Validation of T2- and diffusion-weighted magnetic resonance imaging for mapping intra-prostatic tumour prior to focal boost dose-escalation using intensity-modulated radiotherapy (IMRT)

Efficiency and Accuracy Evaluation of Multiple Diffusion-Weighted MRI Techniques Across Different Scanners

BACKGROUND

The choice between different diffusion-weighted imaging (DWI) techniques is difficult as each comes with tradeoffs for efficient clinical routine imaging and apparent diffusion coefficient (ADC) accuracy.

PURPOSE

To quantify signal-to-noise-ratio (SNR) efficiency, ADC accuracy, artifacts, and distortions for different DWI acquisition techniques, coils, and scanners.

STUDY TYPE

Phantom, in vivo intraindividual biomarker accuracy between DWI techniques and independent ratings.

POPULATION/PHANTOMS

NIST diffusion phantom. 51 Patients: 40 with prostate cancer and 11 with head-and-neck cancer at 1.5 T FIELD STRENGTH/SEQUENCE: Echo planar imaging (EPI): 1.5 T and 3 T Siemens; 3 T Philips. Distortion-reducing: RESOLVE (1.5 and 3 T Siemens); Turbo Spin Echo (TSE)-SPLICE (3 T Philips). Small field-of-view (FOV): ZoomitPro (1.5 T Siemens); IRIS (3 T Philips). Head-and-neck and flexible coils.

ASSESSMENT

SNR Efficiency, geometrical distortions, and susceptibility artifacts were quantified for different b-values in a phantom. ADC accuracy/agreement was quantified in phantom and for 51 patients. In vivo image quality was independently rated by four experts.

STATISTICAL TESTS

QIBA methodology for accuracy: trueness, repeatability, reproducibility, Bland-Altman 95% Limits-of-Agreement (LOA) for ADC. Wilcoxon Signed-Rank and student tests on P < 0.05 level.

RESULTS

The ZoomitPro small FOV sequence improved b-image efficiency by 8%-14%, reduced artifacts and observer scoring for most raters at the cost of smaller FOV compared to EPI. The TSE-SPLICE technique reduced artifacts almost completely at a 24% efficiency cost compared to EPI for b-values ≤500 sec/mm2 . Phantom ADC 95% LOA trueness were within ±0.03 × 10-3  mm2 /sec except for small FOV IRIS. The in vivo ADC agreement between techniques, however, resulted in 95% LOAs in the order of ±0.3 × 10-3  mm2 /sec with up to 0.2 × 10-3  mm2 /sec of bias.

DATA CONCLUSION

ZoomitPro for Siemens and TSE SPLICE for Philips resulted in a trade-off between efficiency and artifacts. Phantom ADC quality control largely underestimated in vivo accuracy: significant ADC bias and variability was found between techniques in vivo.

LEVEL OF EVIDENCE

3 TECHNICAL EFFICACY STAGE: 2.

Standard and Hypofractionated Dose Escalation to Intraprostatic Tumor Nodules in Localized Prostate Cancer: 5-Year Efficacy and Toxicity in the DELINEATE Trial

PURPOSE

Our purpose was to report 5-year efficacy and toxicity of intraprostatic lesion boosting using standard and hypofractionated radiation therapy.

METHODS AND MATERIALS

DELINEATE (ISRCTN 04483921) is a single center phase 2 multicohort study including standardly fractionated (cohort A: 74 Gy/37F to prostate and seminal vesicles [PSV]; cohort C 74 Gy/37F to PSV plus 60 Gy/37F to pelvic lymph nodes) and moderately hypofractionated (cohort B: 60 Gy/20F to PSV) prostate intensity-modulated radiation therapy patients with National Comprehensive Cancer Network intermediate/high-risk disease. Patients received an integrated boost of 82 Gy (cohorts A and C) or 67 Gy (cohort B) to multiparametric magnetic resonance imaging identified lesion(s). Primary endpoint was late Radiation Therapy Oncology Group (RTOG) gastrointestinal (GI) toxicity at 1 year. Secondary endpoints were acute and late toxicity (clinician and patient reported) and freedom from biochemical/clinical failure at 5 years.

RESULTS

Two hundred and sixty-five men were recruited and 256 were treated (55 cohort A, 153 cohort B, and 48 cohort C). Median follow-up for each cohort was >5 years. Cumulative late RTOG grade 2+ GI toxicity at 1 year was 3.6% (95% confidence interval [CI], 0.9%-13.8%) (cohort A), 7.2% (95% CI, 4%-12.6%) (cohort B), and 8.4% (95% CI, 3.2%-20.8%) (cohort C). Cumulative late RTOG grade 2+ GI toxicity to 5 years was 12.8% (95% CI, 6.3%-25.1%) (cohort A), 14.6% (95% CI, 9.9%-21.4%) (cohort B), and 20.7% (95% CI, 11.2%-36.2%) (cohort C). Cumulative RTOG grade 2+ genitourinary toxicity to 5 years was 12.9% (95% CI, 6.4%-25.2%) (cohort A), 18.2% (95% CI, 12.8%-25.4%) (cohort B), and 18.2% (95% CI, 9.5%-33.2%) (cohort C). Five-year freedom from biochemical/clinical failure was 98.2% (95% CI, 87.8%-99.7%) (cohort A), 96.7% (95% CI, 91.3%- 98.8%) (cohort B), and 95.1% (95% CI, 81.6-98.7%) (cohort C).

CONCLUSIONS

The DELINEATE trial has shown safety, tolerability, and feasibility of focal boosting in 20 or 37 fractions. Efficacy results indicate a low chance of prostate cancer recurrence 5 years after radiation therapy. Evidence from ongoing phase 3 randomized trials is awaited.

Dosimetric Uncertainties in Dominant Intraprostatic Lesion Simultaneous Boost Using Intensity Modulated Proton Therapy

Purpose

While intensity modulated proton therapy can deliver simultaneous integrated boost (SIB) to the dominant intraprostatic lesion (DIL) with high precision, it is sensitive to anatomic changes. We investigated the dosimetric effects from these changes based on pretreatment cone-beam computed tomographic (CBCT) images and identified the most important factors using a multilayer perceptron neural network (MLPNN).

Methods and Materials

DILs were contoured based on coregistered multiparametric magnetic resonance images for 25 previously treated prostate cancer patients. SIB plans were created with (1) prostate clinical target volume − V70 Gy = 98%; (2) DIL − V98 Gy > 95%; and (3) all organs at risk (OARs)"?> within clinical constraints. SIB plans were applied to daily CBCT-based deformed planning computed tomography (CT)"?>. DIL − V98 Gy, bladder/rectum maximum dose (Dmax) and volume changes, femur shifts, and the distance from DIL to organs at riskOARs"?> in both planning computed tomogramsCT"?> and CBCT were calculated. Wilcoxon signed-ranks tests were used to compare the changes. MLPNNs were used to model the change in ΔDIL − V98 Gy > 10% and bladder/rectum Dmax > 80 Gy, and the relative importance factors for the model were provided. The performances of the models were evaluated with receiver operating characteristic curves.

Results

Comparing initial plan to the average from evaluation plans, respectively, DIL − V98 Gy was 89.3% ± 19.9% versus 86.2% ± 21.3% (P = .151); bladder Dmax 71.9 ± 0.6 Gy versus 74.5 ± 2.9 Gy (P < .001); and rectum Dmax 70.1 ± 2.4 Gy versus 74.9 ± 9.1Gy (P = .007). Bladder and rectal volumes were 99.6% ± 39.5% and 112.8% ± 27.2%, respectively, of their initial volume. The femur shift was 3.16 ± 2.52 mm. In the modeling of ΔDIL V98 Gy > 10%, DIL to rectum distance changes, DIL to bladder distance changes, and rectum volume changes ratio are the 3 most important factors. The areas under the receiver operating characteristic curves were 0.89, 1.00, and 0.99 for the modeling of ΔDIL − V98 Gy > 10%, and bladder and rectum Dmax > 80 Gy, respectively.

Conclusions

Dosimetric changes in DIL SIB with intensity modulated proton therapy can be modeled and classified based on anatomic changes on pretreatment images by an MLPNN.

Proton vs. photon radiotherapy for MR-guided dose escalation of intraprostatic lesions

BACKGROUND

Dose escalation has been associated with improved biochemical control for prostate cancer. Focusing the high dose on the MRI-defined intraprostatic lesions (IL) could spare the surrounding organs at risk and hence allow further escalation. We compare treatment efficacy between state-of-the-art focally-boosted proton and photon-based radiotherapy, and investigate possible predictive guidelines regarding individualized treatment prescriptions.

MATERIAL AND METHODS

Ten prostate cancer patients with well-defined ILs were selected. Multiparametric MRI was used to delineate ILs, which were transferred to the planning CT via image registration. Pencil beam scanning proton therapy and volumetric modulated arc therapy treatment plans, were created for each patient. Each modality featured 6 plans: (1) moderately hypofractionated dose: 70 Gy to the prostate in 28 fractions, (2)-(6) plan 1 plus additional simultaneous-integrated-boost to ILs to 75.6, 81.2, 86.6, 98 and 112 Gy in 28 fractions. Equivalent dose to 2 Gy-per-fraction (EqD2) was used to calculate tumor control (TCP) and normal tissue complication probabilities (NTCP) for ILs and organs-at-risk.

RESULTS

For both modalities, the maximum necessary dose to achieve TCP > 99% was 98 Gy for very high-risk ILs. For lower risk ILs lower doses were sufficient. NTCP was <25% and 35% for protons and photons at the maximum dose escalation, respectively. For the cases and beam characteristics considered, proton therapy was dosimetrically superior when IL was >4 cc or located <2.5 mm from the rectum.

CONCLUSION

This work demonstrated the potential role for proton therapy in the setting of prostate focal dose escalation. We propose that anatomical characteristic could be used as criteria to identify patients who would benefit from proton treatment.

A prospective comparative dosimetric study between diffusion weighted MRI (DWI) & T2-weighted MRI (T2W) for target delineation and planning in cervical cancer brachytherapy

Aim

To evaluate the difference between GTVBT (Gross Tumor Volume at Brachytherapy) and HR CTV (High Risk Clinical Tumor Volume) delineated with DWI and T2W MRI. To evaluate doses to organs at risk and targets from plans generated using T2W and DWI.

Background

Functional imaging with DWI can improve cervical tumor distinction as it is more sensitive than T2W MRI even in detecting parametrial invasion. This study does a dosimetric comparison between a T2W and DWI based plan.

Methods

Fifty carcinoma cervix patients were subjected to MRI based brachytherapy. T2W and a diffusion weighted sequence were acquired. Target delineation and brachytherapy planning was done on both T2W and DWI. Standard DVH parameters were recorded and the treatment was given using the plan generated from T2W images.

Results

GTVBT and HRCTV contours on DWI were different when compared with T2W. Mean GTVBT volume on T2W and DWI was 5.25 and 5.23, respectively (p value 0.8). Mean HRCTV on T2W and DWI was 28.3 and 27 cc, respectively (p value 0.003). Planning on the above volumes resulted in a superior coverage in terms of HRCTV D90 and D100 for DWI based plan, HRCTV D90 - 735.1 and 741 cGy for T2W and DWI, respectively (p value 0.006), HRCTV D100 - 441.05 and 444.5 for T2W and DWI plans, respectively (p value = 0.006). Doses to the OAR were not significantly increased.

Conclusion

GEC ESTRO based contouring guidelines cover all the functionally abnormal areas on DWI. DWI should only be used as a supplement to T2W for contouring target volumes.

Automatic intraprostatic lesion segmentation in multiparametric magnetic resonance images with proposed multiple branch UNet

PURPOSE

Contouring intraprostatic lesions is a prerequisite for dose-escalating these lesions in radiotherapy to improve the local cancer control. In this study, a deep learning-based approach was developed for automatic intraprostatic lesion segmentation in multiparametric magnetic resonance imaging (mpMRI) images contributing to clinical practice.

METHODS

Multiparametric magnetic resonance imaging images from 136 patient cases were collected from our institution, and all these cases contained suspicious lesions with Prostate Imaging Reporting and Data System (PI-RADS) score ≥ 4. The contours of the lesion and prostate were manually created on axial T2-weighted (T2W), apparent diffusion coefficient (ADC) and high b-value diffusion-weighted imaging (DWI) images to provide the ground truth data. Then a multiple branch UNet (MB-UNet) was proposed for the segmentation of an indistinct target in multi-modality MRI images. An encoder module was designed with three branches for the three MRI modalities separately, to fully extract the high-level features provided by different MRI modalities; an input module was added by using three sub-branches for three consecutive image slices, to consider the contour consistency among different image slices; deep supervision strategy was also integrated into the network to speed up the convergency of the network and improve the performance. The probability maps of the background, normal prostate and lesion were output by the network to generate the segmentation of the lesion, and the performance was evaluated using the dice similarity coefficient (DSC) as the main metric.

RESULTS

A total of 162 lesions were contoured on 652 image slices, with 119 lesions in the peripheral zone, 38 in the transition zone, four in the central zone and one in the anterior fibromuscular stroma. All prostates were also contoured on 1,264 image slices. As for the segmentation of lesions in the testing set, MB-UNet achieved a per case DSC of 0.6333, specificity of 0.9993, sensitivity of 0.7056; and global DSC of 0.7205, specificity of 0.9993, sensitivity of 0.7409. All the three deep learning strategies adopted in this study contributed to the performance promotion of the MB-UNet. Missing the DWI modality would degrade the segmentation performance more markedly compared with the other two modalities.

CONCLUSIONS

A deep learning-based approach with proposed MB-UNet was developed to automatically segment suspicious lesions in mpMRI images. This study makes it feasible to adopt boosting intraprostatic lesions in clinical practice to achieve better outcomes.

Moderately hypofractionated radiotherapy for localized prostate cancer: updated long-term outcome and toxicity analysis

PURPOSE

Evaluation of long-term outcome and toxicity of moderately hypofractionated radiotherapy using intensity-modulated radiotherapy (IMRT) with simultaneous integrated boost treatment planning and cone beam CT-based image guidance for localized prostate cancer.

METHODS

Between 2005 and 2015, 346 consecutive patients with localized prostate cancer received primary radiotherapy using cone beam CT-based image-guided intensity-modulated radiotherapy (IG-IMRT) and volumetric modulated arc therapy (IG-VMAT) with a simultaneous integrated boost (SIB). Total doses of 73.9 Gy (n = 44) and 76.2 Gy (n = 302) to the high-dose PTV were delivered in 32 and 33 fractions, respectively. The low-dose PTV received a dose (D95) of 60.06 Gy in single doses of 1.82 Gy. The pelvic lymph nodes were treated in 91 high-risk patients to 45.5 Gy (D95).

RESULTS

Median follow-up was 61.8 months. The 5‑year biochemical relapse-free survival (bRFS) was 85.4% for all patients and 93.3, 87.4, and 79.4% for low-, intermediate-, and high-risk disease, respectively. The 5‑year prostate cancer-specific survival (PSS) was 94.8% for all patients and 98.7, 98.9, 89.3% for low-, intermediate-, and high-risk disease, respectively. The 5‑year and 10-year overall survival rates were 83.8 and 66.3% and the 5‑year and 10-year freedom from distant metastasis rates were 92.2 and 88.0%, respectively. Cumulative 5‑year late GU toxicity and late GI toxicity grade ≥2 was observed in 26.3 and 12.1% of the patients, respectively. Cumulative 5‑year late grade 3 GU/GI toxicity occurred in 4.0/1.2%.

CONCLUSION

Moderately hypofractionated radiotherapy using SIB treatment planning and cone beam CT image guidance resulted in high biochemical control and survival with low rates of late toxicity.

Standard and Hypofractionated Dose Escalation to Intraprostatic Tumor Nodules in Localized Prostate Cancer: Efficacy and Toxicity in the DELINEATE Trial

PURPOSE

To report a planned analysis of the efficacy and toxicity of dose escalation to the intraprostatic dominant nodule identified on multiparametric magnetic resonance imaging using standard and hypofractionated external beam radiation therapy.

METHODS AND MATERIALS

DELINEATE is a single centre prospective phase 2 multicohort study including standard (cohort A: 74 Gy in 37 fractions) and moderately hypofractionated (cohort B: 60 Gy in 20 fractions) prostate image guided intensity modulated radiation therapy in patients with National Comprehensive Cancer Network intermediate- and high-risk disease. Patients received an integrated boost of 82 Gy (cohort A) and 67 Gy (cohort B) to lesions visible on multiparametric magnetic resonance imaging. Fifty-five patients were treated in cohort A, and 158 patients were treated in cohort B; the first 50 sequentially treated patients in cohort B were included in this planned analysis. The primary endpoint was late Radiation Therapy Oncology Group rectal toxicity at 1 year. Secondary endpoints included acute and late toxicity measured with clinician- and patient-reported outcomes at other time points and biochemical relapse-free survival for cohort A. Median follow-up was 74.5 months for cohort A and 52.0 months for cohort B.

RESULTS

In cohorts A and B, 27% and 40% of patients, respectively, were classified as having National Comprehensive Cancer Network high-risk disease. The cumulative 1-year incidence of Radiation Therapy Oncology Group grade 2 or worse rectal and urinary toxicity was 3.6% and 0% in cohort A and 8% and 10% in cohort B, respectively. There was no reported late grade 3 rectal toxicity in either cohort. Within cohort A, 4 of 55 (7%) patients had biochemical relapse.

CONCLUSIONS

Delivery of a simultaneous integrated boost to intraprostatic dominant nodules is feasible in prostate radiation therapy using standard and moderately hypofractionated regimens, with rectal and genitourinary toxicity comparable to contemporary series without an intraprostatic boost.

Seven or less Fractions is Not the Standard of Care for Intermediate-Risk Prostate Cancer

Evidence is accumulating for seven and less fractions in localised prostate cancer, including one large randomised trial. However, there is much more evidence yet to come and changing practice in advance of this may be premature. We review the reasons to persist with moderate hypofractionation for prostate cancer radiotherapy, until the results of further phase III studies are known.