Dosimetric predictors for genitourinary toxicity in MR-guided stereotactic body radiation therapy (SBRT): Substructure with fraction-wise analysis

BACKGROUND

MR-guided radiation therapy (MRgRT) systems provide superior soft tissue contrast than x-ray based systems and can acquire real-time cine for treatment gating. These features allow treatment planning margins to be reduced, allowing for improved critical structure sparing and reduced treatment toxicity. Despite this improvement, genitourinary (GU) toxicity continues to affect many patients.

PURPOSE

(1) To identify dosimetric predictors, potentially in combination with clinical parameters, of GU toxicity following SBRT by leveraging MRgRT to accurately monitor daily dose, beyond predicted dose calculated during planning. (2) Improve awareness of toxicity-sensitive bladder substructures, specifically the trigone and urethra.

METHODS

Sixty-nine prostate cancer patients (NCT04384770 clinical trial) were treated on a ViewRay MRIdian MRgRT system, with 40 Gy prescribed to 95% of the PTV in over five fractions. Overall, 17 (24.6%) prostate patients reported acute grade 2 GU toxicity. The CTV, PTV, bladder, bladder wall, trigone, urethra, rectum, and rectal wall were contoured on the planning and daily treatment MRIs. Planning and daily treatment DVHs (0.1 Gy increments), organ doses (min, max, mean), and organ volumes were recorded. Daily dose was estimated by transferring the planning dose distributions to the daily MRI based on the daily setup alignment. Patients were partitioned into a training (55) and testing set (14). Dose features were pre-filtered using a t-test followed by maximum relevance minimum redundancy (MRMR) algorithm. Logistic regression was investigated with regularization to select dosimetric predictors. Specifically, two approaches: time-group least absolute shrinkage and selection (LASSO), and interactive grouped greedy algorithm (IGA) were investigated. Shared features across the planning and five treatment fractions were grouped to encourage consistency and stability. The conventional flat non-temporally grouped LASSO was also evaluated to provide a solid benchmark. After feature selection, a final logistic regression model was trained. Dosimetric regression models were compared to a clinical regression model with only clinical parameters (age, baseline IPSS, prostate gland size, ADT usage, etc.) and a hybrid model, combining the best performing dosimetric features with the clinical parameters, was evaluated. Final model performance was evaluated on the testing set using accuracy, sensitivity, and specificity determined by the optimal threshold of the training set.

RESULTS

IGA had the best testing performance with an accuracy/sensitivity/specificity of 0.79/0.67/0.82, selecting 12 groups covering the bladder (V19.8 Gy, V20.5 Gy), bladder wall (19.7 Gy), trigone (15.9, 18.2, 43.3 Gy), urethra (V41.4 Gy, V41.7 Gy), CTV (V41.9 Gy), rectum (V8.5 Gy), and rectal wall (1.2, 44.1 Gy) dose features. Absolute bladder V19.8 Gy and V20.5 Gy were the most important features, followed by relative trigone 15.9  and 18.2 Gy. Inclusion of clinical parameters in the hybrid model with IGA did not significantly change regression performance.

CONCLUSION

Overall, IGA feature selection resulted in the best GU toxicity prediction performance. This exploratory study demonstrated the feasibility of identification and analysis of dosimetric toxicity predictors with awareness to sensitive substructures and daily dose to potentially provide consistent and stable dosimetric metrics to guide treatment planning. Further patient accruement is warranted to further assess dosimetric predictor and perform validation.

Prophylactic intraventricular piping method prevents entrapped temporal horn after removal of ventricle trigone meningioma: technical note

BACKGROUND

Entrapped temporal horn (ETH) is one of the critical complications after tumor removal in the lateral ventricle trigone that sometimes becomes life-threatening.

OBJECTIVE

To develop a novel intraoperative method of prophylactic intraventricular piping (PIP) just after tumor removal to prevent ETH.

METHODS

Three patients with meningiomas in the lateral ventricle trigone were treated by a novel intraoperative method of PIP just after tumor removal to prevent ETH. Silicone catheters normally used as ventricular drainage catheters were cut to 5-6 cm length and inserted into the tumor cavity to ensure communication between the temporal horn and the atrium or the body of the lateral ventricle through the piping straddling the trigone.

RESULTS

None of our patients developed ETH during the follow-up period without complications caused by the tube placement.

CONCLUSIONS

PIP might be beneficial to prevent ETH because constant osmotic pressure and constant cerebrospinal fluid pulse wave transmission are maintained between each compartment of the lateral ventricle.

Does urinary urgency drive urinary frequency in overactive bladder?

OBJECTIVES

To determine if reduction in urgency in patients with refractory overactive bladder syndrome (rOAB) is correlated with a reduction in voiding frequency and symptom bother.

METHODS

Data from a prospective series of women with rOAB undergoing radiofrequency ablation of the subtrigonal tissue, termed selective bladder denervation (SBD), was analyzed. Main outcome measures included urgency voids, nonurgency voids, and urgency urinary incontinence (UUI) epidsodes from a 3-day voiding diary and quality of life (QoL) measures (Overactive Bladder Questionnaire Short Form [OAB-q SF]).

RESULTS

The dataset comprised 62 completer subjects at 6 months. Compared to baseline, UUI and urgency voids were lower (P < .001), but nonurgency voids were increased (P < .001) and QoL measures were improved (P < .001), but functional bladder capacity did not increase. At baseline and 6 months post treatment, symptom bother was correlated with urgency voids (P < .05) but inversely correlated with nonurgency voids (P < .001). Urgency and nonurgency voids were inversely related at baseline and at 6 months (P < .0001). Following treatment, urgency voids decreased by 41% and nonurgency voids increased by 33%.

CONCLUSIONS

As with other interventions for OAB, SBD resulted in a reduction in OAB symptoms and an improvement in QoL measures. However, the decrease in urgency voids was offset by an increase in nonurgency voids, suggesting that habit or defensive voiding is a significant driver of urinary frequency. It is not certain if this is a unique finding of the SBD effect, but these data do suggest that analyses of outcomes of other OAB interventions are warranted to gain a better understanding of the genesis of OAB symptoms.

Induction of bacterial cystitis in female rabbits by uropathogenic Escherichia coli and the differences between the bladder dome and trigone

This study is designed to evaluate the histological effects of uropathogenic Escherichia coli (UPEC) infection in the urinary bladder of female rabbits and compare the differences between the dome and trigone. Bacterial cystitis was induced in 13 female rabbits by transurethral inoculation of UPEC into the urinary bladder. Eight animals served as controls. Urine samples were collected by catheterization and cultured for bacterial growth after 12 and 24 hours then every 48 hours. Infection was defined as ≥(1X10⁵) colony-forming unit/ml of UPEC in the first two urine samples. Bladder dome and trigonal specimens were examined by light and scanning electron microscopy eight days after infection. There was a sustained increase in bacterial count, with urethral bleeding and rabbit weakness suggesting bladder colonization in the 10/13 study group (77%). Infection was not demonstrated in two animals and was spontaneously cleared in the third after 48 hours. No control animals developed an infection. In infected rabbits (n = 10), the dome showed inflammatory changes including the epithelial loss or thinning, inflammatory cell infiltration, and congested blood vessels compared to controls. The trigone showed a more pronounced inflammatory response than the dome. The presence of urinary bacterial growth, infection manifestations, and inflammatory changes that were more severe in the trigone than in the dome indicate successful bacterial inoculation and induction of cystitis. This animal model can be used for clinical trials on female cystitis. Our histological findings support a possible role of trigone in the pathogenesis of urinary tract infection.

Hyperuricosuria, hematuria, and novel bladder images with IgA nephropathy

Episodic (recurrent) macroscopic hematuria in patients with IgA nephropathy is usually associated with a benign prognosis, although some patients experience a transient fall in glomerular filtration rate during the episodes. We present a 15-year-old girl with mild IgA nephropathy who had multiple episodes of macroscopic hematuria associated with severe but transient decreases in estimated glomerular filtration rate, low levels of serum uric acid, and marked increases in fractional excretion of uric acid. Ultrasound studies showed marked inflammatory changes in the bladder, especially involving the trigone. Cystoscopic findings were consistent with these changes. We hypothesize that the macroscopic hematuria may have resulted, at least in part, from hyperuricosuria causing acute irritation of the bladder mucosa in the trigone area.

One-year results with selective bladder denervation in women with refractory overactive bladder

AIMS

To report 1-year results with selective bladder denervation (SBD) of the trigone in women with refractory overactive bladder (OAB).

METHODS

In this prospective, international, multicenter case series, women with refractory OAB underwent a single SBD treatment of the bladder subtrigone region using temperature-controlled radiofrequency. Patients were followed for 1 year and evaluated for changes in OAB symptoms and adverse events.

RESULTS

Among 35 women, 29 (83%) returned for 1-year follow up. Median symptom reductions based on 3-day bladder diaries were 68% for urgency urinary incontinence ( P < .001), 67% for urinary incontinence ( P < .001), 43% for urgency episodes ( P < .001), 5% for urinary frequency ( P = .19), and 33% for the total urgency and frequency score ( P < .001), with the majority of treatment benefit realized in the first month. Treatment benefit was reported in 72% of patients, the clinical success rate (≥50% reduction in urgency urinary incontinence) was 69%, and the dry rate was 10%. Statistically significant improvements occurred on Symptom Bother and Health-related Quality of Life scales on the Overactive Bladder questionnaire, and on 6 of 9 King's Health Questionnaire domains. Patients with less severe baseline symptoms had similar quality of life improvements as those with more severe baseline symptoms. Device- or procedure-related adverse events were reported in 6 (17%) patients.

CONCLUSIONS

A single treatment with selective bladder denervation is durable for 1-year in a significant proportion of women with refractory overactive bladder.

Initial clinical experience with selective bladder denervation for refractory overactive bladder

Aims

To report the initial clinical experience with selective bladder denervation (SBD) of the trigone in women with refractory overactive bladder (OAB).

Methods

Females with refractory OAB underwent SBD of the bladder sub‐trigone region. Patients were treated using a 10‐s voltage‐controlled radiofrequency (RF) algorithm (RF10) at study onset. The protocol was modified during the study after which point remaining patients received 60‐s temperature‐controlled RF (RF60). Patients were followed for 12 weeks and evaluated for adverse events and changes in OAB symptoms. Exploratory analyses on the influence of RF duration were performed.

Results

Among 63 patients, SBD resulted in statistically significant and clinically important improvements for most outcomes. Comparing RF10 (n = 34) to RF60 (n = 29), treatment benefit was greater with RF60 including mean reduction in urgency urinary incontinence (−2.5 vs −0.9; P < 0.01), urinary incontinence (−2.6 vs −0.8; P < 0.001), and total urgency and frequency score (−13 vs −7; P = 0.02); and improvements in symptom bother (−33 vs −18; P < 0.01) and quality of life (28 vs 16; P = 0.02) on the OAB questionnaire. The proportion of urgency urinary incontinence treatment responders (≥50% reduction in episodes) was 79% with RF60 and 31% with RF10. The frequency of device‐ or procedure‐related adverse events was comparable in RF10 versus RF60 groups (14.7% vs 17.2%).

Conclusions

This study demonstrated the feasibility of SBD in alleviating symptoms of refractory OAB. A 60‐s RF algorithm using deeper ablations of the sub‐trigonal tissues was more effective and comparably safe to a 10‐s RF algorithm using more superficial ablations.

An Investigation of Dosimetric Correlates of Acute Toxicity in Prostate Stereotactic Body Radiotherapy: Dose to Urinary Trigone is Associated with Acute Urinary Toxicity

AIMS

There are limited data on dosimetric correlates of toxicity in stereotactic body radiotherapy (SBRT) for prostate cancer. We aimed to identify potential relationships between dose and toxicity using conventional dose-volume histograms (DVHs) and dose-surface maps (DSMs).

MATERIALS AND METHODS

Urinary bladder trigone and rectum DSMs were produced for a single-institution service evaluation cohort of 50 patients receiving SBRT for localised prostate cancer, together with conventional DVHs for bladder and rectum. Patients had been prospectively recruited to this cohort and treated according to a pre-defined protocol to a dose of 36.25 Gy in five fractions. Radiation Therapy Oncology Group (RTOG) and International Prostate Symptom Score (IPSS) toxicity data were recorded prospectively. Logistic regression was used to identify dosimetric predictors of acute IPSS+10 (rise of 10 points or more above baseline) and grade 2+ RTOG toxicity.

RESULTS

On univariate analysis, trigone area receiving 40 Gy and trigone Dmax were associated with IPSS+10 (odds ratio 1.06 [1.02-1.11], P = 0.007 and odds ratio 1.54 [1.06-2.25], P = 0.024, respectively). These two variables were highly correlated. In a multivariate model, including all baseline variables, trigone Dmax remained associated with IPSS+10 (odds ratio 1.91 [1.13-3.22], P = 0.016). These findings were not significant with Holm-Bonferroni correction for multiple testing (corrected P value threshold 0.006). No associations were seen between rectal toxicity and DVH or DSM parameters.

CONCLUSIONS

Our study suggests a potential relationship between high doses to the urinary bladder trigone and patient-reported urinary toxicity in prostate SBRT, and is consistent with previous studies in conventionally fractionated radiotherapy, justifying further evaluation in larger cohorts.

Adreno-muscarinic synergy in the male human urinary outflow tract

AIM

To examine putative interaction between adrenergic and muscarinic contractile activation in the human urinary outflow tract.

METHODS

Tissue from the trigone and prostatic urethra was obtained from 12 cystectomy and 16 prostatectomy specimen. Contractions were elicited by exposure to exogenous agonists before and after inhibition of Rho kinase and protein kinase c (PKC). Immunofluorescence and Western-blot studies were performed using antibodies to muscarinic M3-receptors (M3-R) and alpha1A-adrenoreceptors (alpha1A-AR). The study is registered with ClinicalTrials.gov, number NCT01227447.

RESULTS

There was strong co-localization of M3-R and alpha1A-AR on trigonal and urethral myocytes. Western blot analysis revealed a significantly higher expression of alpha1A-AR in the superficial than in the deep trigone. Phenylephrine (PE, 1 μm) augmented contractions induced by carbachol (CA, 3 μm) to more than threefold control in the male superficial trigone, and to about sevenfold control in the proximal urethra. No such potentiation could be detected in female bladder outlet. Both PKC inhibitor GF 109203X and Rho kinase inhibitor Y-27632 reduced responses to 1 μM PE as well as to 3 μM CA significantly. However, the synergistic effect of the combined intervention remained proportionally unaffected.

CONCLUSIONS

Muscarinic and adrenergic receptor activation exerts a strong synergistic effect in the male human bladder trigone and proximal urethra.

Ethnic variation in deep lateral orbital anatomy and its implications on decompression surgery

AIM

To describe differences in the deep lateral orbital wall (specifically, trigone) between Chinese, Malay, Indian and Caucasian subjects Methods: Single-centre retrospective Computed Tomogram (CT)-based study; 20 subjects of each ethnicity were used from existing databases, matched for gender, average age and laterality. Subjects below 16 years of age were excluded. DICOM image viewing software CARESTREAM Vue PACS (Carestream Health Inc., USA) and OsiriX version 7.5 (Pixmeo., Switzerland) were used to measure deep lateral wall length, thickness and volume, as well as orbital depth and statistical analyses performed using Statistical Package for Social Sciences version 21 (IBM, USA).

RESULTS

In each group, there were 12 males (60%) and average age was not significantly different (p = 0.682-0.987). Using Chinese subjects as a reference, in Chinese, Malay, Indian and Caucasian subjects, mean trigone thickness was 13.68, 14.02, 11.60 (p < 0.001) and 13.80 mm, curved total wall length 45.23, 42.29 (p = 0.048), 41.91 (p = 0.020) and 45.00 mm, curved trigone length 23.03, 22.61, 17.19 (p = 0.011) and 18.76 mm (p = 0.030) and trigone volume 3120.97, 3221.01, 1613.66 (p < 0.001), 2498.46 mm³ (p = 0.059) respectively. Similarly, perpendicular orbital depth was 27.54, 24.97, 22.12 (p = 0.001) and 25.93 mm and diagonal orbital depth was 34.19, 33.27, 29.48 (p = 0.01) and 34.63 mm respectively.

CONCLUSIONS

Indian and, to a lesser extent, Caucasian subjects have smaller trigones compared to their Chinese and Malay counterparts. Indian subjects also have shallower orbits and due care should be taken during decompression surgery.

Prostaglandin D2 effects and DP1 /DP2 receptor distribution in guinea pig urinary bladder out-flow region

The proximal urethra and urinary bladder trigone play important roles in continence. We have previously shown that PGD₂ is released from guinea pig bladder urothelium/suburothelium and can inhibit detrusor contractile responses. We presently wished to investigate PGD₂ actions in guinea pig out‐flow region and the distribution of DP₁/DP₂ receptors. The effects of PGD₂ on urothelium‐intact trigone and proximal urethra contractility were studied in organ bath experiments. Expression of DP₁/DP₂ receptor proteins was analysed by western blot. Immunohistochemistry was used to identify distribution of DP₁/DP₂ receptors. PGD₂ in a dose‐dependent manner inhibited trigone contractions induced by electrical field stimulation (EFS) and inhibited spontaneous contractions of the proximal urethra. PGD₂ was equally (trigone) or slightly less potent (urethra) compared with PGE₂. Expression of DP₁ and DP₂ receptors was found in male guinea pig bladder trigone, neck and proximal urethra. In the trigone and proximal urethra, DP₁ receptors were found on the membrane of smooth muscle cells and weak immunoreactivty was observed in the urothelium. DP₂ receptors were distributed more widespread, weakly and evenly in the urothelium and smooth muscles. Inhibitory effects by PGD₂ on motor activity of guinea pig trigone and proximal urethra are consistent with finding DP₁ and DP₂ receptors located in the urothelium and smooth muscle cells of the trigone and proximal urethra, and PGD₂ may therefore be a modulator of the bladder out‐flow region, possibly having a function in regulation of micturition and a role in overactive bladder syndrome.

Trigone ventricular meningiomas: Is it possible to achieve good results even in the absence of high tech tools?

BACKGROUND

Intraventricular meningiomas constitute 2% of intracranial meningiomas, representing a challenging disease for neurosurgeons; we report our experience through a case series, emphasizing surgical approaches and results.

METHODS

Between 2009 and 2012, four patients underwent microsurgical resection in our department. Clinical and imaging findings, surgical approaches, outcomes, and follow-up were analyzed.

RESULTS

Four patients (three females and one male) were included and the signs of intracranial hypertension were the main clinical presentation in all cases. The parietal approach through intraparietal sulcus was performed in 3 cases and parieto-occipital interhemispheric surgical route in 1 case. Gross total resection was achieved in all the patients without additional deficits and without the aid of neuronavigation, intraoperative monitoring, and intraoperative magnetic resonance imaging.

CONCLUSION

Gross total resection is the gold standard treatment for such tumors and the intraparietal sulcus approach is an excellent choice for most of the cases. Careful anatomical knowledge contributes to a safer procedure even in the absence of high tech equipment assistance.

Posterior interhemispheric transfalcine transprecuneus approach for microsurgical resection of periatrial lesions: indications, technique, and outcomes

OBJECT

Surgical exposure of the peritrigonal or periatrial region has been challenging due to the depth of the region and overlying important functional cortices and white matter tracts. The authors demonstrate the operative feasibility of a contralateral posterior interhemispheric transfalcine transprecuneus approach (PITTA) to this region and present a series of patients treated via this operative route.

METHODS

Fourteen consecutive patients underwent the PITTA and were included in this study. Pre- and postoperative clinical and radiological data points were retrospectively collected. Complications and extent of resection were reviewed.

RESULTS

The mean age of patients at the time of surgery was 39 years (range 11-64 years). Six of the 14 patients were female. The mean duration of follow-up was 4.6 months (range 0.5-19.6 months). Pathology included 6 arteriovenous malformations, 4 gliomas, 2 meningiomas, 1 metastatic lesion, and 1 gray matter heterotopia. Based on the results shown on postoperative MRI, 1 lesion (7%) was intentionally subtotally resected, but ≥ 95% resection was achieved in all others (93%) and gross-total resection was accomplished in 7 (54%) of 13. One patient (7%) experienced a temporary approach-related complication. At last follow-up, 1 patient (7%) had died due to complications of his underlying malignancy unrelated to his cranial surgery, 2 (14%) demonstrated a Glasgow Outcome Scale (GOS) score of 4, and 11 (79%) manifested a GOS score of 5.

CONCLUSIONS

Based on this patient series, the contralateral PITTA potentially offers numerous advantages, including a wider, safer operative corridor, minimal need for ipsilateral brain manipulation, and better intraoperative navigation and working angles.

Posterior interhemispheric transfalcine transprecuneus approach for microsurgical resection of periatrial lesions: indications, technique, and outcomes

OBJECT

Surgical exposure of the peritrigonal or periatrial region has been challenging due to the depth of the region and overlying important functional cortices and white matter tracts. The authors demonstrate the operative feasibility of a contralateral posterior interhemispheric transfalcine transprecuneus approach (PITTA) to this region and present a series of patients treated via this operative route.

METHODS

Fourteen consecutive patients underwent the PITTA and were included in this study. Pre- and postoperative clinical and radiological data points were retrospectively collected. Complications and extent of resection were reviewed.

RESULTS

The mean age of patients at the time of surgery was 39 years (range 11-64 years). Six of the 14 patients were female. The mean duration of follow-up was 4.6 months (range 0.5-19.6 months). Pathology included 6 arteriovenous malformations, 4 gliomas, 2 meningiomas, 1 metastatic lesion, and 1 gray matter heterotopia. Based on the results shown on postoperative MRI, 1 lesion (7%) was intentionally subtotally resected, but ≥ 95% resection was achieved in all others (93%) and gross-total resection was accomplished in 7 (54%) of 13. One patient (7%) experienced a temporary approach-related complication. At last follow-up, 1 patient (7%) had died due to complications of his underlying malignancy unrelated to his cranial surgery, 2 (14%) demonstrated a Glasgow Outcome Scale (GOS) score of 4, and 11 (79%) manifested a GOS score of 5.

CONCLUSIONS

Based on this patient series, the contralateral PITTA potentially offers numerous advantages, including a wider, safer operative corridor, minimal need for ipsilateral brain manipulation, and better intraoperative navigation and working angles.