Dosimetric Comparison of Three-Dimensional Conformal Radiotherapy, Forward-Planned Intensity Modulated Radiotherapy and Volumetric Modulated Arc Therapy in Intact Breast Radiotherapy without Lymphatic Irradiation

INTRODUCTION: The present study aimed to determine the most suitable technique for whole breast radiotherapy after breast conserving surgery in patients without lymph node involvement; those that constitute the majority of breast cancer cases. Three-dimensional conformal radiotherapy (3DCRT), that is widely used, forward planned intensity-modulated radiotherapy (forIMRT), that is accepted to be cost-effective, and volumetric modulated arc therapy (VMAT), that has become available recently, were dosimetrically compared.
METHODS: Computed tomography simulation cross-sections of 16 patients with right breast cancer and 19 patients with left breast cancer, who had been treated with forIMRT, were used in the study. All planning was done using Eclipse 10.0 treatment planning system. A conventional scheme consisting of a total dose of 50Gy given in 25 fractions was used. The techniques were compared in terms of target volume and critical organ (ipsilateral lung, heart, contralateral breast and contralateral lung) doses.
RESULTS: We successfully achieved target coverage (TC) by all three techniques. Forward IMRT led to a higher decrease in planned target volume (PTV) maximum dose (Dmax), in comparison to 3DCRT. The best PTV dose homogeneity was achieved with VMAT. forIMRT resulted in higher reductions in all critical organ doses when compared to 3DCRT, and the decrease was significantly higher in the ipsilateral lung mean dose (Dmean) and Dmax and the volume of ipsilateral lung receiving ≥40Gy (V40), and contralateral breast Dmax and V5. Compared to the other two methods, VMAT led to a greater decrease in Dmax, V20, V30 and V40 of the ipsilateral lung and Dmax and V35 of the heart in left breast cancer patients; but led to a significant increase in Dmean, V5 and V10 of the ipsilateral lung; Dmean, Dmax, and V5 of the contralateral lung and breast, and Dmax, Dmean, V5 and V10 of the heart in right breast cancer patients; and Dmean, V5, and V10 of the heart in left breast cancer patients.
DISCUSSION AND CONCLUSION: forIMRT provides a better dosimetry than 3DCRT for intact breast radiotherapy; therefore, it should be preferred, whenever possible. More homogeneous dose distributions are achieved with VMAT. Additionally, while ipsilateral critical organ high doses decrease by VMAT, ipsilateral and contralateral critical organ low doses show a significant increase. The outcomes of this condition should be studied in clinical studies with long-term follow-up.

Lenfatik Iþýnlamanýn Yapýlmadýðý Ýntakt Meme Radyoterapisinde 3DCRT, forward-planned IMRT ve VMAT’nin Dosimetric Karþýlaþtýrmasý

GÝRÝÞ ve AMAÇ: Bu çalýþmada; meme kanseri vakalarýnýn çoðunluðunu oluþturan, lenf nodu tutulumu olmayan hastalarda, meme koruyucu cerrahi sonrasý tüm meme radyoterapisi için en uygun tekniðin araþtýrýlmasý amaçlanmýþtýr. Yaygýn kullanýlan üç boyutlu konformal radyoterapi (3DKRT), uygun maliyetli kabul edilen statik Yoðunluk Ayarlý Radyoterapi (sYART) ve yeni kullanýma giren Volümetrik Ayarlý Ark Terapi (VMAT) dozimetrik olarak karþýlaþtýrýldý.
YÖNTEM ve GEREÇLER: Çalýþmada sIMRT ile tedavi almýþ 16 sað ve 19 sol meme kanseri tanýlý hastanýn bilgisayarlý tomografi(BT) simülasyon kesitleri kullanýldý. Tüm planlamalar Eclipse 10,0 sistemi ile yapýldý. Uygulanan doz total 50Gy/25fraksiyonda, konvansiyonel þema olarak belirlendi. Teknikler hedef volüm ve kritik organ (ipsilateral akciðer, kalp, kontrlateral meme ve kontrlateral akciðer) dozlarý açýsýndan karþýlaþtýrýldý.
BULGULAR: Üç teknik de Hedef Sarýmý(TC) baþarýyla saðlamýþtýr. sYART, 3DKRT’e göre Planlanan Hedef Volüm (PTV) maksimum dozunu (Dmax) düþürmektedir. En iyi PTV doz homojenitesi VMAT ile saðlanmýþtýr. sYART tüm kritik organ dozlarýnda 3DKRT’ye göre düþüþ saðlamaktadýr ve bu düþüþ ipsilateral akciðer ortalama dozu(Dmean), Dmax, 40Gy ve üstü doz alan volüm(V40); kontrlateral meme Dmax ve V5 için istatistiksel olarak anlamlý bulunmuþtur. VMAT diðer iki yönteme göre ipsilateral akciðer Dmax, V20, V30, V40 ve sol meme kanseri hastalarýnda kalp Dmax ve V35’i düþürmüþtür; fakat ipsilateral akciðer Dmean, V5, V10; kontrlateral akciðer ve meme Dmean, Dmax, V5; sað meme ca hastalarýnda kalp Dmax, Dmean, V5, V10; sol meme kanseri hastalarýnda kalp Dmean, V5, V10’u anlamlý yükseltmiþtir.
TARTIÞMA ve SONUÇ: Ýntakt meme radyoterapisi için 3DKRT yerine sYART daha iyi dozimetri saðlamaktadýr, bu sebeple mümkün oldukça tercih edilmelidir. VMAT ile daha homojen doz daðýlýmlarý saðlanýr. Ayrýca VMAT ile ipsilateral kritik organ yüksek dozlarý düþerken, ipsilateral ve kontrlateral kritik organ düþük dozlarý anlamlý artýþ göstermektedir. Bu durumun sonuçlarý uzun takipli klinik çalýþmalar ile incelenmelidir.