Neoadjuvant chemoradiotherapy has become the standard treatment for locally advanced rectal cancer. Neoadjuvant chemoradiotherapy not only can reduce tumor size and recurrence, but also increase the tumor resection rate and anus retention rate with very slight side effect. Comparing with preoperative chemotherapy, preoperative chemoradiotherapy can further reduce the local recurrence rate and downstage. Middle and low rectal cancers can benefit more from neoadjuvant chemradiotherapy than high rectal cancer. It needs to refine the selection of appropriate patients and irradiation modes for neoadjuvant chemoradiotherapy. Different therapeutic reactions to neoadjuvant chemoradiotherapy affect the type of surgical techniques, hence calling for the need of much attention. Furthermore, many problems such as accurate staging before surgery, selection of suitable neoadjuvant chemoradiotherapy method, and sensitivity prediction to preoperative radiotherapy need to be well settled.

/pdf/a-review-of-neoadjuvant-chemoradiotherapy-for-locally-1345icbp38.pdf

A Review of Neoadjuvant Chemoradiotherapy for Locally Advanced Rectal Cancer

Growing genetic and molecular biological evidence suggests that the disruption of balance between Secreted Frizzled-Related Protein-1 (SFRP1) and β-catenin plays an important role in the initiation and development of multiple cancers. The aim of this study was to examine whether the expression of SFRP1 and β-catenin is associated with the clinical-pathologic features of patients with prostate cancer (PCa), and to evaluate their potential roles as predictive and prognostic biomarkers. In this study, a total of 61 patients with PCa and 10 patients with benign prostatic hyperplasia were included, and we showed that the expression of SFRP1 and β-catenin was correlated with the Gleason score, survival rate and response for endocrine therapy of PCa. The survival rates of PCa patients with low SFRP1 expression (P = 0.016) or high β-catenin expression (P = 0.004) were significantly poorer. A negative correlation (r = -0.275, P = 0.032) between SFRP1 and β-catenin was observed by Chi-square test. Multivariate analysis suggested that SFRP1 (hazard ratio, 0.429; 95% confidence intervals, 0.227–0.812; P = 0.009) may serve as an independent predictive and prognostic factor for PCa. We also showed that the protein and mRNA levels of SFRP1 in androgen-dependent PCa cell line LNCaP were significantly higher than those in androgen-independent PCa cell lines DU145 and PC3. However, the protein level of β-catenin in LNCaP cells was significantly lower than that in DU145 and PC3 cells, and no significant difference of β-catenin mRNA level was observed in LNCaP, DU145 and PC3 cells. Bisulfite sequencing PCR assay revealed significantly lower methylation level of SFRP1 promoter in LNCaP cells than that in DU145 and PC3 cells. Taken together, these findings suggest that SFRP1, which expression inversely correlates with that of β-catenin, is a favorable predictive and prognostic biomarker.

/pdf/diagnostic-value-of-sfrp1-as-a-favorable-predictive-and-376y02m8u4.pdf

Diagnostic value of SFRP1 as a favorable predictive and prognostic biomarker in patients with prostate cancer.

Image-guided radiotherapy (IGRT) enables optimal tumor targeting and sparing of organs-at-risk, which ultimately results in improved outcomes for patients. Magnetic resonance imaging (MRI) revolutionized diagnostic imaging with its superior soft tissue contrast, high spatiotemporal resolution, and freedom from ionizing radiation exposure. Over the past few years there has been burgeoning interest in MR-guided radiotherapy (MRgRT) to overcome current challenges in X-ray-based IGRT, including but not limited to, suboptimal soft tissue contrast, lack of efficient daily adaptation, and incremental exposure to ionizing radiation. In this review, we present an overview of the technologic advancements in IGRT that led to MRI-linear accelerator (MRL) integration. Our report is organized in three parts: (1) a historical timeline tracing the origins of radiotherapy and evolution of IGRT, (2) currently available MRL technology, and (3) future directions and aspirations for MRL applications.

https://www.mdpi.com/2077-0383/11/16/4730/pdf?version=1661333862

History of Technological Advancements towards MR-Linac: The Future of Image-Guided Radiotherapy

The aim of this study was to evaluate and compare the performance of intensity modulated radiation therapy (IMRT) plans, planned for low-field strength magnetic resonance (MR) guided linear accelerator (linac) delivery (labelled IMRT MRL plans), and clinical conventional volumetric modulated arc therapy (VMAT) plans, for the treatment of prostate cancer (PCa). Both plans used the original planning target volume (PTV) margins. Additionally, the potential dosimetric benefits of MR-guidance were estimated, by creating IMRT MRL plans using smaller PTV margins. 20 PCa patients previously treated with conventional VMAT were considered. For each patient, two different IMRT MRL plans using the low-field MR-linac treatment planning system were created: one with original (orig.) PTV margins and the other with reduced (red.) PTV margins. Dose indices related to target coverage, as well as dose-volume histogram (DVH) parameters for the target and organs at risk (OAR) were compared. Additionally, the estimated treatment delivery times and the number of monitor units (MU) of each plan were evaluated. The dose distribution in the high dose region and the target volume DVH parameters (D98%, D50%, D2% and V95%) were similar for all three types of treatment plans, with deviations below 1% in most cases. Both IMRT MRL plans (orig. and red. PTV margins) showed similar homogeneity indices (HI), however worse values for the conformity index (CI) were also found when compared to VMAT. The IMRT MRL plans showed similar OAR sparing when the orig. PTV margins were used but a significantly better sparing was feasible when red. PTV margins were applied. Higher number of MU and longer predicted treatment delivery times were seen for both IMRT MRL plans. A comparable plan quality between VMAT and IMRT MRL plans was achieved, when applying the same PTV margin. However, online MR-guided adaptive radiotherapy allows for a reduction of PTV margins. With a red. PTV margin, better sparing of the surrounding tissues can be achieved, while maintaining adequate target coverage. Nonetheless, longer treatment delivery times, characteristic for the IMRT technique, have to be expected.

/pdf/dosimetric-comparison-of-mr-linac-based-imrt-and-4kxo2cjj7r.pdf

Dosimetric comparison of MR-linac-based IMRT and conventional VMAT treatment plans for prostate cancer

THIS STUDY WAS PERFORMED TO EVALUATE DOSIMETRIC DIFFERENCES BETWEEN CURRENT INTENSITY MODULATED RADIATION THERAPY (IMRT) DELIVERY MODES: Step-and-shoot (SS), sliding window (SW), and volumetric modulated arc therapy (VMAT). Plans for 15 prostate cancer patients with 10 MV photon beams using each IMRT mode were generated. Patients had three planning target volumes (PTVs) including prostate, prostate plus seminal vesicles, and pelvic lymphatics. Dose volume histograms (DVHs) of PTVs and organs at risk (OARs), tumor control probability (TCP) and normal tissue complication probabilities (NTCPs), conformation number, and monitor units (MUs) used were compared. Statistical analysis was performed using the analysis of variance (ANOVA) technique. The TCPs were 0.99). Doses to all critical structures were higher on average with SW method compared to SS, but insignificant. NTCP values were lowest for VMAT in all structures excepting bladder. Normal tissue volumes receiving doses in the 20-30 Gy range were reduced for VMAT compared to SS. Percentage of MUs required for VMAT to deliver a comparable plan to SS and SW was at least 40% less. In conclusion, similar target coverage and normal tissue doses were found by the three compared modes and the dosimetric differences were small.

Dosimetric comparison between IMRT delivery modes: Step-and-shoot, sliding window, and volumetric modulated arc therapy - for whole pelvis radiation therapy of intermediate-to-high risk prostate adenocarcinoma

Comparison of doses received by the hippocampus in patients treated with single isocenter– vs multiple isocenter–based stereotactic radiation therapy to the brain for multiple brain metastases

This study aims to evaluate treatment plans generated by Step-and-Shoot (SS), Sliding Window (SW) and Volumetric Modulated Arc Therapy (VMAT) in order to assess the differences in dose volume histograms of planning target volume (PTV) and organs at risk (OAR), conformity indices, radiobiological evaluations, and plan quality for prostate cancer cases. Six prostate cancer patients treated in our center were selected for this retrospective study. Treatment plans were generated with Eclipse version 8.9 using 10 MV photon beams. For VMAT, Varian Rapid Arc with 1 or 2 arcs, and for SS and SW IMRT, 7-9 fields were used. Each plan had three PTVs with prescription doses of 81, 59.4, and 45 Gy to prostate, to prostate and lymph nodes, and to pelvis, respectively. Doses to PTV and OAR and the conformal indices (COIN) were compared among three techniques. The equivalent uniform dose (EUD), tumor control probability (TCP) and normal tissue complication probability (NTCP) were calculated and compared. The mean doses to the PTV prostate on average were 83 Gy and the percent differences of mean dose among all techniques were below 0.28. For bladder and rectum, the percent differences of mean dose among all techniques were below 2.2. The COIN did not favour any particular delivery method over the other. The TCP was higher with SS and SW for four patients and higher with VMAT for two patients. The NTCP for the rectum was the lowest with VMAT in five out of the six patients. The results show similar target coverage in general.

Dosimetric comparison of volumetric modulated Arc therapy, step-and-shoot, and sliding window IMRT for prostate cancer

Purpose: To compare quality of single and multiple isocenter stereotactic IMRT treatment plans for multiple intracranial targets. Methods: Five patients (two with three and three with two brain metastatic tumors) treated with multiple isocenters using 9 to 12 non‐coplanar beams per lesion were replanned for single isocenter 10 to 12 non‐coplanar beams. Identical contour sets and dose‐volume constraints were applied. Plans were developed using BrainLab iPlan system for delivery with Varian TrueBeam STx machine. The prescribed dose to each target was 25 Gy in five fractions and minimum 95% dose was required to cover > 95% of target volume. Results: All plans satisfied the dose‐volume constraints, with no significant differences in dose conformity between single and multiple isocenter plans. The mean Paddick conformity index (CI) for two target single and multiple isocenter plans was 0.76 and 0.75 (p = 0.93), and for three target single and multiple isocenter plans was 0.73 and 0.70 (p = 0.37), respectively. Normal brain tissue doses were higher for single isocenter plans compared to multiple isocenter plans. The average normal brain volumes receiving 15 and 10 Gy for two target plans (single vs. multiple isocenter) were: (4.8% vs. 2.1%) and (8.9% vs. 4.5%), respectively. For three target plans these volumes were: (2.0% vs. 1.5%) and (4.6% vs. 3.4%). The estimated total treatment time (patient set‐up, imaging‐verification, beam‐on time at 600 MU/min, etc.) were approximately 1.75 and 2.5 times lower with two and three target single isocenter delivery, respectively. Conclusion: Single isocenter plans were capable of producing quality treatment plans similar to multiple isocenter plans. Treatment delivery times were much higher and the normal brain tissue doses were only slightly lower at 10 and 15 Gy dose levels for multiple isocenter plans compared to single isocenter plans. Clinical consequences of these normal tissue doses are however unknown.

SU‐E‐T‐672: Comparisons of Single and Multiple Isocenter Stereotactic IMRT Treatment Planning for Multiple Brain Metastases Treatment

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Dosimetric comparison between IMRT delivery modes: Step-and-shoot, sliding window, and volumetric modulated arc therapy - for whole pelvis radiation therapy of intermediate-to-high risk prostate adenocarcinoma

Comparison of doses received by the hippocampus in patients treated with single isocenter– vs multiple isocenter–based stereotactic radiation therapy to the brain for multiple brain metastases

Dosimetric comparison of volumetric modulated Arc therapy, step-and-shoot, and sliding window IMRT for prostate cancer

SU‐E‐T‐672: Comparisons of Single and Multiple Isocenter Stereotactic IMRT Treatment Planning for Multiple Brain Metastases Treatment