Acta Oncol Tur.. 2021; 54(2): 181-188 | DOI: 10.5505/aot.2021.15493

The Effects of Laxative Use on Rectum Volume and Doses During Radiotherapy in Patients With Prostate Cancer

Evrim Duman¹, Neslihan Atabek¹, Yýlmaz Bilek^2
1University of Health Sciences Antalya Training and Research Hospital, Department of Radiation Oncology, Antalya, Turkey
²University of Health Sciences Adana City Training and Research Hospital, Department of Radiation Oncology, Adana, Turkey

INTRODUCTION: Objective: Changes in rectum volume can affect dose delivery during prostate radiotherapy. The aim of this study was to evaluate how laxative use affected rectum volumes and doses in patients with prostate cancer treated with Volumetric Modulated Arc Therapy (VMAT).
METHODS: Material and Methods: Treatment planning computed tomography (simCT) and cone-beam computed tomography (CBCT) images collected from 20 patients with prostate cancer were retrospectively evaluated. These patients were divided into two groups as those who either used or did not use laxatives during radiotherapy. Rectum volumes were re-contoured on 160 CBCT images, and VMAT treatment plans were re-calculated to determine rectum doses.
RESULTS: Results: In all patients, CBCT images showed increased mean rectum volumes and doses relative to simCT images. Furthermore, the percent volume (Vx) of the rectum receiving 40, 50, 60, and 70 Gy doses based on CBCT results were larger than those based on simCT. The Dmean values in the treatment plans for the group with laxative use were 39 Gy on simCT images and 43 Gy on CBCT images (p = 0.009). Alternatively, in the group without laxatives, the Dmean values in the treatment plans were 40 Gy on simCT images and 44 Gy on CBCT images (p = 0.047).
DISCUSSION AND CONCLUSION: Conclusion: In patients undergoing prostate radiotherapy, rectum volume and doses increase regardless of laxative use. Although laxatives can limit volume expansion of the rectum, they do not have the expected effect on rectum doses and actually significantly increase all dosimetric parameters.

Keywords: Cone-beam computerized tomography, laxatives, prostate cancer, radiotherapy, volumetric-modulated arc therapy.

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Radyoterapi Uygulanan Prostat Kanseri Hastalarýnda Tedavi Süresince Laksatif Kullanýmýnýn Rektum Hacim ve Dozlarýna Etkisi

Evrim Duman¹, Neslihan Atabek¹, Yýlmaz Bilek^2
1Saðlýk Bilimleri Üniversitesi Antalya Eðitim ve Araþtýrma Hastanesi, Radyasyon Onkolojisi Kliniði, Antalya, Türkiye
²Saðlýk Bilimleri Üniversitesi Adana Þehir Eðitim ve Araþtýrma Hastanesi, Radyasyon Onkolojisi Kliniði, Adana, Türkiye

GÝRÝÞ ve AMAÇ: Amaç: Rektum hacim deðiþiklikleri prostat radyoterapisi sýrasýnda verilen dozu etkilemektdir. Hacimsel Ayarlý Ark Terapi (VMAT) uygulanan prostat kanseri hastalarýnda tedavi süresince laksatif kullanýmýnýn rektum hacim ve dozlarýna etkisinin deðerlendirilmesi amaçlandý.

YÖNTEM ve GEREÇLER: Gereç ve Yöntem: Kliniðimizde tedavi edilen 20 hastanýn tedavi planlama tomografi (simCT) ve koni ýþýnlý bilgisayarlý tomografi (CBCT) görüntüleri retrospektif olarak deðerlendirildi. Laksatif kullanan (L+)(n: 10) ve laksatif kullanmayan (L-)(n: 10) hastalar olacak þekilde 2 grup belirlendi. Toplam 160 tane CBCT görüntüsünde rektum hacimleri yeniden konturlandý. Her hastanýn kendi VMAT planý kendi CBCT görüntüleri üzerinde tekrar hesaplatýlarak rektum dozlarý elde edildi.
BULGULAR: Bulgular: Tüm hastalarýn rektum hacimleri CBCT görüntülerinde simCT görüntülerine göre artýþ göstermiþtir. Belirli bir dozu alan rektum hacminin % deðeri (Vx) için simCT ve CBCT planlarý karþýlaþtýrýldýðýnda 40Gy, 50Gy, 60Gy ve 70Gy dozlarýnýn hepsi için tüm hastalarda tedavi süresince artýþ bulunmuþtur. Laksatif kullanan hasta grubunun tedavi planlarýndaki Dmean deðerleri simCT görüntülerde 39 Gy ve CBCT görüntülerde 43 Gy bulunmuþtur (p = 0.009). Alternatif olarak, laksatifleri kullanmayan hasta grubunda, tedavi planlarýndaki Dmean deðerleri simCT görüntülerinde 40 Gy ve CBCT görüntülerinde 44 Gy bulunmuþtur (p = 0.047).
TARTIÞMA ve SONUÇ: Sonuç: Prostat radyoterapisi uygulanan hastalarda tedavi sýrasýnda rektum hacmi ve aldýðý radyasyon dozu, laksatif kullanýmýndan baðýmsýz olarak, baþlangýç tedavi planýna göre artmaktadýr.

Anahtar Kelimeler: Hacimsel Ayarlý Ark Terapi, Laksatif, Prostat kanseri, Prostat radyoterapisi, koni ýþýnlý bilgisayarlý tomografi

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