Detection Rate of 18F-rhPSMA-7.3 PET in Patients with Suspected Prostate Cancer Recurrence at PSA Levels <1 ng/mL: Data from the Phase 3 SPOTLIGHT Study

PURPOSE/OBJECTIVE(S)

Novel molecular imaging agents yield potential for localization of disease in patients with biochemical recurrence of prostate cancer when PSA levels are still low, and may facilitate early intervention with selective therapy to optimize outcomes. Radiohybrid (rh) positron emission tomography (PET) radiopharmaceutical, 18F-rhPSMA-7.3, is a novel high affinity prostate-specific membrane antigen (PSMA)-targeting ligand with potential for low bladder activity. The SPOTLIGHT study (NCT04186845) evaluated the diagnostic performance of 18F-rhPSMA-7.3 in men with suspected prostate cancer recurrence. Here, we report findings from a post-hoc analysis of SPOTLIGHT data, which determined the 18F-rhPSMA-7.3 detection rates (DR) at low-very low PSA levels.

MATERIALS/METHODS

Patients enrolled in SPOTLIGHT underwent PET 50-70 min after IV administration of 296 MBq 18F-rhPSMA-7.3. Scans were evaluated by 3 blinded central readers, with the majority read representing agreement between ≥2 independent readers. For the present analysis, all patients with an evaluable 18F-rhPSMA-7.3 PET and who had a baseline PSA <1 ng/mL were selected. Overall (patient-level) and regional DR by majority read were determined, stratifying DR according to the patients' baseline PSA level (<0.2, ≥0.2 - <0.3, ≥0.3 - <0.5, and ≥0.5 - <1 ng/mL).

RESULTS

In total, 389 patients (median [range] PSA, 1.10 [0.03-135] ng/mL, 84 with intact prostate) had an evaluable 18F-rhPSMA-7.3 scan. The overall DR was 83% (322/389) by majority read. Of the 389 patients with an evaluable 18F-rhPSMA-7.3 scan, 188 had a baseline PSA <1 ng/mL and were eligible for the present analysis. Despite low patient numbers in some PSA categories, moderate to high DR were observed, with the patient-level DR shown to increase with increasing baseline PSA (see table). Overall, 68% (128/188) of patients with a PSA <1 ng/mL and 64% (77/121) of patients with a PSA <0.5 ng/mL had a positive 18F-rhPSMA-7.3 scan by majority read. Regional DR were broadly consistent across all PSA categories. Of note, extrapelvic lesions were observed in 21% (25/121) of patients with a PSA <0.5 ng/mL and 27% (51/188) of all patients with a PSA <1 ng/mL.

CONCLUSION

Among this cohort of patients with low-very low PSA levels, more than two-thirds were found to have positive 18F-rhPSMA-7.3 scans. Of clinical significance, over a quarter of patients had extrapelvic findings. 18F-rhPSMA-7.3 PET may be a useful tool for treatment planning in patients with early biochemical recurrence of prostate cancer where curative salvage therapy is of prime consideration.

Biochemical Relapse-Free Survival in Post-Prostatectomy Patients Receiving 18F-Fluciclovine-Guided Prostate Bed Only Radiation: Post-Hoc Analysis of a Prospective Randomized Trial

PURPOSE/OBJECTIVE(S)

Whole pelvis (WP) radiation therapy (XRT) significantly improved biochemical relapse free survival (bRFS) compared to prostate-bed (PB)-only XRT in RTOG 0534, yet increased toxicity and was performed in an era prior to PET staging (Pollack et al, Lancet, 2022). Separately, 18F-fluciclovine PET/CT (PET)-guided post-prostatectomy XRT demonstrated improved bRFS compared to XRT guided by conventional imaging alone. We hypothesized that patients whose decisions were changed from whole pelvic XRT to PB-only XRT after PET imaging would have bRFS that was (a) not significantly different than patients initially planned for PB-only XRT, and (b) significantly improved over patients planned for WP XRT without PET guidance.

MATERIALS/METHODS

We conducted a post-hoc analysis of a prospective, randomized, single-institution trial comparing conventional (Arm A) v. PET-guided (Arm B) post-prostatectomy XRT. For patients randomized to Arm B, pre-PET treatment field decisions were recorded, and post-fluciclovine fields were rigidly defined per protocol: pN0 patients with no pelvic or extrapelvic PET uptake received PB-only XRT. Three- and four-year bRFS were compared in patients initially planned for WP with change to PB-only XRT [Arm B (WP→PB)] v Arm B patients initially planned for PB-only with final XRT to PB-only [Arm B(PB→PB)] & Arm A patients treated with whole pelvic XRT [Arm A(WP)] using Z test and log-rank test. Demographics were compared using Chi-square test, Fisher's exact test, or ANOVA as appropriate.

RESULTS

We identified 10 Arm B (WP→PB), 31 Arm B (PB→PB), and 25 Arm A (WP) patients. Androgen deprivation was used in 50.0% of Arm B (WP→PB) and 3.2% of Arm B (PB→PB) patients, p<0.01. Mean pre-XRT PSA was significantly higher (1.56 v 0.32 ng/mL, respectively, p<0.01) in Arm B (WP→PB) v Arm B (PB→PB) patients, however, there was no significant difference in extracapsular extension (p = 1.00), seminal vesical invasion (p = 1.00), Gleason score ≥8 (p = 0.58) or margin positivity (p = 0.73) between cohorts. Three- and four-year bRFS was 80% in Arm B (WP→PB) & 87.4% in Arm B (PB→PB), p = 0.47, respectively. Arm A (WP) patients had significantly worse three- (35.2%) and four-year (13.2%) bRFS compared to Arm B (WP→PB), p<0.01.

CONCLUSION

Patients initially planned for WP XRT whose treatment field decisions were changed to PB-only XRT after PET guidance had, in this post-hoc analysis, (a) relapse rates not significantly different than patients initially planned for PB-only XRT and (b) improved relapse rates over patients treated with WP XRT without PET guidance. PET-guided volume de-escalation in selected patients may be one approach to mitigating excess toxicity seen with WP XRT without compromising outcomes and warrants further exploration.

Rapid Unpaired CBCT-Based Synthetic CT for CBCT-Guided Adaptive Radiotherapy

PURPOSE/OBJECTIVE(S)

Quantitative cone beam CT (CBCT) is the foundation for image-guided radiation therapy, improving treatment setup, tumor delineation and dose calculation. However, CBCT images suffer from severe artifacts, limiting clinical utility. Deep learning can overcome these limitations, boosting radiographic and dosimetric quality critical for online adaptive radiotherapy (ART). We hypothesize adapted contrastive unpaired translation (CUT), a recent method for image-to-image translation of photographic images, can improve CBCT quality while reducing compute time, demonstrating utility for ART.

MATERIALS/METHODS

Same-day CBCT and quality assurance CT (QACT) images acquired from 79 patients receiving proton therapy for prostate cancer between 2019 and 2020 at a single institution were retrospectively collected. QACT images were acquired for quality assurance in accordance with institutional policy. Seventy-nine patients yielded 102 non-contrast CBCT-QACT image sets. Each QACT image was rigidly registered to the corresponding CBCT and resampled to 1 × 1 × 2 mm to establish uniform voxel size and spacing. CBCT images were randomly shuffled prior to input to the CUT model for unsupervised training and QACT-quality synthetic CT images were generated as outputs. We compared mean absolute error (MAE), structural similarity index measure (SSIM), and Fréchet inception distance (FID) against same-day QACT.

RESULTS

MAE, SSIM, and FID were compared for the CycleGAN and CUT data relative to input QACT and are reported as the mean across five-fold cross-validation ± standard error. CUT achieved superior performance in MAE (19.5 ± 3.9 HU vs. cycleGAN 47.1 ± 25.4) and FID (31.5 ± 6.6 vs cycleGAN 75.9 ± 41.3). MAE indicates pixel-level correspondence to QACT HU intensity values, making the synthetic outputs of CUT useful for dose calculations during ART. FID further demonstrates perceptual visual similarity. SSIM for CycleGAN (0.7 ± 0.2) and CUT (0.8 ± 0.0) were similar, indicating acceptable reproducibility of global structure. CUT was faster and lighter than CycleGAN. CycleGAN contained a total of 28,286,000 parameters; CUT contained 14,703,000, approximately half that of CycleGAN. As a result, CycleGAN computes on a single CT image slice over 0.33s while CUT requires just 0.18s.

CONCLUSION

The contrastive method investigated here was demonstrated to be faster and more accurate than CycleGAN, requiring fewer networks and parameters to achieve superior performance. We demonstrated anatomic boundary preservation and HU fidelity superior to cycleGAN while significantly reducing compute time. We plan to investigate the use of these synthetic CT images in automated segmentation prior to exploration of CUT in a prospective setting.

Association of Radiation Facility Volume with Overall Survival in Patients with Very High-Risk Prostate Cancer Treated with Radiation and Androgen Deprivation Therapy

PURPOSE/OBJECTIVE(S)

Studies suggest an association of treatment at high volume facilities with improved survival in cancer patients receiving surgery or radiation therapy. This association has not been studied in patients with very high-risk prostate cancer, who are treated using a multimodality approach that often requires specialized care with advanced diagnostic imaging, complex radiotherapeutic planning, and multidrug antiandrogen regimens. We used the National Cancer Database (NCDB) to study the association of radiation treatment facility volume (FV) with overall survival (OS).

MATERIALS/METHODS

We selected for patients with very high risk, localized prostate cancer by NCCN criteria (cT3b-T4, primary Gleason pattern 5, >4 cores with grade group 4-5, and/or 2-3 high risk features). We included patients who received hormone therapy with either external beam radiation to a dose of ≥60 Gy or external beam radiation to a dose of ≥45 Gy combined with brachytherapy. Association of FV with OS was evaluated through a bias-adjusted log-rank test to identify the optimal cut point of FV for dichotomization. Kaplan-Meier curves were used to study the association of binary FV with overall survival (OS) with and without IPTW (inverse probability treatment weighting) balancing the following confounders: age, race, median income, education, insurance, academic treatment facility, Charlson comorbidity score, T stage, PSA, Gleason score, total radiation dose, year of diagnosis, and patient distance from treatment facility. Cox proportional hazards model was built using backward variable selection strategy (α of 0.05 for removal).

RESULTS

We identified 25,219 very high-risk prostate cancer patients by NCCN criteria (median follow up 57.36 months; 95% CI 56.67 - 58.09) diagnosed between 2004 and 2015. High FV (n = 6,438) was associated with better OS on univariable analysis (hazard ratio [HR] = 0.81; 95% confidence interval [CI] 0.77 - 0.86; p < 0.001) and multivariable analysis (HR = 0.89; 95% CI 0.84 - 0.95; p < 0.001). Other factors associated with improved OS on multivariable analysis included younger age, non-white/black race, higher income, private insurance, academic/research treatment facility, lower comorbidity, lower T-stage, lower PSA, and lower Gleason score. After IPTW adjustment, high FV remained associated with better OS (HR = 0.90; 95% CI 0.85 - 0.95; p < 0.001).

CONCLUSION

Patients with NCCN very high-risk prostate cancer treated at a radiation facility with high case volume had better OS than patients treated at a facility with low volume, after adjustment for confounders. This may suggest that for very high-risk patients, outcomes may be improved by the expertise and optimal multidisciplinary care that typically accompany high facility treatment volume.

Prognostic Significance of Pretreatment Immune Cell Infiltration in Muscle Invasive Bladder Cancer Treated with Definitive Chemoradiation: Analysis of NRG RTOG 0524 and 0712

PURPOSE/OBJECTIVE(S)

Chemoradiation therapy (CRT) is an organ conserving approach in the treatment of locally advanced bladder cancer. Chemoradiation is thought to potentially result in immunogenic stimulation, and bladder cancer is often a tumor with high immune cell infiltration. Thus, we aimed to profile the tumor immune microenvironment of bladder cancer and identify prognostic immune biomarkers for CRT response by profiling tumor samples from NRG/RTOG 0524 and 0712, two prospective trials of CRT in muscle invasive bladder cancer (MIBC).

MATERIALS/METHODS

Pretreatment tissue samples from both trials were profiled using Cofactor Genomics ImmunoPrism, an RNA sequencing assay that uses gene expression profiles to quantify immune cell populations in the tumor microenvironment (TME). Differential gene expression was estimated for different immune cell type proportions across samples. Kaplan-Meier survival analysis and log rank tests were performed to evaluate differences in overall survival (OS) stratified by genes influenced by immune cell proportions or genes associated with immune response signatures.

RESULTS

A total of 70 samples (43 from RTOG 0524 and 27 from RTOG 0712) underwent analysis using the ImmunoPrism assay. Immune cell proportions were as follows: CD8 T cells: median 1.2%, CD4 T cells: median 0.8%, Treg cells: median 9.2%, CD19 B cells: median 5.1%, M2 macrophages: median 0.8%, M1 macrophages: median 0%. Unbiased clustering based on gene expression profiles driven by immune cell proportions demonstrated two groups: cluster 1 with a low percentage of immune cells and shorter OS (median 31 months) and cluster 2 with a high percentage of immune cells and longer OS (median 101 months, p = 0.036). Higher expression of genes associated with T cell infiltration (CD8A and ICOS) was associated with improved OS (104 vs 35 months, p = 0.028, HR = 0.48 (0.25 - 0.94), p = 0.031) as was higher expression of IDO1, which is associated with the interferon gamma pathway (104 vs 35 months, p = 0.042, HR = 0.49 (0.24 - 0.99), p = 0.046).

CONCLUSION

Bladder tumors have a wide range of immune cell infiltration in the TME. Increased immune cell proportions are prognostic for OS following CRT, as well as a higher expression of genes associated with T cell infiltration interferon gamma signaling. These findings have implications for the integration of immunotherapy in the definitive management of MIBC; and can be explored further in the ongoing NRG/SWOG 1806 trial.

Digital Image Encryption Using Double Crossover Approach for SARS-CoV-2 Infected Lungs in a Blockchain Framework

As the (Covid-19) pandemic spreads, the creativity of the scientific community is thriving while trying to control the situation. They are trying to treat patients viably and work with the almost exhausted medical equipment and staff, while growing new, successful antibodies. Successful screening of SARS-CoV-2 empowers fast and proficient determination of COVID-19 and can relieve the weight on medical care frameworks. Numerous forecast models are being created to comprehend and prognosticate the spread of the pandemic and to stay away from the following wave. But in the coming time, we can be sure that the models would experience the ill effects of a few issues, security being one of them. All the models need to be built in such a way that the investigation task gets successfully conducted without compromising the privacy and security of the patients. To take care of this, we propose a blockchain framework for sharing patients’ personal data or medical reports. A blockchain will take care of the integrity part, but we still need to worry about confidentiality. Therefore, combining a genetic approach with a blockchain seemed like a good idea. A twofold hybrid methodology is proposed in this paper to tackle the issue of confidentiality. The outcomes displayed high entropy accomplishment for the utilized dataset. The sensitivity of the plaintext and ciphertext is also checked and compared with existing approaches which thus demonstrates the security of the proposed approach in the given setting.

Asymmetric Confidentiality in Blockchain Embedded Smart Grids in Galois Field

Economic growth requires a sharp increase in the utilization of energy. Since the initial mechanical era, financial development has been driven by industrialization, transportation, and, most important of all, electrification, majorly achieved by petroleum product ignition. This way of development has had malicious and abusive aftershocks on the environment since the beginning. Smart grids are an idea to slightly diminish the burden on our Mother Nature, but this idea is getting tainted by the anticipation of ferocious technophiles who may try to get the grid down using quantum computers in the coming years. Thus, security becomes one of the major concerns for the smart grid. In this paper, we propose a quantum-resistant framework for associating smart grids and blockchain embedded with a permutation-substitution-based public-key cryptosystem in Galois Field to prevent unauthorized access and perform encryption of the private information of the user and consumption statistics. Permutation and substitution are performed to increase the diffusion and confusion of the data. Expenditures are quantified from the dissipation particulars, and the payment of electricity bill is performed using our blockchain wallet. The prediction model of consumption data is generated availing stochastic gradient descent. The performance analysis of the proposed cryptosystem is predicted after a simulation of the smart grid.

What is the value of digital health?

The panellist Anant Jani will discuss about: What is the value of digital health? There is much hope and hype surrounding the potentially transformative effect that digital health tools can have in health and care systems but it is very difficult to ascertain the true value that digital health tools currently deliver or could deliver in the future. Compounding this uncertainty is the diverse, large and ever-changing digital health landscape - there are currently over 300,000 health and care apps on the market place in comparison to the less than 2000 drugs health and care systems normally have to deal with. In this session, we highlight how the quadruple value framework, recently endorsed by the EU Commission, can be used to help rationalize the digital health ecosystem by promoting the interventions that have the greatest potential to promote primary, secondary or tertiary prevention while optimising resource utilisation.

Creating a common language: defining individualized, personalized and precision prevention in public health

Background

Because of the limited success of population-based prevention methods and due to developments in genomic screening, public health professionals and health policy makers are increasingly interested in more individualized prevention strategies. However, the terminology applied in this field is still ambiguous and thus has the potential to create misunderstandings.

Methods

A narrative literature review was conducted to identify how individualized, personalized and precision prevention are used in research papers and documents. Based on the findings a set of definitions were created that distinguish between these activities in a meaningful way.

Results

Definitions were found only for precision prevention, not for individualized or personalized prevention. The definitions of individualized, personalized and precision medicine were therefore used to create the definitions for their prevention counterparts. By these definitions, individualized prevention consists of all types of prevention that are individual-based; personalized prevention also consists of at least one form of -omic screening; and precision prevention further includes psychological, behavioral and socioeconomic data for each patient.

Conclusions

By defining these three key terms for different types of individual-based prevention both researchers and health policy makers can differentiate and use them in their proper context.

RADI-14. FRAMELESS STEREOTACTIC RADIOSURGERY ON THE GAMMA KNIFE ICON: EARLY EXPERIENCE FROM 42 PATIENTS WITH BRAIN METASTASES

BACKGROUND: The Gamma Knife (GK) Icon uses a Cone-Beam CT (CBCT) scanner and an infrared camera system to support the delivery of frameless radiosurgery. There are limited data on patients treated with frameless GK radiosurgery (GKRS) for brain metastases. OBJECTIVE: To describe the early experience, process, technical details, and short-term outcomes with frameless GKRS for brain metastases at our institution. METHODS: We describe our patient selection and workflow for frameless GKRS in detail. Because of the short interval of follow-up, we provide crude rates of local control. RESULTS: 42 patients had a total of 96 brain metastases. Median age was 69. 77 intact lesions were treated definitively, 18 cavities postoperatively, and 1 had GKRS for recurrence after resection. 11 patients underwent repeat GKRS to the same area. Median dose was 20Gy in 1 fraction (range: 14–21), 24Gy in 3 fractions (range: 19.5–27), and 25Gy in 5 fractions (Range: 25–30). Median treatment time was 23.7 minutes (Range: 7.3 – 85.5). 29 patients had a follow-up MRI in our records after completing GKRS. Median follow-up time was 105 days (Range: 16 – 314). 16 local recurrences (LR) were identified in 9 patients. An additional 6 patients had distant brain recurrence without LR. Crude mean time between GKRS and LR was 101 days (range 44–161 days). There were 6 patients with grade 1, 3 with grade 2, 2 with grade 3, and 1 with grade 4 toxicity. We found an improvement in workflow and a greater number of patients eligible for GKRS due to the ability to fractionate treatments. CONCLUSION: We report a large cohort of consecutive patients with brain metastases treated with frameless GKRS. We look forward to studies with longer follow-up to provide valuable data on clinical outcomes and to further our understanding of the radiobiology of hypofractionation in the brain.

Single institution validation of a modified graded prognostic assessment of patients with breast cancer brain metastases

Aim:

The number of breast cancer brain metastases is a prognostic clinical variable in the modified graded prognostic assessment (GPA) Index for breast cancer.

Patients & methods:

We retrospectively gathered data from 127 breast cancer patients who underwent radiation therapy for brain metastasis. Patients were stratified by both breast GPA and modified breast GPA scores, and survival was determined using the Kaplan–Meier curves and Cox proportional hazards model.

Results & Conclusion:

The Kaplan–Meier curve for patients under the breast GPA classification were not significant, but were significant under the modified breast GPA classification. The inclusion of number of brain metastases into the modified breast GPA index improved prognosis, thus validating the use of the modified breast GPA in prognosticating patient outcome.

Rectal balloon use limits vaginal displacement, rectal dose, and rectal toxicity in patients receiving IMRT for postoperative gynecological malignancies

Pelvic radiotherapy for gynecologic malignancies traditionally used a 4-field box technique. Later trials have shown the feasibility of using intensity-modulated radiotherapy (IMRT) instead. But vaginal movement between fractions is concerning when using IMRT due to greater conformality of the isodose curves to the target and the resulting possibility of missing the target while the vagina is displaced. In this study, we showed that the use of a rectal balloon during treatment can decrease vaginal displacement, limit rectal dose, and limit acute and late toxicities. Little is known regarding the use of a rectal balloon (RB) in treating patients with IMRT in the posthysterectomy setting. We hypothesize that the use of an RB during treatment can limit rectal dose and acute and long-term toxicities, as well as decrease vaginal cuff displacement between fractions. We performed a retrospective review of patients with gynecological malignancies who received postoperative IMRT with the use of an RB from January 1, 2012 to January 1, 2015. Rectal dose constraint was examined as per Radiation Therapy Oncology Group (RTOG) 1203 and 0418. Daily cone beam computed tomography (CT) was performed, and the average (avg) displacement, avg magnitude, and avg magnitude of vector were calculated. Toxicity was reported according to RTOG acute radiation morbidity scoring criteria. Acute toxicity was defined as less than 90 days from the end of radiation treatment. Late toxicity was defined as at least 90 days after completing radiation. Twenty-eight patients with postoperative IMRT with the use of an RB were examined and 23 treatment plans were reviewed. The avg rectal V40 was 39.3% ± 9.0%. V30 was65.1% ± 10.0%. V50 was 0%. Separate cone beam computed tomography (CBCT) images (n = 663) were reviewed. The avg displacement was as follows: superior 0.4 + 2.99 mm, left 0.23 ± 4.97 mm, and anterior 0.16 ± 5.18 mm. The avg magnitude of displacement was superior/inferior 2.22 ± 2.04 mm, laterally 3.41 ± 3.62 mm, and anterior/posterior 3.86 ± 3.45 mm. The avg vector magnitude was 6.60 ± 4.14 mm. For acute gastrointestinal (GI) toxicities, 50% experienced grade 1 toxicities and 18% grade 2 GI toxicities. For acute genitourinary (GU) toxicities, 21% had grade 1 and 18% had grade 2 toxicities. For late GU toxicities, 7% had grade 1 and 4% had grade 2 toxicities. RB for gynecological patients receiving IMRT in the postoperative setting can limit V40 rectal dose and vaginal displacement. Although V30 constraints were not met, patients had limited acute and late toxicities. Further studies are needed to validate these findings.

Risk of dry eye syndrome in patients treated with whole-brain radiotherapy

With improvements in systemic therapy, patients with cancer treated with whole-brain radiotherapy (WBRT) are living long enough to develop late toxicities, including dry eye syndrome. In general practice, dose to the lacrimal gland (LG) is not constrained (maximum constraint <40 Gy) in WBRT. The purpose of this study was to measure dose to the LG in WBRT and determine methods for reducing radiation exposure. We conducted a retrospective review of 70 3-dimensional (3D) conformal plans; thirty-six plans with a radiation prescription of 30 Gy in 10 fractions and 34 plans with a prescription of 37.5 Gy in 15 fractions. LGs were contoured in accordance with Freedman and Sidani (2015). Biological effective dose (BED)3 maximum constraints were calculated from 40 Gy and 20 Gy to be 32.17 Gy (30 Gy) and 36.70 Gy (37.5 Gy). Both regimens demonstrated supraorbital blocking by 3 methods: T1, bordering the supraorbital ridge; T2, no contact with supraorbital ridge; and T3, coverage of the supraorbital ridge. Mean dose for the plans with a 30-Gy prescription and the plans with a 37.5-Gy prescription was 27.5 Gy and 35.2 Gy, respectively (p ≤ 0.0001). BED3 maximum constraint (D_max) was violated 16 of 26 (61.5%) in T1 (average D_max: 32.2 Gy), 13 of 28 (46.4%) in T2 (average D_max: 32.1 Gy), and 5 of 18 (27.8%) in T3 (average D_max: 31.8 Gy) for the 30-Gy prescription. D_max was violated in 32 of 32 (100%) in T1 (average D_max: 40.1 Gy), 22 of 22 (100%) in T2 (average D_max: 40.3 Gy), and 14 of 14 (100%) in T3 (average D_max: 39.4) for the 37.5 Gy prescription. Average D_max for the 37.5-Gy prescription was highly significant in favor of T3 (p = 0.0098). Patients who receive WBRT may develop dry eye syndrome as a late toxicity. Constraints are commonly violated with a prescription of 37.5 Gy. Methods to reduce dose include T3 supraorbital blocking, an easily implementable change that may dramatically improve patient quality of life.

Breast cancer subtype and stage are prognostic of time from breast cancer diagnosis to brain metastasis development

Breast cancer brain metastasis (BCBM) is associated with high morbidity and mortality. Patients with breast cancer risk factors associated with rapid development of BCBM could potentially benefit from early brain metastasis screening. We retrospectively reviewed all BCBM patients treated with brain radiotherapy at our institution from 1997 to 2015. Interval time to BCBM was defined as date of pathologic breast cancer diagnosis to date of radiographic evidence of brain metastasis. Patients were stratified by breast cancer molecular subtype and stage at diagnosis. Kaplan Meier analysis was conducted on time to development of BCBM. Breast cancer risk factors were correlated with time to BCBM on Cox proportion hazard analysis. The study cohort comprised 121 BCBM patients, with median interval time to BCBM of 46 months. Times to BCBM for Her2+/2HR+, Her2+, Her2-/HR+, and triple-negative (TNBC) subtypes were 70, 44, 42, and 28 months respectively (p = 0.002). Time to BCBM for stages I, II, III, and IV were 70, 54, 29, and 24 months, respectively (p = 0.000). BCBM patients were further stratified by both molecular subtype (TNBC vs. non-TNBC) and stage (I, II vs. III, IV). Median times to BCBM for non-TNBC/stage I-II, TNBC/stage I-II, non-TNBC stage III-IV, and TNBC/stage III-IV were 68, 47, 29, and 6 months respectively (p = 0.000). Subtype and stage were associated with shorter time to BCBM on multivariate analysis. Subtype and initial stage are independently correlated with decreased time to development of BCBM. Patients with advanced high stage and triple negative breast cancer develop brain metastases significantly earlier.

Whole-brain Irradiation Field Design: A Comparison of Parotid Dose

Whole-brain radiation therapy (WBRT) plays an important role in patients with diffusely metastatic intracranial disease. Whether the extent of the radiation field design to C1 or C2 affects parotid dose and risk for developing xerostomia is unknown. The goal of this study is to examine the parotid dose based off of the inferior extent of WBRT field to either C1 or C2. Patients treated with WBRT with either 30 Gy or 37.5 Gy from 2011 to 2014 at a single institution were examined. Parotid dose constraints were compared with Radiation Therapy Oncology Group (RTOG) 0615 nasopharyngeal carcinoma for a 33-fraction treatment: mean <26 Gy, volume constraint at 20 Gy (V20) < 20 cc, and dose at 50% of the parotid volume (D50) < 30 Gy. Biologically effective dose (BED) conversions with an α/β of 3 for normal parotid were performed to compare with 10-fraction and 15-fraction treatments of WBRT. The constraints are as follows: mean < BED 32.83 Gy, V15.76 (for 10-fraction WBRT) or V17.35 (for 15-fraction WBRT) < 20 cc, and D50 < BED 39.09 Gy. Nineteen patients treated to C1 and 26 patients treated to C2 were analyzed. Comparing WBRT to C1 with WBRT to C2, the mean left, right, and both parotids' doses were lower when treated to C1. Converting mean dose to BED₃, the parotid doses were lower than BED₃ constraint of 32.83 Gy: left (30.12 Gy), right (30.69 Gy), and both parotids (30.32 Gy). V20 to combined parotids was lower in patients treated to C1. When accounting for fractionation of WBRT received, the mean corrected V20 volume was less than 20 cc when treating to C1. D50 for C1 was lower than C2 for the left parotid, right parotid, and both parotids. BED₃ conversion for the mean D50 of the left, right, and both parotids was less than 39.09 Gy. In conclusion, WBRT to C1 limits parotid dose, and parotid dose constraints are achievable compared with inferior border at C2. A possible mean parotid dose constraint with BED₃ should be less than 32.83 Gy.

Stereotactic body radiotherapy for pancreatic cancer: Analysis of toxicity

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Background: Pancreatic ductal adenocarcinoma (PDAC) carries a poor prognosis, with significant morbidity and mortality from local progression. Radiotherapy can be administered for local control, with stereotactic body radiotherapy (SBRT) increasingly being utilized. We aim to compare the toxicity of SBRT with intensity-modulated radiotherapy (IMRT) in this setting. Methods: A retrospective analysis of patients with PDAC receiving IMRT or SBRT at our institution between April 2011 and November 2015 was performed. 81 patients were identified. Clinical notes were reviewed for treatment details and acute and late toxicities. Late toxicity data was available for 62 patients. Toxicity was assessed using Common Terminology Criteria for Adverse Events version 4.0. Radiology reports were reviewed to assess for the presence of recurrence and/or progression. Results: Median follow-up from RT was 29 months (95% CI 22-36 months), and median survival from RT was 25 months (95% CI 22-34 months). IMRT patients received 37.5-54 Gy in 15-30 fractions. SRBT patients received 19.8-39.6 Gy in 3-6 fractions. 45% of IMRT and 29% of SBRT patients had local failure (p = 0.1329). IMRT patients were significantly more likely to have Grade ≥2 acute gastrointestinal (GI) toxicity than SBRT patients (RR 1.70; 95% CI 0.98-2.96, p = 0.0489), although one SBRT patient had to have treatment stopped due to extrahepatic stricture. There were no significant differences in late GI toxicity (67% Grade 2 or higher vs. 57%, respectively, p = 0.4244), although one IMRT patient died due to late GI bleeding.IMRT patients were more likely to lose weight during RT(Median -0.03% vs. -0.004%, p = 0.0001) and have moreEmergency Department (ED) visits after RT (Range 0-8 vs. 0-3, p = 0.0019). There were no significant differences in dermatitis, fatigue, or hematologic toxicity. Conclusions: Patients with locally advanced PDAC treated with IMRT versus SBRT had significantly more acute gastrointestinal toxicity, median weight loss, and ED visits after RT, but no significant differences in late gastrointestinal toxicity, dermatitis, fatigue, or hematologic toxicity. SBRT is a relatively tolerable and more convenient alternative for patients with pancreatic cancer.

Timing of Adjuvant Radiotherapy in Glioblastoma Patients: A Single-Institution Experience With More Than 400 Patients

BACKGROUND

The standard of care for patients with newly diagnosed glioblastoma (GBM) is maximal safe resection followed by adjuvant radiation therapy (RT) and temozolomide (TMZ).

OBJECTIVE

To investigate whether the timing of adjuvant RT after surgery affected outcome in patients with GBM.

METHODS

We retrospectively reviewed all patients with a diagnosis of GBM at our institution. A total of 447 patients were included in our analysis. Patients were divided into 3 equal groups based on the interval between surgery and RT. The primary outcome was overall survival (OS).

RESULTS

Patients who began RT less than 21 days after surgery tended to be older, have a lower a Karnofsky Performance Status score, and higher recursive partitioning analysis class. These patients were more likely to have undergone biopsy only and received 3-dimensional conformal RT or 2-dimensional RT. The median OS for patients who started RT less than 21 days after surgery, between 21 and 32 days after surgery, and more than 32 days after surgery was 374, 465, and 478 days, respectively (P = .004). On multivariate Cox regression analysis, Karnofsky Performance Status score lower than 70, undergoing biopsy only, recursive partitioning analysis classes IV and V/VI, use of less than 36 Gy RT, and lack of TMZ chemotherapy were predictors of worse OS. The interval between surgery and RT was not significantly associated with OS on multivariate analysis.

CONCLUSION

Patients who begin RT less than 21 days after surgery tend to have worse prognostic factors than those who begin RT later. When accounting for significant covariates, the effect of timing between surgery and RT is not significant.