Prospective comparison of rectal dose reduction during intracavitary brachytherapy for cervical cancer using three rectal retraction techniques.

PURPOSE: To compare three rectal retraction methods on dose to organs at risk, focusing on rectal dose, in cervix cancer patients treated with high-dose-rate intracavitary brachytherapy. METHODS AND MATERIALS: A prospective study was conducted on patients with cervical carcinoma treated with chemoradiotherapy, including external beam radiation and four fractions of high-dose-rate intracavitary brachytherapy prescribed to Point A using a ring and tandem applicator under conscious sedation. Rectal retraction methods included: a rectal retractor blade (RR), vaginal gauze packing (VP), and a tandem Foley balloon (FB). All three methods were used in all patients. The RR was used first, and the following applications were randomly assigned to VP or FB. CT planning was used to calculate D2cc for rectum, sigmoid, small bowel, and bladder. The Wilcoxon signed rank test was used to determine if the median dose differences between methods were statistically significant. RESULTS: In these 11 patients, median dose (min, max) in cGy to the rectum using RR, FB, and VP was 131 (102, 165), 199 (124, 243), and 218 (149, 299), respectively. The RR demonstrated lower median intrapatient doses to rectum compared with FB and VP (-55 cGy; p = 0.014 and -76 cGy; p = 0.004, respectively). The RR also resulted in lower sigmoid doses. No differences in dose were observed between the VP and FB methods. CONCLUSION: The rectal retractor significantly reduced the dose to rectum and sigmoid compared with FP and VP. In patients treated under conscious sedation, the RR method provides the best rectal sparing. There were no significant differences in dose observed between the FB and VP techniques

Assessing patient characteristics and radiation-induced non-targeted effects in vivo for high dose-rate (HDR) brachytherapy

<div><p><i>Purpose</i>: To test whether blood, urine, and tissue based colony-forming assays are a useful clinical detection tool for assessing fractionated treatment responses and non-targeted radiation effects in bystander cells.</p><p><i>Materials and methods</i>: To assess patients’ responses to radiation treatments, blood serum, urine, and an esophagus explant-based in vivo colony-forming assay were used from oesophageal carcinoma patients. These patients underwent three fractions of high dose rate (HDR) intraluminal brachytherapy (ILBT).</p><p><i>Results</i>: Human keratinocyte reporters exposed to blood sera taken after the third fraction of brachytherapy had a significant increase in cloning efficiency compared to baseline samples (<i>p</i> < 0.001). Such results may suggest an induced radioresistance response in bystander cells. The data also revealed a clear inverse dose-rate effect during late treatment fractions for the blood sera data only. Patient characteristics such as gender had no statistically significant effect (<i>p</i> > 0.05). Large variability was observed among the patients’ tissue samples, these colony-forming assays showed no significant changes throughout fractionated brachytherapy (<i>p</i> > 0.05).</p><p><i>Conclusion</i>: Large inter-patient variability was found in the urine and tissue based assays, so these techniques were discontinued. However, the simple blood-based assay had much less variability. This technique may have future applications as a biological dosimeter to predict treatment outcome and assess non-targeted radiation effects.</p></div