This dosimetric study investigated the influence of the normal tissue objective (NTO) tool in the EclipseTM radiotherapy (RT) planning system on intensity-modulated RT (IMRT) for adjuvant RT planning in endometrial cancer.
METHODS
Twenty patients, diagnosed with stage-2 endometrial cancer according to the International Federation of
Gynecology and Obstetrics, were enrolled from our Radiation Oncology department. For each patient,
three IMRT plans were devised: Without NTO (NTO-OFF), with manually configured NTO (NTO-MAN),
and with automatically configured NTO (NTO-AUTO). The plans were compared using parameters derived
from dose-volume histogram analysis, including planning target volume and organs at risk (OARs).
RESULTS
The mean conformality index was superior with NTO-MAN (0.76±0.05) compared to NTO-AUTO
(0.72±0.03, p=0.001) and NTO-OFF (0.62±0.02, p=0.000). IMRT with NTO-MAN provided enhanced
OAR protection, particularly for the bladder (V45=32.84±2.03 vs. 37.03±1.55, p=0.000) and rectum
(V30=56.18±2.05 vs. 60.50±3.86, p=0.000), compared to NTO-AUTO. The dose constraints for the
bladder and rectum were not exceeded in any patient treated with NTO-MAN but exceeded in 19 (95%)
and 9 (45%) patients, respectively, with NTO-AUTO.
CONCLUSION
The manual NTO tool resulted in greater conformality and OAR protection. Therefore, we recommend
the use of manual NTO in adjuvant IMRT planning for endometrial cancer patients.