Effectiveness of rectal displacement devices in managing prostate motion: a systematic review.

PURPOSE: To determine whether rectal displacement devices (RDDs) have a prostate-stabilizing effect during prostate external beam radiotherapy (EBRT). METHODS: A systematic literature search using the PubMed database from January 1, 2000 to December 30th, 2019 was conducted. The effect of RDDs on inter- and intra-fractional prostate displacements was extracted. RESULTS: From 356 articles identified via the PubMed database and hand search, 21 articles were included in the systematic review. There was no randomized study. Twelve studies evaluated the role of the endorectal balloon (ERB) in managing prostate motion. Four studies reported the effect of hydrogel spacer on prostate motion. Four studies examined the effect of the rectal retractor (RR) on intra-fractional prostate motion, and only one study assessed the impact of ProSpare (Nottinghamshire, UK) in reducing prostate motion. CONCLUSION: Using an ERB significantly reduces intra-fractional prostate motion. This prostate-stabilizing effect of the ERB can translate into reduced planning target volume (PTV) margins and additional rectal dose sparing. Even with an ERB in place, inter-fractional prostate displacements are seen. As a consequence, ERB application does not obviate daily verification; however, this is not a crucial topic because pretreatment imaging is always done nowadays. As compared with ERB, the hydrogel spacer significantly reduces rectal dose and toxicity without influencing prostate immobilization. The RR can increase prostate and rectal inter- and intra-fractional stability without a clear influence on the reduction of rectal toxicity. Finally, it is unclear whether ProSpare is a suitable device reducing prostate motion. Further study will be required to clarify whether the prostate-stabilizing effects of the ERB and RR can result in a safe reduction of PTV margins and further sparing of organs at risks, especially the rectum.

Assessment of background radiation levels in the southeast of Iran.

Background: Measuring background radiation (BR) is highly important from different perspectives, especially from that of human health. This study was conducted to measure BR in the southeast of Iran. Methods: BR was measured in Hormozgan and Sistan-Bluchestan provinces using portable Environmental Radiation Meter Type 6- 80 detector. The average value was used to calculate the absorbed dose rate and indoor annual effective dose (AED) from BR. In addition, excess lifetime cancer risk (ELCR) was evaluated. Results: The results showed that the maximum and minimum absorbed dose rates were 71.9 and 34.2 nGy.h-1 in Abomoosa and Minab in Hormozgan province and 90.0 and 47.8 nGy.h-1 in Zahedan and Chabahar in Sistan-Bluchestan province, respectively. Data indicated that these areas had a lower BR level compared with the worldwide level. The ELCR from indoor AED was larger compared with the worldwide average of 0.29 × 10-3. Conclusion: This study provided a reference for designing and developing specific regional surveys associated with the measurement of natural BR in the southeast of Iran.

In regard to Cuccia et al.: impact of hydrogel peri-rectal spacer insertion on prostate gland intra-fraction motion during 1.5 T MR-guided stereotactic body radiotherapy.

We read the article entitled "Impact of hydrogel peri-rectal spacer insertion on prostate gland intra-fraction motion during 1.5 T MR-guided stereotactic body radiotherapy" with great interest. In that study, the author reported that there is a statistically significant difference in the rotational antero-posterior shifts between the spacer and the non-spacer groups. Also, there was no statistically significant difference between the groups in terms of translational shifts. However, there are some points about the study. In this letter, we aimed to clarify these points.

Fiducial markers in prostate cancer image-guided radiotherapy.

Background: Image-guided radiotherapy (IGRT) is recommended to reduce the risk of geometrical miss when modern radiotherapy technologies with high grades of conformity are used. The purpose of this study was to evaluate the efficacy of fiducial markers (FMs) for electronic portal imaging in prostate cancer radiotherapy in term of evaluating the complications associated with FMs implantation, quantifying inter-fraction prostate motion, and determination of optimal planning target volume (PTV) margins. Methods: In this single institution, prospective, consecutive study, 27 patients underwent implantation of three-gold seed FMs into the prostate gland before prostate radiotherapy. Prior to computed tomography planning, all patients were asked to report any complication associated with FMs implantation that have experienced to date. Daily pre-treatment electronic portal images were captured, and prostate position errors were corrected if they were greater than 2 mm along three translational directions. Optimal PTV expansions were computed using van Herk formula [PTV-margin= 2.5Σ + 0.7σ]. Results: FMs implantation was successful with an acceptable toxicity profile in all patients. Without IGRT, margins of 5.4 mm, 5.8 mm and 5.5 mm, in vertical, longitudinal and lateral directions, respectively, are needed for a 95% confidence level of complete clinical target volume (CTV) coverage in each treatment session. The PTV margins of 3.0 mm, 3.3 mm and 4.0 mm in corresponding directions were calculated when FMs based electronic portal imaging was applied. Conclusion: FMs based electronic portal imaging is an effective tool for prostate cancer IGRT.