F18-DCFPyL PSMA-PET/CT vs. mpMRI for Localizing the Gross Target Volume for Radiotherapy in Prostate Cancer

PURPOSE/OBJECTIVE(S)

Local recurrences in prostate cancer (Pca) after radiotherapy generally occur in the site of dominant tumor burden, and recent evidence based on multi parametric (mpMRI) supports tumor-targeted escalation of dose to improve biochemical disease-free survival outcomes. With the recent emergence of prostate cancer targeted radiotracers, we hypothesize that PSMA-PET and mpMRI may not equally depict the pathological gross target volume (pGTV) at risk of recurrence after radiotherapy.

MATERIALS/METHODS

Subjects who underwent both mpMRI and 18F DCFPyl PSMA-PET/CT prior to radiotherapy were identified from a prospective REB-approved registry. Patients who were naive to radiotherapy and patients with local recurrences were evaluated. Each patient underwent standard of care systematic biopsies prior to imaging and treatment. Sextants from prostate biopsy were analyzed on an independent basis. Per previous published work, pGTV at risk of recurrence was defined as the pathological dominant lesions with peak PCL (percentage core length) involvement and any sextants with ≽ 40% PCL involvement. Each imaging method was analyzed independently to determine spatial correspondence of the visible tumor to pGTV at risk of recurrence. Lesions scored 4-5 (PIRADSv2.1) were identified on mpMRI. For PSMA-PET, regions with uptake higher than the adjacent background with scaling SUVmin-max 0-10 were identified.

RESULTS

Forty-seven patients with histopathological proven intermediate to high-risk Pca represented the study cohort. Of the 320 sextants, 135 were involved with PCa. Thirty-six percent (17∕47) of patients had a history of prior radiotherapy. PSMA-PET identified the pGTV in 89% (42∕47) of patients, while mpMRI yielded a higher detection rate at 98% (46∕47) (89% vs 98% p = 0.038). The only pGTV not detected on mpMRI was also missed by PSMA-PET, and had received EBRT in 2011. Of the four other pGTVs at risk of recurrence missed by PSMA-PET, three had no history of prior radiotherapy and one was treated with brachytherapy in 2005. Overall, we found no differences in imaging detection rates between previously treated and untreated patients. More detailed volumetric analyses are ongoing and will be presented.

CONCLUSION

mpMRI may provide superior detection of the pGTV at risk of recurrence in comparison to PSMA-PET. Until further research is completed, clinicians should exercise caution in omitting mpMRI and utilizing PSMA-PET as the sole imaging method for GTV targeting.

MR-Guided HDR Brachytherapy Boost in Localized Prostate Cancer - Results of a Phase II Trial

PURPOSE/OBJECTIVE(S)

Dose escalation in localized prostate cancer using brachytherapy combined with external beam radiation (EBRT) has demonstrated improved biochemical control compared to EBRT alone. However, ultrasound guided LDR brachytherapy might be associated with increased GU toxicity. We report the results of a prospective study of MR-guided HDR brachytherapy (MRgHDR) in combination with EBRT for localized prostate cancer.

MATERIALS/METHODS

Intermediate- (IR) and high-risk (HR) prostate cancer patients were eligible. Patients received either 15Gy single fraction or 10Gy x 2 fractions using MRgHDR technique, followed by EBRT (37.5 Gy, [prostate only] -IR or 45-46 Gy - [prostate + pelvic nodes] -HR). Toxicity (CTCAE v4) and HRQoL (EPIC) were recorded at 1, 3 and 6 months, then at 1, 2, 3, and 5 years. Androgen deprivation therapy (ADT) was used according to the appropriate disease risk category. Biochemical failure was defined according to Phoenix definition (nadir+2).

RESULTS

From 2010-2018, 120 patients were enrolled, 53 (44%) had IR and 67 (56%) had HR disease. Median age was 69 years (range, 46-78), median PSA was 12.1 ng/ml (3.2-148). ADT was used in 84 (70%) of patients, of whom 51 (60%) patients received <1 year and 33 (40%) received >1 year of ADT. A single fraction of 15Gy was given to 94 patients (78%) and the remaining 26 patients (22%) received 10Gy x 2 fractions. EBRT dose was 37.5Gy in 52 (43%) patients while 67 (56%) received 45-46Gy. One patient received only the first fraction of 10Gy, declined the second fraction and subsequently received 60Gy EBRT to the prostate. The median follow up was 58 months (11-134). Overall, 5-year biochemical control was 90% while it was 95% and 86% for IR and HR, respectively. At 5 years 7% patient had nodal or distant relapse or both. While the 5-yr distant control rates were 95% and 91% in the IR, HR, respectively. Acute grade ≥2 GU and GI toxicity was 6.7% and 5% respectively. Acute toxicity trended back to baseline by 6 months in all patients except one. Late grade ≥ 2 GU and GI worst toxicity was seen in 10% and 4.2%, respectively. As with acute toxicity, late toxicity tended to improve over time. Only one patient experienced severe toxicity (Grade 3 GU - frequency) at 6 months but subsequently this resolved. HRQol will be reported separately.

CONCLUSION

MRgHDR brachytherapy boost in conjunction with EBRT provides comparable biochemical outcomes compared to the literature. Severe toxicity rates were minimal. Further follow-up will determine if these outcomes are sustained.

Symptomatic Posttreatment Edema after Stereotactic Radiotherapy for Intracranial Meningiomas: Patterns and Predictive Factors

PURPOSE/OBJECTIVE(S)

Symptomatic posttreatment edema (SPTE) is a complication that may develop after radiotherapy for intracranial meningiomas. Our study aims at reviewing rates of SPTE in a large cohort of a single institution and identifying possible predictive factors.

MATERIALS/METHODS

We retrospectively analyzed data of 293 patients with 304 intracranial meningiomas irradiated at our institution between 2005 and 2018. We evaluated rates of SPTE and investigated numerous factors by univariate and multivariate analysis. Kaplan Meier analysis was used for estimation of actuarial local control and overall survival.

RESULTS

Median age was 60 years. Meningiomas were treated with fractionated stereotactic radiation therapy (70%), single fraction stereotactic radiosurgery (24%) or fractionated stereotactic radiosurgery (6%). Median imaging follow-up was 60 months, actuarial 10-year local control rate for patients with grade 1 meningiomas who received radiotherapy as definitive treatment was 99%. Local control at 5 years was 94% for grade 1 meningioma, 57% and 53% for grade 2 and 3 respectively. Sixteen patients (5.5%) developed SPTE, median time to onset was 3 months (range, 1-26 months). On univariate analysis, age > 60 years (p > 0.03), pre-treatment peritumoral edema (p = 0.014), medline location (p = 0.018), tumor size > 30 mm (p = 0.015) and grade 2 histology (p = 0.03) were predictive of SPTE. On multivariate analysis, only tumor location and size remained statistically significant.

CONCLUSION

Based on our results, patients at high risk of SPTE can be identified based on patient and tumor characteristics. The best treatment technique in high-risk patients is yet to be defined.

Estimation of blood lead levels in the French population using two complementary approaches: Esteban (2014-2016) as part of the human biomonitoring program and the national surveillance system for childhood lead poisoning (2015-2018)

BACKGROUND

Used widely for centuries, lead is a common environmental pollutant. As a cumulative toxic, its presence in the body is always evidence of exposure, and health effects occur without threshold. Though regulated by European directives, lead requires close monitoring due to its environmental persistence and toxicity.

METHODS

The first data source was the French surveillance system for monitoring childhood lead poisoning, which records the screening results of children (-18 years), providing data on their temporal and geographical distribution, characteristics, and risk factors. The second data source was Esteban, a cross-sectional study conducted in 2014-2016 on a random sample of the French population as part of the human biomonitoring program. The Esteban lead study concerns 904 children (6-17 years) and 999 adults (18-74 years), providing data on biological samples, sociodemographic characteristics, occupational exposure, environmental and dietary factors.

RESULTS

The surveillance system highlighted that lead poisoning affected 10% of children screened between 2015 and 2018. The main risk factor remains housing. Esteban confirmed this observation, finding a general mean of blood lead level (BLL) at 9.9 and 18.5 μg/L for children and adults, respectively. In children, parents' occupation increased BLLs. In adults, the greatest exposure factors were smoking, age, place of residence, alcohol, bread-based products, and homegrown livestock products. In both, drinking tap water and year of housing construction increased BLLs.

CONCLUSIONS

The surveillance system showed a high number of children with lead poisoning despite the implementation of prevention measures, which mainly concern lead paints in old and degraded homes. To help identify children at risk, healthcare providers need to know about exposure from housing and the emerging sources identified in the Esteban survey. Despite lower BLLs, the well-known risk factors of lead exposure persist, meaning prevention efforts must continue in order to limit their impact on the population.

Allergens labeling on French processed foods - an Oqali study

The French Observatory of Food Quality (Oqali) aims at collecting all nutritional data provided on labels of processed foods (nutritional information and composition), at branded products level, in order to follow nutritional labeling changes over time. This study carries out an overview of allergens labeling frequencies by distinguishing allergens used in recipes from those listed on precautionary statements, for the fourteen allergen categories for which labeling is mandatory according to European legislation. 17,309 products were collected, between 2008 and 2012, from 26 food categories. Products were classified per family and type of brand (national brands, retailer brands, entry‐level retailer brands, hard discount, and specialized retailer brands). Allergenic ingredients were identified from ingredients lists and precautionary statements. 73% of the 17,309 products studied contained at least one allergen in their ingredients list and 39% had a precautionary statement for one or more allergens. Milk (53%), gluten (41%), and egg (22%) were the most commonly used allergens in ingredients lists. For precautionary statement, nuts (20%), egg (14%), peanut (13%), soybean (12%), and milk (11%) were the most common allergens listed. Precautionary statement was most frequently found among first‐price products (hard discount and entry‐level retailer brands). National brands seemed to use it less frequently. For all these results, differences depended both on food categories and allergen categories. This study will enable to follow allergens labeling and their use as ingredients over time, particularly by assessing an hypothetical increase in allergens presence in processed food.

Plasma osteopontin as a biomarker of prostate cancer aggression: relationship to risk category and treatment response

BACKGROUND

High plasma osteopontin (OPN) has been linked to tumour hypoxia, metastasis, and poor prognosis. This study aims to assess whether plasma osteopontin was a biomarker of increasing progression within prostate cancer (PCa) prognostic groups and whether it reflected treatment response to local and systemic therapies.

METHODS

Baseline OPN was determined in men with localised (n=199), locally recurrent (n=9) and castrate-resistant, metastatic PCa (CRPC-MET; n=37). Receiver-operating curves (ROC) were generated to describe the accuracy of OPN for distinguishing between localised risk groups or localised vs metastatic disease. We also measured OPN pre- and posttreatment, following radical prostatectomy, external beam radiotherapy (EBRT), androgen deprivation (AD) or taxane-based chemotherapy.

RESULTS

The CRPC-MET patients had increased baseline values (mean 219; 56-513 ng ml(-1); P<0.0001) compared with the localised, non-metastatic group (mean 72; 12-438 ng ml(-1)). The area under the ROC to differentiate localised vs metastatic disease was improved when OPN was added to prostate-specific antigen (PSA) (0.943-0.969). Osteopontin neither distinguished high-risk PCa from other localised PCa nor correlated with serum PSA at baseline. Osteopontin levels reduced in low-risk patients after radical prostatectomy (P=0.005) and in CRPC-MET patients after chemotherapy (P=0.027), but not after EBRT or AD.

CONCLUSION

Plasma OPN is as good as PSA at predicting treatment response in CRPC-MET patients after chemotherapy. Our data do not support the use of plasma OPN as a biomarker of increasing tumour burden within localised PCa.

Prostate cancer hypoxia as a predictor of early biochemical and local failure after radiotherapy

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Background: Tumor hypoxia is an important determinant of patient outcome in many human malignancies, and has been associated with radioresistance and the development of metastases. The aim of this study was to determine the predictive effect of hypoxia in prostate cancer patients treated with RT.

Methods: A total of 256 patients with clinically localized prostate cancer underwent pre-treatment, transrectal, ultrasound-guided measurement of tumor oxygen using a needle electrode. The median pO2 (mpO2) was 6.7 mm Hg and the median hypoxic proportion <10 mm Hg (HP10) was 0.63. Most patients were treated with IMRT to the prostate alone using doses in the range of 75.6-79.8 Gy. Sixty-one received neoadjuvant and concurrent hormonal therapy. The Phoenix definition of biochemical relapse was used, and the median follow-up was 5.4 years.

Results: The 5-year bRFR was 78%. High PSA and Gleason score were independently associated with biochemical relapse, and formed the baseline clinical multivariate model. The effect of hypoxia was found to vary with the duration of patient follow- up. HP10, when added to the clinical multivariate model as a time-dependent variable, was a significant, independent predictor of early bRFR (p=0.015). The predictive effect of hypoxia diminished with increasing follow-up and was lost by 36 to 48 months. The relationship between hypoxia and early biochemical recurrence was more pronounced when the analysis was restricted to 144 patients with bulk tumor at the site of the oxygen measurements (p=0.008). Prostate biopsy was performed in 73 patients a median of 36 months after completing RT. Hypoxia was the only factor predictive of local recurrence in this sub-group, with the effect being greatest early in follow-up (p=0.038).

Conclusions: This is the largest clinical study of prostate cancer hypoxia with direct measurement of tumor oxygen levels. It suggests that hypoxia in the index tumor increases the risk of recurrence early after completing RT but not at longer times. The results imply a complex interaction between hypoxia and local vs. distant failure, which may be better elucidated with longer follow-up.

No significant financial relationships to disclose.

Can MRI accurately define tumor boundaries to guide focal salvage after radiotherapy?

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Background: We evaluated the role of MRI (plus/minus biopsy) in delineating tumour boundaries for focal salvage therapy of prostate cancer recurrence after external beam radiotherapy.

Methods: Patients with biochemical failure after radiotherapy were enrolled in a prospective clinical trial mapping sites of local recurrence. An integrated diagnostic MRI and interventional mapping biopsy procedure was performed under sedation in a 1.5T scanner. Patients were imaged with a pelvic coil and an endorectal coil attached to a stereotactic transperineal template assembly. Multiparametric MRI images were acquired, followed by targeted radial biopsy of suspicious regions and random sextant sampling of the normal-appearing peripheral zone. Histology maps were generated by delineation and registration of biopsy cores onto diagnostic images using point-based rigid image registration. Two independent blinded observers reviewed images offline and delineated tumours boundaries which were compared against overlaid histology maps. Coverage was considered accurate if all pathologically proven tumour sites were encompassed within delineated boundaries.

Results: Of the 18 patients analysed to date, the majority (83%) were found to have local recurrence. Patients with <6 informative cores were excluded, leaving 15 patients for analysis. Observers performed comparably, whereby mean MRI sensitivity, specificity, PPV and NPV for detecting tumor was 0.76, 0.7, 0.7, and 0.75. The MRI tumour boundary was accurate in 5/15 patients, and improved to 8/15 patients with addition of a 5-mm expansion margin. Targeted radial biopsies improved accuracy to 14/15 patients, by excluding false positive regions (n=2), increasing tumor volumes (n=2) or both (n=2). Random sampling biopsy was only relevant in 1 patient by detecting tumor not identified by MRI and targeted biopsy.

Conclusions: MRI alone is not sufficiently accurate to define boundaries for tumor-targeted salvage even with addition of an uncertainty margin. Targeted biopsy improved both detection and delineation accuracy for recurrent tumor regions, and changed salvage therapy planning in 40% of patients.

No significant financial relationships to disclose.