TY - JOUR
T1 - Dosimetric comparison of library of plans and online MRI-guided radiotherapy of cervical cancer in the presence of intrafraction anatomical changes
AU - Visser, J.
AU - de Boer, P.
AU - Crama, K. F.
AU - van Kesteren, Z.
AU - Rasch, C. R. N.
AU - Stalpers, L. J. A.
AU - Bel, A.
PY - 2019
Y1 - 2019
N2 - Background: Online magnetic resonance imaging (MRI)-guided radiotherapy of cervical cancer has the potential to further reduce dose to organs at risk (OAR) as compared to a library of plans (LOP) approach. This study presents a dosimetric comparison of an MRI-guided strategy with a LOP strategy taking intrafraction anatomical changes into account. Methods: The 14 patients included in this study were treated with chemo radiation at our institute and received weekly MRIs after informed consent. The MRI-guided strategy consisted of treatment plans created on the weekly sagittal MRI with 3 mm and 5 mm planning target volume (PTV) margin for clinical target volume (CTV) cervix-uterus (MRI-3mm and MRI-5mm). The plans for the LOP strategy were based on interpolations of CTV cervix-uterus on pretreatment full and empty bladder scans. Dose volume histogram (DVH) parameters were compared for targets and OARs as delineated on the weekly transversal MRI, which was acquired on average 10 min after the sagittal MRI. Results: For the MRI-5mm strategy D98% of the high-risk CTV was at least 95% for all weekly MRIs of all patients, while for the LOP and MRI-3mm strategy this requirement was not satisfied for at least one weekly MRI for 1 and 3 patients, respectively. The average reduction of the volume of the reference dose (95% of the prescribed dose) as compared to the LOP strategy was 464 cm3 for the MRI-3mm strategy, and 422 cm3 for the MRI-5mm strategy. The bowel bag constraint V40Gy < 350 cm3 was violated for 13 patients for the LOP strategy and for 5 patients for both MRI-3mm and MRI-5mm strategy. Conclusions: With online MRI-guided radiotherapy of cervical cancer considerable sparing of OARs can be achieved. If a new treatment plan can be generated and delivered within 10 min, an online MRI-guided strategy with a 5 mm PTV margin for CTV cervix-uterus is sufficient to account for intrafraction anatomical changes. Trial registration: NL44492.018.13.
AB - Background: Online magnetic resonance imaging (MRI)-guided radiotherapy of cervical cancer has the potential to further reduce dose to organs at risk (OAR) as compared to a library of plans (LOP) approach. This study presents a dosimetric comparison of an MRI-guided strategy with a LOP strategy taking intrafraction anatomical changes into account. Methods: The 14 patients included in this study were treated with chemo radiation at our institute and received weekly MRIs after informed consent. The MRI-guided strategy consisted of treatment plans created on the weekly sagittal MRI with 3 mm and 5 mm planning target volume (PTV) margin for clinical target volume (CTV) cervix-uterus (MRI-3mm and MRI-5mm). The plans for the LOP strategy were based on interpolations of CTV cervix-uterus on pretreatment full and empty bladder scans. Dose volume histogram (DVH) parameters were compared for targets and OARs as delineated on the weekly transversal MRI, which was acquired on average 10 min after the sagittal MRI. Results: For the MRI-5mm strategy D98% of the high-risk CTV was at least 95% for all weekly MRIs of all patients, while for the LOP and MRI-3mm strategy this requirement was not satisfied for at least one weekly MRI for 1 and 3 patients, respectively. The average reduction of the volume of the reference dose (95% of the prescribed dose) as compared to the LOP strategy was 464 cm3 for the MRI-3mm strategy, and 422 cm3 for the MRI-5mm strategy. The bowel bag constraint V40Gy < 350 cm3 was violated for 13 patients for the LOP strategy and for 5 patients for both MRI-3mm and MRI-5mm strategy. Conclusions: With online MRI-guided radiotherapy of cervical cancer considerable sparing of OARs can be achieved. If a new treatment plan can be generated and delivered within 10 min, an online MRI-guided strategy with a 5 mm PTV margin for CTV cervix-uterus is sufficient to account for intrafraction anatomical changes. Trial registration: NL44492.018.13.
UR - https://www.scopus.com/inward/record.uri?partnerID=HzOxMe3b&scp=85068909590&origin=inward
UR - https://www.ncbi.nlm.nih.gov/pubmed/31300000
U2 - https://doi.org/10.1186/s13014-019-1322-0
DO - https://doi.org/10.1186/s13014-019-1322-0
M3 - Article
C2 - 31300000
SN - 1748-717X
VL - 14
JO - Radiation oncology (London, England)
JF - Radiation oncology (London, England)
IS - 1
M1 - 126
ER -