The effect of lower urinary tract substructure doses on side effects of cervical cancer image-guided adaptive brachytherapy.

OBJECTIVE: Image-Guided Adaptive Brachytherapy (IGABT) provides a survival advantage in locally advanced cervical cancer (LACC). Although side effects are seen less with this technique, dose parameters that cause urinary side effects are still questionable. We aim to investigate whether the radiotherapy doses of the lower urinary tract substructures (LUSS) affect the urinary system side effects (USSE) of cervical cancer external beam radiotherapy (EBRT) and the IGABT. METHODS: LUSS (bladder, trigone, bladder neck, and urethra) doses were calculated in 40 patients diagnosed with LACC and receiving primary EBRT, IGABT, and concomitant chemotherapy. D0.1cc, D2cc, and D50% values were examined by contouring the bladder, trigone, bladder neck, and urethra from the intracavitary BT planning computed tomography (CT) images taken every 4 BT fractions, retrospectively. Besides, late USSE (urgency, dysuria (recurrent), frequency, obstruction, incontinence, hematuria, fistula, cystitis) were queried and categorized according to Common Toxicity Criteria for Adverse Events version 5.0. STATISTICAL ANALYSIS USED: The Chi-square and Fisher's exact tests, Mann-Whitney U-test. RESULTS: For the whole study population, for both incontinence and dysuria, trigone (D50%), urethra (D50%, D0.1cc,), and bladder neck (D50%, D0.1cc, D2cc) volume and hot spot doses remained significant. For cystitis, urethra (D50%, D0.1cc,) and bladder neck doses (D0.1cc, D50%, D2cc) are worth investigating. CONCLUSIONS: Although USSE is less common in the intensity-modulated radiation therapy and IGABT era, it may be meaningful to take the doses of LUSS into account when planning IGABT. In addition, delineation of LUSS using only CT seems feasible. More proof is needed to determine delineation technique and dose constraints for LUSS for IGABT.

Evaluation of the voluntary deep inspiration breath-hold reproducibility in left-sided breast radiotherapy.

PURPOSE: Voluntary deep inspiration breath hold (v-DIBH) reduces cardiac dose during left-sided breast irradiation. The purpose of this study is to evaluate the reproducibility and variability of breath-hold level (BHL) using breath-hold curves and lateral kV setup images together. MATERIAL/METHOD: A retrospective analysis of 30 left breast cancer patients treated using the v-DIBH technique in our department is performed. The BHL difference is measured from breath hold curves and lateral (LAT) kilo-Voltage (kV) setup images. The planning CT image and the selected treatment fraction data are collected. If the changes in BHL relate to the displacement of various bones in the kV setup, images are assessed. Furthermore, the maximum heart distance inside the treatment field is compared from LAT MV portal images. RESULTS: The median and mean values of the BHL are nearly identical in different fractions (good reproducibility). However, the mean BHL values between planning and all measured fractions are statistically different; 16.3 vs. 20.8 mm for the planning and measured fractions (p < 0.001), which indicates that the variability of BHL is significantly different. CONCLUSION: While reproducibility testing shows good agreement for inter-fractional breath-hold level, the variability between planning and fractions is relatively poor.