Her bir hasta için hem yoğunluk ayarlı radyoterapi (YART) hem de 3 boyutlu konformal radyoterapi (3BKRT) tedavi planları hazırlandı. Tüm hastalar için tedavi volümleri (CTV, PTV) oluşturuldu. Tüm larinks, gerçek ve yalancı vokal kordlar, anterior-posterior komissürler, aritenoidler, aryepiglottik kıvrımlar, subglottik bölge dahil edilecek şekilde klinik hedef volüm (CTV) olşturuldu. Planlanan hedef volümü (PTV) oluşturmak için, tüm yönlerde CTV'ye 5 mm eklenirken, karotis arter ve spinal kordu korumak adına posterolateral yönde 3 mm'lik marj verildi. T1/T2 glottik kanserlerde lenfatik nodal metastaz riski çok düşük olduğu için, elektif nodal ışınlama yapılmadı. Spinal kord ve karotis arterler kritik organlar (OAR) olarak konturlandı. Hedef hacim dozları, OAR hacimleri, homojenlik indeksi (HI) karşılaştırıldı. Ek olarak, karotis arter için V30 <% 20, V10 <% 50 değerlendirildi ve spinal kordun maksimum dozu 45Gy ile sınırlandırıldı. Conformite indeksi (CI) hesaplandı. İstatistiksel analiz için Mann Whitney testi kullanıldı ve p <0.05 anlamlı kabul edildi.

Bulgular: PTV parametreleri (Dmin, Dmean, Dmax, D90, D95) iki farklı teknikte karşılaştırıldı. 3BKRT’ye kıyasla YART, karotis arterde yüksek doz hacimlerini (V30, V35, V50) belirgin olarak düşürürken (p < 0.001), düşük doz hacimleri (V10) her iki teknikte de yüksek seyretti. Her iki teknikte de CI benzer olup (0.9 vs. 0.9, p = 0.3), HI YART’de daha iyiydi (0.1 vs. 0.08, p < 0.001). Spinal kord maksimum dozları 3BKRT’de daha düşüktü (18 Gy vs. 44Gy).

Sonuç: IMRT, T1 / T2 glottik kanserli hastalarda karotis arterin korunması açısından üstün bir radyoterapi (RT) tekniğidir.

Keywords

• Radyoterapi,Glottik kanser,Karotid arter,3BKRT,IMRT

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