Treating intact cervical cancer with intensity-modulated radiotherapy: maximized bladder-filling change and tumor extent are associated with organ motion.
Journal
Therapeut Radiol Oncol
Journal Volume
21
Journal Issue
3
Pages
211-221
Date Issued
2014
Author(s)
Abstract
Introduction: The aim of the present study is to evaluate the impact of bladder filling on uterus-cervix mobility in patients with cervical cancer and an intact uterus treated by intensity-modulated radiotherapy (IMRT). Methods and Materials: Twenty-two consecutive women with cervical cancer (FIGO stage IB-IVB) receiving pelvic IMRT were selected for analysis. Two series of treatment planning CT scans, one with a full bladder and the other with an empty bladder, were acquired. The target volumes and normal tissues were contoured on each CT scan according to the updated guidelines and staging MRI. We determined the centroid positions of the cervical tumor and uterus, then correlated the centroid displacement to the delta volume of the bladder (DVB; defined as the volume difference between full and empty urinary bladders; the maximized bladder filling change). Results: A significant mobility of the uterus-cervix according to bladder filling was observed on the superior-inferior axis only. For all patients, displacement of the uteruscervix on the superior-inferior axis was significantly correlated with the DVB (adjusted R2= 0.49, p= 0.0005). Among 8 patients with cervical tumor invading less than onehalf of the uterus, the target displacement affected by DVB was well-described by linear regression (adjusted R2= 0.61, p= 0.0008). For those with bulky tumor extent, the correlation between target displacement and DVB was much less apparent. For patients have anteverted uterus (n= 11), the DVB was associated with cervix-uterus motion on superior-inferior axis (adjusted R2 =0.40, p= 0.022), while for those with retroverted or tip-up uterus, there was no significant correlation. After a multivariate linear regression analysis, DVB and tumor extent were significantly correlated with uterus-cervix motion. Conclusion: The maximized bladder filling change (DVB), and tumor extent, were significantly correlated with uterus-cervix centroid displacement on the superiorinferior axis of cervical cancer patients.
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Publisher
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Type
journal article