ABSTRACT Introduction Sexual health problems affect approximately 60% of male cancer survivors in the U.S. Erectile dysfunction (ED) is the most common sexual health condition men seek professional help for after cancer treatment with some studies reporting ED rates as high as 85% in these men. Inflatable penile prosthesis (IPP) implantation is a safe and highly effective form of ED treatment for patients who fail or cannot tolerate medical therapies. A 2011 study suggested that IPPs are under-utilized by urologists, as less than 1% of men with prostate cancer and ED received IPP following radical prostatectomy or external beam radiation. Objective To better characterize the utilization of IPP treatment, we examined the relationships between ED, prostate cancer treatment type and IPP implantation in a national cohort. Methods We performed a retrospective review of older SEER-Medicare patients who were diagnosed with local/regional prostate cancer between 2006 and 2011 and treated with surgery or radiation for it, with and without ED. Using ICD9/CPT/HCPCS codes we created a cohort of patients who has receipt of surgery or radiation within 3 months of cancer diagnosis as well as diagnosed ED within 5-years after undergoing treatment. Chi-square/Wilcoxon tests were used to detect significant differences between the surgical and radiation treatment groups for ED rates and use of IPP among those with ED. Results Of the 31,854 patients in our cohort, 10,475 (32.9%) received surgery and 21,152 (66.4%) received radiation only. Overall, ED was significantly more common for surgical (65.2%) than for radiation patients (33.8%, p<.001). For the subset of 14,121 patients with ED (overall IPP use=2.5%), IPP implantation was significantly more frequent for surgical patients (n=6,976, IPP use= 3.6%) than for radiation patients (n=7,145, IPP use=1.4%, p<.001). Conclusions Shockingly few (2.5%) prostate cancer patients with ED received IPP, with only 1.4% of radiation patients undergoing IPP vs. 3.6% of RALP patients. IPP under-utilization may be due to greater clinical focus on cancer treatment rather than quality-of-life issues. Discrepancies in ED rates between radiation and surgery may also be partially explained by lack of follow-up standardization and highly variable sexual dysfunction reporting, especially in the radiation literature. These findings highlight the importance of thorough counseling about all treatment options including penile prosthesis surgery for prostate cancer patients with ED. Disclosure No

ABSTRACT Introduction Penile Prosthesis (IPP) is an effective treatment for men with ED that significantly improves quality of life but is likely being underutilized in men who were treated for prostate cancer (Pca). Objective To better characterize the utilization of IPP treatment after Pca therapy, we explored the relationship between timing of ED diagnosis (before vs after treatment), treatment modality (radiation vs. prostatectomy), and various sociodemographic factors in a national cohort. Methods We performed a retrospective review of SEER-Medicare patients who were diagnosed with local/regional Pca between 2006 and 2011.Using ICD9/CPT/HCPCS codes, we created a subset of patients who were diagnosed with ED 12 months prior to their Pca treatment, until 5 years after. Chi-square/Wilcoxon tests were used to detect significant differences between the use of IPP among those with ED prior to Pca treatment compared to after. In addition, various sociodemographic factors were examined. Results Of the 31,854 patients in our cohort, 14,482 (45.5%) were diagnosed with ED within 12 months prior to Pca diagnosis or 5 years after diagnosis. Among those diagnosed with ED prior to treatment (4366, 30.1%), 119 (2.7%) received IPP while among the 10,116 patients (69.9%) with ED diagnosis after treatment, 232 (2.3%) received IPP. Among patients with ED, factors decreasing the likelihood of receiving an IPP were diagnosis of ED prior to Pca treatment (OR=1.33, 95% CI: 1.06-1.66), relationship status of single (OR=1.88, 95% CI: 1.28-2.77) or divorced/separated (OR=2.13, 95% CI: 1.46-3.10), and identifying as Non-Hispanic Black (OR=1.72, 95% CI:1.24-2.37) or Hispanic (OR=1.81, 95% CI: 1.22-2.67) as compared to Non-Hispanic White men. Factors decreasing the likelihood of receiving an IPP were being treated with radiation therapy as opposed to prostatectomy (OR=0.38, 95% CI: 0.29-0.49), and increased age (OR=0.75 95% CI: 0.63-0.88). Conclusions Although more men have their ED treated with an IPP if they received their diagnosis prior to Pca treatment (2.7% vs. 2.3%), IPPs appear to be underutilized in all patients with ED after Pca therapy. This data suggests that factors (i.e. prior ED diagnosis, being single, Black or Hispanic) outside of the typically accepted medical indications may influence IPP selection as a treatment option for ED. Conversely, counseling pertaining to IPP surgery after Pca treatment may be lacking in men with newly diagnosed ED, married men, white men, older men, and men who received radiation therapy. More thorough evaluation of these demographic factors is warranted. Disclosure No

ESTRO 36 _______________________________________________________________________________________________ 70.2% infratentorial, the tumor grade was anaplastic in 62.0%, the extent of resection was complete in 85.1% and 64.5% of patients received a dose >54 Gy.The median PRTV was 43.8 cc (1.1-287.9),and the median CEPTV was 13.3 cc (0-71.4).The median PRTVF was 49.4 cc (0-336.7)and the median POTVF was 4.6 cc (0-118.7).A statistically significant benefit in survival was seen with a POTVF equal to 0 cc in univariate analysis for the DFS and the OS (71.9% versus 40.3% p=0.006) and (93.7% versus 72.37% p=0.023) respectively.In multivariate analysis, POTVF was also statistically significant for OS (p=0.05) and almost significant for DFS (p=0.06). ConclusionIn this retrospective study, POTVF was found to be significant predictor of overall survival after ependymoma radiotherapy.POTVF was the more significant predictor of survival compared with PRTV, suggesting that this volume and residual contrast-enhancing tumor may be a more accurate and meaningful reflection of the pathobiology of ependymoma.

Purpose: Use a NEMA-IEC PET phantom to assess the robustness of FDG-PET-based radiomics features to changes in reconstruction parameters across different scanners. Methods: We scanned a NEMA-IEC PET phantom on 3 different scanners (GE Discovery VCT, GE Discovery 710, and Siemens mCT) using a FDG source-to-background ratio of 10:1. Images were retrospectively reconstructed using different iterations (2–3), subsets (21–24), Gaussian filter widths (2, 4, 6mm), and matrix sizes (128,192,256). The 710 and mCT used time-of-flight and point-spread-functions in reconstruction. The axial-image through the center of the 6 active spheres was used for analysis. A region-of-interest containing all spheres was able to simulate a heterogeneous lesion due to partial volume effects. Maximum voxel deviations from all retrospectively reconstructed images (18 per scanner) was compared to our standard clinical protocol. PET Images from 195 non-small cell lung cancer patients were used to compare feature variation. The ratio of a feature's standard deviation from the patient cohort versus the phantom images was calculated to assess for feature robustness. Results: Across all images, the percentage of voxels differing by <1SUV and <2SUV ranged from 61–92% and 88–99%, respectively. Voxel-voxel similarity decreased when using higher resolution image matrices (192/256 versus 128) and was comparable across scanners. Taking the ratio of patient and phantom feature standard deviation was able to identify features that were not robust to changes in reconstruction parameters (e.g. co-occurrence correlation). Metrics found to be reasonably robust (standard deviation ratios > 3) were observed for routinely used SUV metrics (e.g. SUVmean and SUVmax) as well as some radiomics features (e.g. co-occurrence contrast, co-occurrence energy, standard deviation, and uniformity). Similar standard deviation ratios were observed across scanners. Conclusions: Our method enabled a comparison of feature variability across scanners and was able to identify features that were not robust to changes in reconstruction parameters.

To estimate the correlation between different dosimetric indices of the contralateral parotid and submandibular glands with the patient reported severity of dry mouth 6 months post de-intensified chemoradiation therapy. Forty-three patients were treated on a prospective multi-institutional phase II study (ClinicalTrials.gov, NCT01530997) assessing the efficacy of de-intensified chemoradiation therapy in patients with favorable risk, HPV-associated oropharyngeal squamous cell carcinoma. All patients received 60 Gy intensity modulated radiation therapy with concurrent weekly intravenous cisplatinum (30 mg/m2). The protocol specified dosimetric goals for the contralateral parotid and submandibular glands were mean dose < 26 and < 35, respectively. All patients reported severity of their dry mouth (pre- and post-treatment) using the patient reported outcome version of the CTCAE (PRO-CTCAE): i.e. none/mild/moderate/severe/very severe. We correlated individual patient dosimetric data (e.g. Dmean and various Vxs) from the contralateral parotid and submandibular glands (separate and combined) to changes in their self-reported PRO-CTCA severity of dry mouth (baseline to 6 month post-treatment). A change in severity (from baseline) of >/= 2 was considered clinically meaningful. The ability of different dosimetric indices to accurately predict for patient outcomes was assessed through the area under to Receiver Operating Characteristic curve (ROC) and odds ratios (OR). The combined contralateral glands (parotid and submandibular) had better AUC values than the individual glands. For the combined glands, various Vx values (ranging from V16-V38) and the mean dose had the highest AUC’s (80% to 83%). Among these, the optimal predictor appears to be V18 with an AUC of 83%, threshold of 57%, and hazard ratio of 5.1 (95% CI of 1.3-20.2). For the contralateral parotid V18 to V22 had the highest AUC’s (78% to 79%) and the Dmean was not as strong a predictor (AUC 76%, threshold of 23Gy). Vxs of V27 to V36 (AUCs 78% to 79%) of the contralateral submandibular glands were better predictors of xerostomia than Dmean (AUC 71%). The standard dosimetric objectives of mean dose < 26 Gy for the contralateral parotid and < 35 Gy for the contralateral submandibular gland may not be the optimal indices for sparing salivary gland function in patients with HPV-associated oropharyngeal cancer who receive de-intensified chemoradiation therapy. The rate of patient reported xerostomia following de-intensified chemoradiation therapy appears to be best correlated with the V18 of the combined contralateral parotid and submandibular glands.