2Department of Radiation Oncology, İstanbul University Cerrahpaşa Faculty of Medicine, İstanbul-Türkiye DOI : 10.5505/tjo.2017.1589 OBJECTIVE
The extent of previously published studies comparing static intensity-modulated radiotherapy (IMRT) and volumetric modulated arc therapy (VMAT) in the adjuvant setting of endometrial cancer is limited and reports do not cover the whole landscape of today"s clinical practice. The aim of this study was to compare these treatment techniques.
METHODS
Using 12 image sets, VMAT with double arcs and IMRT with 7 fields were planned. The femoral heads,
rectum, bladder, iliac bone marrow, and bowels were contoured as organs at risk (OARs). Planned treatment
volume (PTV) was prescribed to be 45 gray (Gy). Target and OAR parameters, conformity, and
homogeneity indices were evaluated. P value under 0.05 was considered statistically significant.
RESULTS
Objectives for target volumes were achieved. No significant differences were found in conformity index,
maximum dose (Dmax), or integral dose. Homogeneity index was better with IMRT (1.06 vs. 1.07;
p<0.01). Dose received by 2% volume of PTV (D2%), D5%, the volume receiving 107% of prescribed dose
(V107%), and V105% were lower with IMRT (p<0.05). PTV D98%, percent volume receiving ≥45 Gy (V45 Gy),
and clinical target volume V45 Gy were higher with VMAT (p<0.05). Regarding OARs, only rectum V40
Gy, rectum PTV V40 Gy, and dose volume parameter D2cc were lower with VMAT (p<0.05). VMAT was
superior with respect to monitor units and beam-on time per fraction: 465 vs. 1689 and 166 vs. 338
seconds, respectively (p<0.001).
CONCLUSION
Static IMRT is superior to VMAT regarding homogeneity, Dmax and OAR sparing, except for the rectum
and the bladder. However, it is a marginal benefit with small differences. VMAT remains an attractive
solution due to low number of monitor units needed and shorter treatment duration, which allows
more time for patient imaging and positioning.