Radiomics based predictive modeling of rectal toxicity in prostate cancer patients undergoing radiotherapy: CT and MRI comparison

BACKGROUND

Rectal toxicity is one of the common side effects after radiotherapy in prostate cancer patients. Radiomics is a non-invasive and low-cost method for developing models of predicting radiation toxicity that does not have the limitations of previous methods. These models have been developed using individual patients' information and have reliable and acceptable performance. This study was conducted by evaluating the radiomic features of computed tomography (CT) and magnetic resonance (MR) images and using machine learning (ML) methods to predict radiation-induced rectal toxicity.

METHODS

Seventy men with pathologically confirmed prostate cancer, eligible for three-dimensional radiation therapy (3DCRT) participated in this prospective trial. Rectal wall CT and MR images were used to extract first-order, shape-based, and textural features. The least absolute shrinkage and selection operator (LASSO) was used for feature selection. Classifiers such as Random Forest (RF), Decision Tree (DT), Logistic Regression (LR), and K-Nearest Neighbors (KNN) were used to create models based on radiomic, dosimetric, and clinical data alone or in combination. The area under the curve (AUC) of the receiver operating characteristic curve (ROC), accuracy, sensitivity, and specificity were used to assess each model's performance.

RESULTS

The best outcomes were achieved by the radiomic features of MR images in conjunction with clinical and dosimetric data, with a mean of AUC: 0.79, accuracy: 77.75%, specificity: 82.15%, and sensitivity: 67%.

CONCLUSIONS

This research showed that as radiomic signatures for predicting radiation-induced rectal toxicity, MR images outperform CT images.

Hyaluronic acid spacer in prostate cancer radiotherapy: dosimetric effects, spacer stability and long-term toxicity and PRO in a phase II study

BACKGROUND

Perirectal spacers may be beneficial to reduce rectal side effects from radiotherapy (RT). Here, we present the impact of a hyaluronic acid (HA) perirectal spacer on rectal dose as well as spacer stability, long-term gastrointestinal (GI) and genitourinary (GU) toxicity and patient-reported outcome (PRO).

METHODS

In this phase II study 81 patients with low- and intermediate-risk prostate cancer received transrectal injections with HA before external beam RT (78 Gy in 39 fractions). The HA spacer was evaluated with MRI four times; before (MR0) and after HA-injection (MR1), at the middle (MR2) and at the end (MR3) of RT. GI and GU toxicity was assessed by physician for up to five years according to the RTOG scale. PROs were collected using the Swedish National Prostate Cancer Registry and Prostate cancer symptom scale questionnaires.

RESULTS

There was a significant reduction in rectal V70% (54.6 Gy) and V90% (70.2 Gy) between MR0 and MR1, as well as between MR0 to MR2 and MR3. From MR1 to MR2/MR3, HA thickness decreased with 28%/32% and CTV-rectum space with 19%/17% in the middle level. The cumulative late grade ≥ 2 GI toxicity at 5 years was 5% and the proportion of PRO moderate or severe overall bowel problems at 5 years follow-up was 12%. Cumulative late grade ≥ 2 GU toxicity at 5 years was 12% and moderate or severe overall urinary problems at 5 years were 10%.

CONCLUSION

We show that the HA spacer reduced rectal dose and long-term toxicity.

Radiotherapy-related toxicity for localized prostate cancer: meta-analysis comparing conventional or moderately hypofractionated vs. ultrahypofractionated protocols

BACKGROUND

To compare toxicities in relation to standard radiation treatments [conventional fractionation RT (CRT) and moderate hypofractionated RT (MRT)] with ultrahypofractionated RT (URT) in the treatment of patients with localized PCa.

METHODS

A searched was performed in Medline, Embase, Cochrane CENTRAL, and LILACS to January 2020 for studies comparing URT to CRT and/or MRT in relation to genitourinary (GU) and gastrointestinal (GI) toxicity in the treatment of patients with localized PCa. URT, MRT and CRT were defined as protocols delivering a daily dose of ≥5 Gy, 2.4-4.9 Gy, and <2.4 Gy per fractions regardless total dose, respectively.

RESULTS

Eight studies with 2929 patients with localized PCa were included in the analysis. These eight studies did not find any difference between URT and MRT/CRT groups in relation to acute GU toxicity (21.0% × 23.8%, RD -0.04; 95% CI -0.13, 0.06; p = 0.46; I² = 89%) and acute GI toxicity (4.9% × 6.9%, RD -0.03; 95% CI -0.07, 0.01; p = 0.21; I² = 79%). Six studies did not find any difference between URT and MRT/CRT groups in relation to late GU toxicity (3.9% × 4.7%, RD -0.01; 95% CI -0.03, 0.00; p = 0.16; I² = 19%) and late GI toxicity (2.1% × 3.5%, RD -0.01; 95% CI -0.03, 0.00; p = 0.05; I² = 22%).

CONCLUSION

The present study suggests that acute GU/GI and late GU/GI toxicity are similar between URT and standard protocols. More studies with longer follow-ups directed to oncology outcomes are warranted before any recommendation on this topic.

Clinical effects of rectal retractor application in prostate cancer radiotherapy

Background: Radiation-induced rectal toxicities remain as a major risk during prostate radiotherapy. One approach to the reduction of rectal radiation dose is to physically increase the distance between the rectal wall and prostate. Therefore, the aim of this study was to evaluate whether the application of the rectal retractor (RR) can reduce rectal dose and toxicity in prostate cancer 3-dimensional conformal radiotherapy (3D-CRT).

Methods: Overall, 36 patients with localized prostate cancer were randomized into the 2 groups, 18 patients with RR in-place and 18 without RR. All patients underwent planning computed tomography (CT). Patients were treated with 70 Gy in 35 fractions of 3D-CRT. In the RR group, RR was used during cone-down 20 treatment fractions. Acute and late gastrointestinal (GI) toxicities were assessed using EORTC/RTOG scoring system weekly during radiotherapy, 3, and 12 months after treatment. Device-related events were recorded according to CTCAE version 4.0. Patient characteristics, cancer differences, and dosimetric data for the RR and non-RR groups were compared using a Man-Whitney U test for continuous variables, and Fisher exact test for categorical data. The EORTC/RTOG scores for the 2 groups were compared using Fisher exact test. A P value <0.05 was considered statistically significant.

Results: A RR significantly reduced mean dose (Dmean) to the rectum as well as rectal volume receiving 50% to 95% (V50-95%) of prescribed dose. The absolute reduction of rectal Dmean was 10.3 Gy. There was no statistically significant difference in acute GI toxicity between groups during treatment or at 3 months. At 12 months, 2 patients in the RR group and 9 in the control group experienced late grade ≥ 1 GI toxicity (p=0.027). No patients in the RR group reported late grade ≥ 2 GI toxicity, whereas 3 patients in the control group experienced late grade 2 GI toxicity. In the RR group, 6 patients reported grade 1 rectal discomfort and pain according to CTCAE version 4.0.

Conclusion: The application of the RR showed a significant rectum sparing effect, resulting in substantially reducing late GI toxicity.

Associations between voxel-level accumulated dose and rectal toxicity in prostate radiotherapy

Background and Purpose

Associations between dose and rectal toxicity in prostate radiotherapy are generally poorly understood. Evaluating spatial dose distributions to the rectal wall (RW) may lead to improvements in dose-toxicity modelling by incorporating geometric information, masked by dose-volume histograms. Furthermore, predictive power may be strengthened by incorporating the effects of interfraction motion into delivered dose calculations.Here we interrogate 3D dose distributions for patients with and without toxicity to identify rectal subregions at risk (SRR), and compare the discriminatory ability of planned and delivered dose.

Material and Methods

Daily delivered dose to the rectum was calculated using image guidance scans, and accumulated at the voxel level using biomechanical finite element modelling. SRRs were statistically determined for rectal bleeding, proctitis, faecal incontinence and stool frequency from a training set (n = 139), and tested on a validation set (n = 47).

Results

SRR patterns differed per endpoint. Analysing dose to SRRs improved discriminative ability with respect to the full RW for three of four endpoints. Training set AUC and OR analysis produced stronger toxicity associations from accumulated dose than planned dose. For rectal bleeding in particular, accumulated dose to the SRR (AUC 0.76) improved upon dose-toxicity associations derived from planned dose to the RW (AUC 0.63). However, validation results could not be considered significant.

Conclusions

Voxel-level analysis of dose to the RW revealed SRRs associated with rectal toxicity, suggesting non-homogeneous intra-organ radiosensitivity. Incorporating spatial features of accumulated delivered dose improved dose-toxicity associations. This may be an important tool for adaptive radiotherapy in the future.

Rates of rectal toxicity in patients treated with high dose rate brachytherapy as monotherapy compared to dose-escalated external beam radiation therapy for localized prostate cancer

BACKGROUND

Using a prospectively collected institutional database, we compared rectal toxicity following high dose rate (HDR) brachytherapy as monotherapy relative to dose-escalated external beam radiotherapy (EBRT) for patients with localized prostate cancer.

METHODS

2683 patients treated with HDR or EBRT between 1994 and 2017 were included. HDR fractionation was 38 Gy/4 fractions (n = 321), 24 Gy/2 (n = 96), or 27 Gy/2 (n = 128). EBRT patients received a median dose of 75.6 Gy in 1.8 Gy fractions [range 70.2-82.8 Gy], using either 3D conformal or intensity modulated radiotherapy (IMRT). EBRT patients underwent 3D image guidance via an off-line adaptive process.

RESULTS

Median follow-up was 7.5 years (7.4 years for EBRT and 7.9 years for HDR). 545 patients (20.3%) received HDR brachytherapy and 2138 (79.7%) EBRT. 69.1% of EBRT patients received IMRT. Compared to EBRT, HDR was associated with decreased rates of acute grade ≥2 diarrhea (0.7% vs. 4.5%, p < 0.001), rectal pain/tenesmus (0.6% vs. 7.9%, p < 0.001), and rectal bleeding (0% vs. 1.6%, p = 0.001). Rates of chronic grade ≥2 rectal bleeding (1.3% vs. 8.7%, p < 0.001) and radiation proctitis (0.9% vs. 3.3%, p = 0.001) favored HDR over EBRT. Rates of any chronic rectal toxicity grade ≥2 were 2.4% vs. 10.5% (p < 0.001) for HDR versus EBRT, respectively. In those treated with IMRT, acute and chronic rates of any grade ≥2 GI toxicity were significantly reduced but remained significantly greater than those treated with HDR.

CONCLUSIONS

In appropriately selected patients with localized prostate cancer undergoing radiation therapy, HDR brachytherapy as monotherapy is an effective strategy for reducing rectal toxicity.

Case series illustrating the synergistic use of hydrogel spacer and MR-guidance to increase the radiotherapeutic index for localized prostate cancer

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Polyethylene glycol hydrogel spacer allows radiotherapy in challenging scenarios.

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Polyethylene glycol hydrogel material properties may limit broader applicability.

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MRI-guided brachytherapy unique scenario to use PEG without compromising prostate resolution.

Background

The risk of gastrointestinal (GI) toxicity may limit the use of curative-intent radical radiotherapy (RT) for prostate cancer (PCa) in circumstances where morbidity of treatment may exceed an acceptable threshold. Rectal spacers are used to expand the distance between the anterior rectal wall and the prostate, consequently sparing the rectum from the high-dose region.

Case presentations

We report three clinical scenarios of PCa patients treated at our institution, where risk of RT-associated rectal toxicity may be increased: inflammatory bowel disease (IBD), salvage brachytherapy (BT) after previous external beam RT (EBRT), and tailored dose-escalation with focal BT to the gross tumor volume followed by stereotactic body RT. Prior to RT, a polyethylene glycol (PEG) hydrogel spacer was successfully placed in all cases. Treatment comprised magnetic resonance (MR) guided high dose-rate BT ± EBRT. All patients completed treatment uneventfully, without any significant GI toxicity at last follow-up.

Conclusions

These cases illustrate the utility of PEG hydrogel spacer, where concerns of radiation induced toxicity may have previously limited the application of radiotherapy. The synergistic use of these novel devices together with MR-guided BT may expand the indications and therapeutic index of curative-intent RT-based treatments, while minimizing the risks of GI toxicity.

Stereotactic body radiotherapy with periprostatic hydrogel spacer for localized prostate cancer: toxicity profile and early oncologic outcomes

Background

Multiple phase I-II clinical trials have reported on the efficacy and safety of prostate stereotactic body radiotherapy (SBRT) for the treatment of prostate cancer. However, few have reported outcomes for prostate SBRT using periprostatic hydrogel spacer (SpaceOAR; Augmenix). Herein, we report safety and efficacy outcomes from our institutional prostate SBRT experience with SpaceOAR placement.

Methods

Fifty men with low- or intermediate-risk prostate cancer treated at a single institution with linear accelerator-based SBRT to 3625 cGy in 5 fractions, with or without androgen deprivation therapy (ADT) were included. All patients underwent SpaceOAR and fiducial marker placement followed by pre-treatment MRI. Toxicity assessments were conducted at least weekly while on treatment, 1 month after treatment, and every follow-up visit thereafter. Post-treatment PSA measurements were obtained 4 months after SBRT, followed by every 3–6 months thereafter. Acute toxicity was documented per RTOG criteria.

Results

Median follow up time was 20 (range 4–44) months. Median PSA at time of diagnosis was 7.4 (2.7–19.5) ng/ml. Eighteen men received 6 months of ADT for unfavorable intermediate risk disease. No PSA failures were recorded. Median PSA was 0.9 ng/mL at 20 months; 0.08 and 1.32 ng/mL in men who did and did not receive ADT, respectively. Mean prostate-rectum separation achieved with SpaceOAR was 9.6 ± 4 mm at the prostate midgland.

No grade ≥ 3 GU or GI toxicity was recorded. During treatment, 30% of men developed new grade 2 GU toxicity (urgency or dysuria). These symptoms were present in 30% of men at 1 month and in 12% of men at 1 year post-treatment. During treatment, GI toxicity was limited to grade 1 symptoms (16%), although 4% of men developed grade 2 symptoms during the first 4 weeks after SBRT. All GI symptoms were resolving by the 1 month post-treatment assessment and no acute or late rectal toxicity was reported > 1 month after treatment.

Conclusions

Periprostatic hydrogel placement followed by prostate SBRT resulted in minimal GI toxicity, and favorable early oncologic outcomes. These results indicate that SBRT with periprostatic spacer is a well-tolerated, safe, and convenient treatment option for localized prostate cancer.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1346-5) contains supplementary material, which is available to authorized users.

Definitive, intensity modulated tomotherapy with a simultaneous integrated boost for prostate cancer patients - Long term data on toxicity and biochemical control

Aim

To report long-term data regarding biochemical control and late toxicity of simultaneous integrated boost intensity modulated radiotherapy (SIB-IMRT) with tomotherapy in patients with localized prostate cancer.

Background

Dose escalation improves cancer control after curative intended radiation therapy (RT) to patients with localized prostate cancer, without increasing toxicity, if IMRT is used.

Materials and methods

In this retrospective analysis, we evaluated long-term toxicity and biochemical control of the first 40 patients with intermediate risk prostate cancer receiving SIB-IMRT. Primary target volume (PTV) 1 including the prostate and proximal third of the seminal vesicles with safety margins was treated with 70 Gy in 35 fractions. PTV 2 containing the prostate with smaller safety margins was treated as SIB to a total dose of 76 Gy with 2.17 Gy per fraction. Toxicity was evaluated using an adapted CTCAE-Score (Version 3).

Results

Median follow-up of living patients was 66 (20-78) months. No late genitourinary toxicity higher than grade 2 has been reported. Grade 2 genitourinary toxicity rates decreased from 58% at the end of the treatment to 10% at 60 months. Late gastrointestinal (GI) toxicity was also moderate, though the prescribed PTV Dose of 76 Gy was accepted at the anterior rectal wall. 74% of patients reported any GI toxicity during follow up and no toxicity rates higher than grade 2 were observed. Grade 2 side effects were reported by 13% of the patients at 60 months. 5-year freedom from biochemical failure was 95% at our last follow up.

Conclusion

SIB-IMRT using daily MV-CT guidance showed excellent long-term biochemical control and low toxicity rates.

Rectal retractor application during image-guided dose-escalated prostate radiotherapy

PURPOSE

To investigate efficacy of a rectal retractor (RR) on rectal dose during image-guided dose-escalated prostate three-dimensional conformal radiotherapy (3DCRT).

PATIENTS AND METHODS

In all, 21 patients with localized prostate cancer were treated with a RR for 3DCRT in 40 × 2 Gy. Patient underwent two scans for radiotherapy planning, without and with RR. RR was used for the first half of the treatment sessions. Two plans were created for each patient to compare the effect of RR on rectal doses. PTW-31014 Pinpoint chamber embedded within RR was used for in vivo dosimetry in 6 of 21 patients. The patient tolerance and acute rectal toxicity were surveyed during radiotherapy using Common Terminology Criteria for Adverse Events (CTCAE) v.4.0.

RESULTS

Patients tolerated the RR well during 20 fractions with mild degree of anal irritation. Using a RR significantly reduced the rectal wall (RW), anterior RW and posterior RW dose-volume parameters. The average RW D_mean was 29.4 and 43.0 Gy for plans with and without RR, respectively. The mean discrepancy between the measured dose and planned dose was -3.8% (±4.9%). Grade 1 diarrhea, rectal urgency and proctitis occurred in 4, 2 and 3 cases, respectively. There were no grade ≥2 acute rectal toxicities during the treatment.

CONCLUSION

Rectal retraction resulted in a significant reduction of rectal doses with a safe toxicity profile, which may reduce rectal toxicity. Dosimeter inserted into the RR providing a practical method for in vivo dosimetric verification. Further prospective clinical studies will be necessary to demonstrate the clinical advantage of RR.

Modeling of Acute Rectal Toxicity to Compare Two Patient Positioning Methods for Prostate Cancer Radiotherapy: Can Toxicity Modeling be Used for Quality Assurance?

Purpose:

Intensity Modulated Radiation Therapy (IMRT) allows for significant dose reductions to organs at risk in prostate cancer patients. However, the accurate delivery of IMRT plans can be compromised by patient positioning errors. The purpose of this study was to determine if the modeling of grade ≥ 2 acute rectal toxicity could be used to monitor the quality of IMRT protocols.

Materials and Methods:

79 patients treated with Image and Fiducial Markers Guided IMRT (FMIGRT) and 302 patients treated with trans-abdominal ultrasound guided IMRT (USGRT) was selected for this study. Treatment plans were available for the FMIGRT group, and hand recorded dosimetric indices were available for both groups. We modeled toxicity in the FMIGRT group using the Lyman Kutcher Burman (LKB) and Univariate Logistic Regression (ULR) models, and we modeled toxicity in USGRT group using the ULR model. We performed Receiver Operating Characteristics (ROC) analysis on all of the models and compared the Area under the ROC curve (AUC) for the FMIGRT and the USGRT groups.

Results:

The observed Incidence of grade ≥ 2 rectal toxicity was 20% in FMIGRT patients and 54% in USGRT patients. LKB model parameters in the FMIGRT group were TD₅₀=56.8 Gy, slope m=0.093, and exponent n=0.131. The most predictive indices in the ULR model for the FMIGRT group were D_25% and V_{50 Gy}. AUC for both models in the FMIGRT group was similar (AUC=0.67). The FMIGRT URL model predicted less than a 37% incidence of grade ≥ 2 acute rectal toxicity in the USGRT group. A fit of the ULR model to USGRT data did not yield a predictive model (AUC=0.5).

Conclusion:

Modeling of acute rectal toxicity provided a quantitative measure of the correlation between planning dosimetry and this clinical endpoint. Our study suggests that an unusually weak correlation may indicate a persistent patient positioning error.

A novel model to correlate hydrogel spacer placement, perirectal space creation, and rectum dosimetry in prostate stereotactic body radiotherapy

BACKGROUND

The SpaceOAR hydrogel is employed to limit rectal radiation dose during prostate radiotherapy. We identified a novel parameter - the product of angle θ and hydrogel volume - to quantify hydrogel placement. This parameter predicted rectum dosimetry and acute rectal toxicity in prostate cancer patients treated with stereotactic body radiotherapy to 36.25 Gy in 5 fractions.

METHODS

Twenty men with low- and intermediate-risk prostate cancer underwent hydrogel placement from 2015 to 2017. Hydrogel symmetry was assessed on the CT simulation scan in 3 axial slices (midgland, 1 cm above midgland, 1 cm below midgland). Two novel parameters quantifying hydrogel placement - hydrogel volume and angle θ formed by the prostate, hydrogel, and rectum - were measured, and the normalized product of θ and hydrogel volume calculated. These were then correlated with perirectal distance, rectum maximum 1-3 cc point doses (rD_max 1-3 cc), and rectum volumes receiving 80-95% of the prescription dose (rV80-95%). Acute rectal toxicity was recorded per RTOG criteria.

RESULTS

In 50% of patients, hydrogel placement was symmetric bilaterally to within 1 cm of midline in all three CT simulation scan axial slices. Lateral hydrogel asymmetry < 2 cm in any one axial slice did not affect rectum dosimetry, but absence of hydrogel in the inferior axial slice resulted in a mean increase of 171 cGy in the rD_max 1 cc (p < 0.005). The perirectal distance measured at prostate midgland, midline (mean 9.1 ± 4.3 mm) correlated strongly with rV95 (R² 0.6, p < 0.001). The mean hydrogel volume and θ were 10.3 ± 4.5 cc and 70 ± 49°, respectively. Perirectal distance, rV95 and rD_max 1 cc correlated with hydrogel angle θ (p < 0.01), and yet more strongly with the novel metric θ*hydrogel volume (p < 0.001). With a median follow up of 14 months, no rectal toxicity >grade 2 was observed. Low grade rectal toxicity was observed in a third of men and resolved within 1 month of SBRT. Men who had these symptoms had higher rD_max 1 cc and smaller θ*hydrogel volume measurements.

CONCLUSIONS

Optimal hydrogel placement occurs at prostate midgland, midline. The novel parameter θ*hydrogel volume describes a large proportion of rectum dosimetric benefit derived from hydrogel placement, and can be used to assess the learning curve phenomenon for hydrogel placement.

Predictive Factors of Late-onset Rectal Mucosal Changes After Radiotherapy of Prostate Cancer

BACKGROUND/AIM

The Vienna Rectoscopy Score (VRS; from 0, absence of rectal mucosal changes, to 5) assessed 1 year after radiotherapy is a surrogate end-point of late rectal toxicity. The aim of this study was to investigate the association between treatment-related factors and 1-year VRS.

PATIENTS AND METHODS

We performed a retrospective analysis of prospectively collected data. Patients with prostate adenocarcinoma treated with definitive or postoperative radiotherapy (RT) underwent endoscopy 1 year after RT. Relationships between VRS of 2 or more and treatment parameters were investigated by univariate and multivariate logistic analyses.

RESULTS

One hundred and ninety-five patients (mean age=69 years; range=43-81 years) were considered eligible for the study. At univariate analysis, patients treated with hypofractionation plus radiosurgery boost (p<0.001) and an equivalent dose in 2 Gy per fraction (EQD2) (α/β=3) ≥75 Gy (p<0.001) was associated with a significantly higher incidence of VRS ≥2 after 1 year of follow-up. At multivariate analysis, radiosurgery boost was an independent risk factor for developing rectal mucosal lesions (VRS ≥2), yielding an odds ratio (OR) of 4.14 (95% confidence interval (CI)=1.2-13.8), while pelvic surgery was inversely associated with VRS ≥2 (OR=0.39; 95% CI=0.17-0.94).

CONCLUSION

Hypofractionation followed by radiosurgery boost significantly increased the risk of developing late-onset rectal mucosal changes. Therefore, special care and preventative treatment strategies are needed when using radiosurgery boost after hypofractionated RT.

Radiotherapy dose-distribution to the perirectal fat space (PRS) is related to gastrointestinal control-related complications

Traditionally rectal symptoms following pelvic/prostate radiotherapy are correlated to the dosimetry of the anorectum or a substructure of this. It has been suggested that the perirectal fat space (PRS) surrounding the rectum may also be relevant. This study considers the delineation and dosimetry of the PRS related to both rectal bleeding and control-related toxicity. Initially, a case-control cohort of 100 patients from the RADAR study were chosen based on presence/absence of rectal control-related toxicity. Automated contouring was developed to delineate the PRS. 79 of the 100 auto-segmentations were considered successful. Balanced case-control cohorts were defined from these cases. Atlas of Complication Incidence (ACI) were generated to relate the DVH of the PRS with specific rectal symptoms; rectal bleeding and control-related symptoms (LENT/SOM). ACI demonstrated that control-related symptoms were related to the dose distribution to the PRS which was confirmed with Wilcoxon rank sum test (p < 0.05). To the authors knowledge this is the first study implicating the dose distribution to the PRS to the incidence of control-related symptoms of rectal toxicity.

Postoperative radiotherapy for prostate cancer: the sooner the better and potential to reduce toxicity even further

PURPOSE

To evaluate biochemical relapse-free survival (bRFS), overall survival (OS), late rectal and bladder toxicities in a retrospective single institution series, also applying an in-house software for biological dose calculation.

METHODS

258 patients submitted to radiotherapy after prostatectomy were considered. Differences between groups were calculated using the log-rank test and the relevant clinical and therapeutic variables were considered for multivariate analysis. PRODVH is an in-house system able to calculate mean dose-volume histograms (DVHs) of a series of patients, to convert them in biologically effective DVHs (BEDVHs) and allowing to compare them with ANOVA and t Student test.

RESULTS

Adjuvant radiotherapy (ART) and salvage radiotherapy (SRT) were performed in 131 (50.8%) and 127 patients (49.2%). At multivariate analysis advanced T stage, androgen deprivation total (ADT) and SRT resulted as independent variables related to a worst bRFS (p = 0.019, 0.001 and 0.02), while GS > 7 and SRT affected negatively OS (p 0.047 and 0.039). High grade toxicity events occurred mainly in patients treated with 3-dimensional conformal radiotherapy (3DCRT) (proctitis p = 0.006; cystitis: p = 0.041). A significantly more favorable mean rectum BEDVH for patients with G0 or G1 rectal toxicity was shown (p < 0.001). Mean BEDVH for both bladder (p < 0.01) and rectum (p < 0.05) were also significantly better for volumetric modulated arc therapy-image guided radiotherapy (VMAT-IGRT) plans than for 3DCRT plans.

CONCLUSION

ART is better than SRT in terms of bRFS and OS, particularly for more aggressive cases, advanced T stage and higher Gleason Score. Postoperative prostate cancer radiotherapy should be applied as soon as possible after surgery. The use of modern techniques such as VMAT-IGRT significantly reduces toxicity.

Dosimetric comparison of rectal-sparing capabilities of rectal balloon vs injectable spacer gel in stereotactic body radiation therapy for prostate cancer: lessons learned from prospective trials

This study aimed to compare the rectal-sparing capabilities of rectal balloons vs absorbable injectable spacer gel in stereotactic body radiation therapy (SBRT) for prostate cancer. Patient samples included in this analysis were obtained from 2 multi-institutional prospective trials of SBRT for prostate cancer using a rectal balloon (n = 36 patients) and injectable spacer gel (n = 36). Treatment prescription dose was 45 Gy in 5 fractions in 42 patients; for equal comparison, the remaining 30 patients were rescaled to 45 Gy from 47.5 Gy prescription (n = 6) and 50 Gy prescription (n = 24). The median prostate volumes and body mass index in the 2 patient samples were not statistically significantly different (p= 0.67 and 0.45, respectively), supporting anatomic similarity between cohorts. The injectable spacer gel achieved dosimetric superiority over the rectal balloon with respect to the maximum dose to the rectum (42.3 vs 46.2 Gy, p < 0.001), dose delivered to 33% of the rectal circumference (28 vs 35.1 Gy, p < 0.001), and absolute volume of rectum receiving 45 Gy (V45_Gy), V40_Gy, and V30_Gy (0.3 vs 1.7 cc, 1 vs 5.4 cc, and 4.1 vs 9.6 cc, respectively; p < 0.001 in all cases). There was no difference between the 2 groups with respect to the V50_Gy of the rectum or the dose to 50% of the rectal circumference (p= 0.29 and 0.06, respectively). The V18.3_Gy of the bladder was significantly larger with the rectal balloon (19.9 vs 14.5 cc, p= 0.003). In this analysis of patients enrolled on 2 consecutive multi-institutional prospective trials of SBRT for prostate cancer, the injectable spacer gel outperformed the rectal balloon in the majority of the examined and relevant dosimetric rectal-sparing parameters. The rectal balloon did not outperform the injectable spacer gel in any measured rectal dose parameter.

Decreased acute toxicities of intensity-modulated radiation therapy for localized prostate cancer with prostate-based versus bone-based image guidance

BACKGROUND

Intensity-modulated radiation therapy (IMRT) is a major therapeutic option for localized prostate cancer. Image-guided radiation therapy (IGRT) allows tumor visualization and corrects the errors caused by daily internal movement of the prostate. The current study retrospectively compared the acute toxicities and biochemical tumor control outcomes of prostate IMRT achieved using two IGRT techniques: bony structure-based IGRT (B-IGRT) and prostate-based IGRT (P-IGRT).

METHODS

Between February 2011 and July 2014, 96 patients with low- or intermediate-risk prostate cancer were treated using P-IGRT based on cone-beam computed tomography (CBCT; 76 Gy) without fiducial markers. This group of patients was compared with a similar cohort of 96 patients who were treated with B-IGRT (74 Gy) between July 2007 and September 2011. The planning target volume (PTV) margins were 1-3 mm smaller in the P-IGRT group than in the B-IGRT group.

RESULTS

The median follow-up periods for all patients, the P-IGRT group, and the B-IGRT group were 42, 32, and 64 months, respectively. A significantly lower incidence of acute grade 2 or higher gastrointestinal toxicities was observed in the P-IGRT group compared with the B-IGRT group (3 vs. 11%; p = 0.049). The prostate-specific antigen failure-free survival rates at 3 years were 95.5 and 92.7% for the P-IGRT and B-IGRT groups, respectively (p = 0.534).

CONCLUSIONS

IMRT with P-IGRT allows PTV margin reduction without sacrificing tumor control, which successfully reduces acute rectal toxicity compared with IMRT with B-IGRT.

Delivered dose can be a better predictor of rectal toxicity than planned dose in prostate radiotherapy

Background and purpose

For the first time, delivered dose to the rectum has been calculated and accumulated throughout the course of prostate radiotherapy using megavoltage computed tomography (MVCT) image guidance scans. Dosimetric parameters were linked with toxicity to test the hypothesis that delivered dose is a stronger predictor of toxicity than planned dose.

Material and methods

Dose–surface maps (DSMs) of the rectal wall were automatically generated from daily MVCT scans for 109 patients within the VoxTox research programme. Accumulated-DSMs, representing total delivered dose, and planned-DSMs, from planning CT data, were parametrised using Equivalent Uniform Dose (EUD) and ‘DSM dose-width’, the lateral dimension of an ellipse fitted to a discrete isodose cluster. Associations with 6 toxicity endpoints were assessed using receiver operator characteristic curve analysis.

Results

For rectal bleeding, the area under the curve (AUC) was greater for accumulated dose than planned dose for DSM dose-widths up to 70 Gy. Accumulated 65 Gy DSM dose-width produced the strongest spatial correlation (AUC 0.664), while accumulated EUD generated the largest AUC overall (0.682). For proctitis, accumulated EUD was the only reportable predictor (AUC 0.673). Accumulated EUD was systematically lower than planned EUD.

Conclusions

Dosimetric parameters extracted from accumulated DSMs have demonstrated stronger correlations with rectal bleeding and proctitis, than planned DSMs.

Rectal Toxicity After Extremely Hypofractionated Radiotherapy Using a Non-Isocentric Robotic Radiosurgery System for Early Stage Prostate Cancer

Background

The aim of the study was to evaluate toxicity after extremely hypofractionated radiotherapy (EHF-RT) using a non-isocentric robotic radiosurgery system for early stage prostate cancer.

Methods

Eligibility criteria of this feasibility study were 50 - 84 years old, and low-risk to intermediate-risk disease. The prescribed dose to the iso-dose line of 95% of planning target volume was 35 Gy in five fractions over 2 weeks. The primary endpoint was the incidence of ≥ grade 2 acute toxicity which indicated symptoms requiring medications.

Results

We enrolled 20 patients from December 2012 to August 2014, and the median follow-up time was 30 months (range: 18 - 36). Sixteen patients had a short overall treatment time (OTT) of EHF-RT (9 - 10 days), and four patients had a long OTT (11 - 12 days) because of national holidays and patient’s preference. The incidences of ≥ grade 2 acute toxicity in all sites, that in the rectum, and that in the genitourinary system, were 30%, 20%, and 10%, respectively. No patient developed severe acute toxicity (≥ grade 3). Among 16 patients with a short OTT of EHF-RT, four patients developed grade 2 acute rectal toxicity. Rectum-V_{28 Gy} (rectal volume receiving ≥ 28 Gy) of 3.8 mL or higher had a tendency to increase grade 2 acute rectal toxicity (P = 0.058). One patient developed grade 3 late rectal toxicity and no patient developed severe late genitourinary toxicity.

Conclusion

The incidences of ≥ grade 2 acute toxicity in all sites and that in the rectum after EHF-RT of 35 Gy in five fractions were 30% and 20%, respectively. High rectum-V_{28 Gy} was associated with grade 2 acute rectal toxicity after EHF-RT for early prostate cancer.

Predictive factors of rectal toxicity after permanent iodine-125 seed implantation: Prospective cohort study in 2339 patients

PURPOSE

To evaluate the incidence and the associated factors of rectal toxicity in patients with prostate cancer undergoing permanent seed implantation (PI) with or without external beam radiation therapy (EBRT) in a nationwide prospective cohort study in Japan (J-POPS) during the first 2 years.

METHODS AND MATERIALS

A total of 2,339 subjects were available for the analyses. Rectal toxicity was evaluated using the National Cancer Institute Common Terminology Criteria for Adverse Events version 3.0.

RESULTS

The 3-year cumulative incidence for grade ≥2 rectal toxicity was 2.88%, 1.76%, and 6.53% in all subjects, PI group and EBRT combination therapy group, respectively. On multivariate analysis, among all subjects, grade ≥2 rectal toxicity was associated with rectal volumes receiving 100% of the prescribed dose (R₁₀₀; p < 0.0001) and EBRT combination therapy (p = 0.0066). R₁₀₀ in the PI group (p = 0.0254), and R₁₀₀ (p = 0.0011) and interactive planning (p = 0.0267) in the EBRT combination therapy group were also associated with grade ≥2 toxicity. The 3-year cumulative incidence of grade ≥2 rectal toxicity was 3.80% and 1.37% for R₁₀₀ ≥ 1 mL and R₁₀₀ < 1 mL, respectively, in the PI group (p = 0.0068), and 14.09% and 5.52% for R₁₀₀ ≥ 1 mL and R₁₀₀ < 1 mL, respectively, in the EBRT combination therapy group (p = 0.0070).

CONCLUSIONS

Rectal toxicity was relatively rare in this study compared with previous reports. For Japanese prostate cancer patients, R₁₀₀ < 1 mL in both PI and EBRT combination therapy groups and interactive planning in EBRT combination therapy group may be effective in decreasing the incidence of rectal toxicity.

Comparative study of late rectal toxicity in prostate cancer patients treated with low-dose-rate brachytherapy: With or without supplemental external beam radiotherapy

PURPOSE

Supplemental external beam radiation therapy (sEBRT) is often prescribed in men undergoing low-dose-rate (LDR) brachytherapy. A population of patients was analyzed to assess the effect of sEBRT on late rectal toxicity. It was hypothesized that sEBRT + LDR would be associated with a higher risk of late rectal toxicity.

METHODS AND MATERIALS

This retrospective cohort study examined LDR brachytherapy patients, treated with or without sEBRT, with a minimum of 5-year followup. Longitudinal assessments were evaluated using the computerized patient record system. The Kaplan-Meier method was used for analysis.

RESULTS

Median followup was 7.5 years for 245 patients from 2004 to 2007. sEBRT was administered to 33.5%. Followup beyond 5 years was available for 89%. Overall rates of Grade ≥2 and ≥3 rectal toxicities were 6.9% and 2.9%, respectively. The risk of Grade ≥2 rectal toxicity was 2.8-fold higher for patients receiving sEBRT (95% confidence interval: 1.1-7.2; p = 0.02). The risk of Grade ≥3 rectal toxicity was 11.9-fold higher for patients who received sEBRT (1.5-97.4, 95% confidence interval; p = 0.003). Six of seven patients with a Grade ≥3 rectal toxicity received sEBRT, including one who required an abdominoperineal resection. Median post-LDR D90, V150, V200, and R100 values were 103.3%, 59.4%, 30.1%, and 0.5 cc.

CONCLUSIONS

In a cohort of LDR brachytherapy patients with high rates of followup, sEBRT + LDR was associated with significantly higher risk of Grade ≥2 and ≥3 late rectal toxicity. This analysis supports previous findings and maintains concern about the supplemental use of external beam radiation therapy with LDR brachytherapy while its benefit for tumor control has yet to be prospectively validated.

Late rectal toxicity after low-dose-rate brachytherapy: incidence, predictors, and management of side effects

As clinical outcomes for patients with clinically localized prostate cancer continue to improve, patients and physicians are increasing making treatment decisions based on concerns regarding long-term morbidity. A primary concern is late radiation proctitis, a clinical entity embodied by various signs and symptoms, ranging from diarrhea to rectal fistulas. Here, we present a comprehensive literature review examining the clinical manifestations and pathophysiology of late radiation proctitis after low-dose-rate brachytherapy (BT), as well as its incidence and predictors. The long-term risks of rectal bleeding after BT are on the order of 5-7%, whereas the risks of severe ulceration or fistula are on the order of 0.6%. The most robust predictor appears to be the volume of rectum receiving the prescription dose. In certain situations (e.g., salvage setting, for patients with increased radiosensitivity, and following aggressive biopsy after BT), the risk of these severe toxicities may be increased by up to 10-fold. A variety of excellent management options exist for rectal bleeding, with endoscopic methods being the most commonly used.

[Prostate-rectum spacers: optimization of prostate cancer irradiation]

In the curative radiotherapy of localized prostate cancer, improvements in biochemical control observed with dose escalation have been counterbalanced by an increase in radiation-induced toxicity. The injection of biodegradable spacers between prostate and rectum represents a new frontier in the optimization of radiotherapy treatments for patients with localized disease. Transperineal injection of different types of spacers under transrectal ultrasound guidance allows creating a 7-to-20 mm additional space between the prostate and the anterior rectal wall lasting 3 to 12 months. Dosimetrically, a relative reduction in the rectal volume receiving at least 70 Gy (V70) in the order of 43% to 84% is observed with all types of spacers, regardless of the radiotherapy technique used. Preliminary clinical results show for all spacers a good tolerance and a possible reduction in the acute side effects rate. The aim of the present systematic review of the literature is to report on indications as well as dosimetric and clinical advantages of the different types of prostate-rectum spacers commercially available (hydrogel, hyaluronic acid, collagen, biodegradable balloon).

Late rectal and bladder toxicity following radiation therapy for prostate cancer: Predictive factors and treatment results

AIM

This study aimed at investigating factors associated to late rectal and bladder toxicity following radiation therapy and the effectiveness of Hyperbaric Oxygen Therapy (HBOT) when toxicity is grade ≥2.

BACKGROUND

Radiation is frequently used for prostate cancer, but a 5-20% incidence of late radiation proctitis and cystitis exists. Some clinical and dosimetric factors have been defined without a full agreement. For patients diagnosed of late chronic proctitis and/or cystitis grade ≥2 treatment is not well defined. Hyperbaric Oxygen Therapy (HBOT) has been used, but its effectiveness is not well known.

MATERIALS AND METHODS

257 patients were treated with radiation therapy for prostate cancer. Clinical, pharmacological and dosimetric parameters were collected. Patients having a grade ≥2 toxicity were treated with HBOT. Results of the intervention were measured by monitoring toxicity by Common Toxicity Criteria v3 (CTCv3).

RESULTS

Late rectal toxicity was related to the volume irradiated, i.e. V50 > 53.64 (p = 0.013); V60 > 38.59% (p = 0.005); V65 > 31.09% (p = 0.002) and V70 > 22.81% (p = 0.012). We could not correlate the volume for bladder. A total of 24 (9.3%) patients experienced a grade ≥2. Only the use of dicumarinic treatment was significant for late rectal toxicity (p = 0.014). A total of 14 patients needed HBOT. Final percentage of patients with a persistent toxicity grade ≥2 was 4.5%.

CONCLUSION

Rectal volume irradiated and dicumarinic treatment were associated to late rectal/bladder toxicity. When toxicity grade ≥2 is diagnosed, HBOT significantly ameliorate symptoms.

Genome-wide association study identifies a region on chromosome 11q14.3 associated with late rectal bleeding following radiation therapy for prostate cancer

BACKGROUND AND PURPOSE

Rectal bleeding can occur following radiotherapy for prostate cancer and negatively impacts quality of life for cancer survivors. Treatment and clinical factors do not fully predict rectal bleeding, and genetic factors may be important.

MATERIALS AND METHODS

A genome-wide association study (GWAS) was performed to identify SNPs associated with the development of late rectal bleeding following radiotherapy for prostate cancer. Logistic regression was used to test the association between 614,453 SNPs and rectal bleeding in a discovery cohort (79 cases, 289 controls), and top-ranking SNPs were tested in a replication cohort (108 cases, 673 controls) from four independent sites.

RESULTS

rs7120482 and rs17630638, which tag a single locus on chromosome 11q14.3, reached genome-wide significance for association with rectal bleeding (combined p-values 5.4×10(-8) and 6.9×10(-7) respectively). Several other SNPs had p-values trending toward genome-wide significance, and a polygenic risk score including these SNPs shows a strong rank-correlation with rectal bleeding (Sommers' d=5.0×10(-12) in the replication cohort).

CONCLUSIONS

This GWAS identified novel genetic markers of rectal bleeding following prostate radiotherapy. These findings could lead to the development of a predictive assay to identify patients at risk for this adverse treatment outcome so that dose or treatment modality could be modified.