Interrater agreement of contouring of the neurovascular bundles and internal pudendal arteries in neurovascular-sparing magnetic resonance-guided radiotherapy for localized prostate cancer

Young oncologists benefit more than experts from deep learning-based organs-at-risk contouring modeling in nasopharyngeal carcinoma radiotherapy: A multi-institution clinical study exploring working experience and institute group style factor

Background

To comprehensively investigate the behaviors of oncologists with different working experiences and institute group styles in deep learning-based organs-at-risk (OAR) contouring.

Methods

A deep learning-based contouring system (DLCS) was modeled from 188 CT datasets of patients with nasopharyngeal carcinoma (NPC) in institute A. Three institute oncology groups, A, B, and C, were included; each contained a beginner and an expert. For each of the 28 OARs, two trials were performed with manual contouring first and post-DLCS edition later, for ten test cases. Contouring performance and group consistency were quantified by volumetric and surface Dice coefficients. A volume-based and a surface-based oncologist satisfaction rate (VOSR and SOSR) were defined to evaluate the oncologists' acceptance of DLCS.

Results

Based on DLCS, experience inconsistency was eliminated. Intra-institute consistency was eliminated for group C but still existed for group A and group B. Group C benefits most from DLCS with the highest number of improved OARs (8 for volumetric Dice and 10 for surface Dice), followed by group B. Beginners obtained more numbers of improved OARs than experts (7 v.s. 4 in volumetric Dice and 5 v.s. 4 in surface Dice). VOSR and SOSR varied for institute groups, but the rates of beginners were all significantly higher than those of experts for OARs with experience group significance. A remarkable positive linear relationship was found between VOSR and post-DLCS edition volumetric Dice with a coefficient of 0.78.

Conclusions

The DLCS was effective for various institutes and the beginners benefited more than the experts.

Deep learning for automated contouring of neurovascular structures on magnetic resonance imaging for prostate cancer patients

Background and purpose

Manual contouring of neurovascular structures on prostate magnetic resonance imaging (MRI) is labor-intensive and prone to considerable interrater disagreement. Our aim is to contour neurovascular structures automatically on prostate MRI by deep learning (DL) to improve workflow and interrater agreement.

Materials and methods

Segmentation of neurovascular structures was performed on pre-treatment 3.0 T MRI data of 131 prostate cancer patients (training [n = 105] and testing [n = 26]). The neurovascular structures include the penile bulb (PB), corpora cavernosa (CCs), internal pudendal arteries (IPAs), and neurovascular bundles (NVBs). Two DL networks, nnU-Net and DeepMedic, were trained for auto-contouring on prostate MRI and evaluated using volumetric Dice similarity coefficient (DSC), mean surface distances (MSD), Hausdorff distances, and surface DSC. Three radiation oncologists evaluated the DL-generated contours and performed corrections when necessary. Interrater agreement was assessed and the time required for manual correction was recorded.

Results

nnU-Net achieved a median DSC of 0.92 (IQR: 0.90-0.93) for the PB, 0.90 (IQR: 0.86-0.92) for the CCs, 0.79 (IQR: 0.77-0.83) for the IPAs, and 0.77 (IQR: 0.72-0.81) for the NVBs, which outperformed DeepMedic for each structure (p < 0.03). nnU-Net showed a median MSD of 0.24 mm for the IPAs and 0.71 mm for the NVBs. The median interrater DSC ranged from 0.93 to 1.00, with the majority of cases (68.9%) requiring manual correction times under two minutes.

Conclusions

DL enables reliable auto-contouring of neurovascular structures on pre-treatment MRI data, easing the clinical workflow in neurovascular-sparing MR-guided radiotherapy.

Current Knowledge on Radiation-Therapy-Induced Erectile Dysfunction in Prostate-Cancer Patients: A Narrative Review

Prostate cancer is the most frequently diagnosed cancer in men in the United States. Among the different available treatment options, radiation therapy is recommended for localized or even advanced disease. Erectile dysfunction (ED) often occurs after radiation therapy due to neurological, vascular, and endocrine mechanisms resulting in arterial tone alteration, pudendal-nerve neuropraxia, and lastly fibrosis. Considering the influence of quality of life on patients’ treatment choice, radiation-therapy-induced ED prevention and treatment are major issues. In this narrative review, we briefly summarize and discuss the current state of the art on radiation-therapy-induced ED in PCa patients in terms of pathophysiology and available treatment options.

Daily online contouring and re-planning versus translation-only correction in neurovascular-sparing magnetic resonance-guided radiotherapy for localized prostate cancer

Neurovascular bundle (NVB) and internal pudendal artery (IPA) sparing during magnetic resonance-guided radiotherapy (MRgRT) for prostate cancer aims for preservation of erectile function. Our present workflow involves daily online contouring and re-planning on a 1.5 T MR-linac, as alternative to conventional (rigid) translation-only corrections of the prostate. We compared planned dose for the NVB and IPA between strategies. Total planned dose was significantly lower with daily online contouring and re-planning for the NVB, but not for the IPA. For the NVB and IPA, the intrapatient difference between highest and lowest fraction dose was significantly smaller for the contouring and re-planning plans.

Neurovascular-Sparing MR-Guided Adaptive Radiotherapy in Prostate Cancer; Defining the Potential Population for Erectile Function-Sparing Treatment

BACKGROUND

Magnetic resonance-guided adaptive radiotherapy (MRgRT) enables neurovascular-sparing treatment for localized prostate cancer (PCa). The aim of this treatment is preservation of erectile function by sparing the neurovascular bundles, the internal pudendal arteries, the corpora cavernosa, and the penile bulb. Internal pudendal arteries, corpora cavernosa, and penile bulb sparing can generally be achieved in all patients, but NVB sparing can be challenging due to its proximity to the prostate and is therefore dependent on tumor location. PCa patients that have sufficient erectile function at baseline and favorable tumor characteristics might benefit from this treatment. Currently, it is unclear what proportion of patients are eligible for neurovascular-sparing treatment and to what extent this is technically feasible.

AIM

To define the eligibility and technical feasibility for neurovascular-sparing MRgRT in intermediate-risk localized PCa patients.

METHODS

A consecutive series of men that received 5 × 7.25 gray (Gy) MRgRT for localized PCa were included. Baseline erectile function was assessed using the International Index of Erectile Function (IIEF)-5 questionnaire. Additionally, the ability of sparing the neurovascular bundles was assessed in all patients. Per neurovascular-sparing protocol, the dominant intraprostatic lesion with a 4 mm isotropic margin should receive 34.44 Gy in ≥ 99% of the volume (i.e., high-dose area). When the high-dose area directly borders or overlaps the NVB because of a dorsolateral position of the dominant intraprostatic lesion, sparing of the NVB was considered not feasible on that side.

OUTCOMES

Patient-reported IIEF-5 baseline questionnaires and the technical feasibility of NVB sparing were assessed.

RESULTS

Of the 102 men that completed the IIEF-5 questionnaire at baseline, 49.0% of patients reported to have an IIEF-5 score of ≥ 17. In those patients, the NVB could technically have been spared bilaterally in 20.0% and unilaterally in 68.0%.

CLINICAL IMPLICATIONS

Our findings define the potential population for neurovascular-sparing MRgRT for localized PCa and indicate the proportion in which the NVB can technically be spared.

STRENGTH & LIMITATIONS

The major strength of this study is the prospective collection of data. The limitations include that the neurovascular-sparing feasibility definition is based on pre-clinical planning data.

CONCLUSION

A substantial group of 49.0% of patients in our study had mild or no erectile dysfunction at baseline. Of these patients, the NVB could technically have been spared bilaterally in 20.0% and unilaterally in 68.0% during MRgRT. Trials need to assess the effect of neurovascular-sparing MRgRT on erectile function. Teunissen FR, van der Voort van Zyp JRN, Verkooijen HM, et al., Neurovascular-Sparing MR-Guided Adaptive Radiotherapy in Prostate Cancer; Defining the Potential Population for Erectile Function-Sparing Treatment. J Sex Med 2022;19:1196-1200.

Erectile dysfunction following hydrogel injection and hypofractionated radiotherapy for prostate cancer: Our experience in 56 cases

INTRODUCTION

The incidence of erectile dysfunction (ED) in men with organ-confined prostate cancer (PCa) submitted to hypofractionated radiotherapy (HRT) has been prospectively evaluated.

MATERIALS AND METHODS

From April 2018 to September 2020, 56 patients (median age 70 years) with cT1c PCa were treated by HRT directed to the prostate and seminal vesicle. Median PSA was 8.3 ng/ml; 20 patients (35.7%) vs. 28 (50%) vs. 8 (22.3%) had a PCa Grade Group 1 vs. 2 vs. 3, respectively. All patients underwent hydrogel injection of Space OAR and intraprostatic fiducials before HRT. The prescription dose was 60 Gy in 20 fractions 5 days/week over 4 weeks. During the follow up, PSA, genitourinary (GU) and gastrointestinal (GI) toxicities were evaluated. The sexual function was evaluated by International Index of Erectile Function - 5 (IIEF-5) before, 6 and 18 months from HRT; 32/56 (57.1%) men referred a normal sexual activity before HRT (median IIEF-5 score: 22).

RESULTS

Median PSA level at median follow up of 18 months was 0.92 ng/ml and none used adjuvant therapy. One man (1.8%) referred a tardive grade 1 GU complication. At a median follow up of 6 and 18 months, 20/32 (62.5%) kept pretreatment sexual potency (median IIEF-5 score: 21). The 12/32 men who worsened the sexual function following HRT had a median age higher than patients without ED (78 vs. 67 years).

CONCLUSIONS

The use of hydrogel injection and intraprostatic fiducials followed by HRT allowed to kept pretreatment sexual potency in 62.5% of the cases.