Point A vs. HR-CTV D90in MRI-based cervical brachytherapy of small and large lesions.
To evaluate the dosimetric benefits of MRI-based brachytherapy in small and large high-risk clinical target volume (HR-CTV) in cervical cancer.



Twenty-eight fractions obtained from sixteen cervical cancer patients treated with MRI-based high-dose-rate brachytherapy with standard tandem and ovoid applicators were used; original fractions were optimized to HR-CTV D90. Fractions were separated based on the median volume into small and large (HR-CTV <25 cm3or >25 cm3) lesion groups. Retrospective plans prescribed to Point A were created for each fraction. D0.1 cc, D2 cc, and International Commission of Radiation Unit and Measurements (ICRU) points were used to compare Point A vs. HR-CTV D90plans for bladder, rectum, and sigmoid.



In the small lesion group, Point A plans vs. HR-CTV D90plans had significantly higher D0.1 cc, D2 cc, and ICRU points for bladder, rectum, and sigmoid (p < 0.05). In the large lesion group, there was no significant difference between Point A and HR-CTV D90plans for D0.1 cc, D2 cc, and ICRU points to the organs at risk (OARs).



The dosimetric advantages to OARs offered by MRI-based brachytherapy with prescription to HR-CTV D90compared to Point A is most distinct for patients with smaller HR-CTV (<25 cm3). This study demonstrates sufficient tumor coverage with lower doses to OARs in HR-CTV D90vs. Point A plans in the small lesion group. These improvements were not seen in the large lesion group, indicating a lesser dosimetric advantage of HR-CTV D90compared to Point A planning when the cervical lesion is >25 cm3. Incorporation of interstitial needles for patients with larger HR-CTV is likely the best method to decrease dose to OARs and improve tumor coverage.
Department of Radiation Oncology, Loyola University, Chicago, IL.
Grant
G
Harmon
Department of Radiation Oncology, Loyola University, Chicago, IL.
Abbie
A
Diak
Department of Radiology, Loyola University, Chicago, IL.
Steven M
SM
Shea
Department of Radiology, Loyola University, Chicago, IL.
Joseph H
JH
Yacoub
Department of Radiation Oncology, Loyola University, Chicago, IL.
William
W
Small
Department of Radiation Oncology, Loyola University, Chicago, IL. Electronic address: mharkenrider@lumc.edu.
Matthew M
MM
Harkenrider
D000368:Aged; D001918:Brachytherapy / Q000379:methods*; D012809:Colon, Sigmoid / Q000528:radiation effects; D005260:Female; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods; D058958:Organs at Risk; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D012007:Rectum / Q000528:radiation effects; D012189:Retrospective Studies; D001743:Urinary Bladder / Q000528:radiation effects; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*
Cervical cancer; HR-CTV D(90); MRI-based brachytherapy; Point A; Tumor size