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Brain metastases traditionally carried a poor prognosis with an overall survival of weeks to months in the absence of treatment. Radiation therapy modalities include whole brain radiation therapy (WBRT) and stereotactic radiosurgery (SRS). WBRT delivers a relatively low dose of radiation, has neurocognitive sequelae, and has not been investigated for its immunostimulatory effects. Furthermore, WBRT exposes the entire intracranial tumor immune microenvironment to radiation. SRS delivers a high dose of conformal radiation with image guidance to minimize dose to surrounding normal brain tissue, and appears to promote anti-tumor immunity. In parallel with many of these discoveries, immune checkpoint inhibitors (ICIs) have demonstrated a survival advantage in multiple malignancies commonly associated with brain metastases (e.g., melanoma). Combination SRS and ICI are theorized to be synergistic in anti-tumor immunity directed to brain metastases. The purpose of this review is to explore the synergy of SRS and ICIs, including pre-clinical data, existing clinical data, and ongoing prospective trials.

182 Background: The purpose of this study was to examine the associations of three different measures of anxiety and depression with patient reported distress (PRD) level and survival after radiotherapy (RT). Methods: 518 patients who underwent RT between 2012 and 2016 were included in this retrospective study. PRD was assessed at the time of RT using the NCCN thermometer and a 30 question survey of distress related items. PRD and clinical and demographic data was retrospectively collected and analyzed. The three measures this study focused on that assessed patient anxiety and depression involved asking patients about their level of concern regarding feeling down, regarding loss of interest, and regarding feeling nervous. Associations between baseline patient characteristics and survival after start of RT were evaluated using single variable Cox proportional hazards regression models. Hazard ratios (HRs) and 95% confidence intervals (CIs) were estimated. Associations of level of concern regarding patient anxiety/depression with survival after RT were evaluated using single variable and multivariable Cox proportional hazards regression models. Results: Overall, PRD level and concern regarding anxiety/depression were positively correlated (p < 0.001). Additionally, there was a significant association between level of concern regarding feeling down and palliative patients (p = 0.03). There was also a significant association between level of concern regarding loss of interest and palliative patients (p = 0.03), with level of concern highest for thorax, breast, and head and neck. There was also a significant different between level of concern regarding feeling nervous and gender (p = 0.05). There was not a significant difference between any of the three measures and survival after RT (all p ≥ 0.21). Conclusions: Anxiety and depression in patients receiving palliative and curative RT was associated with overall distress. Baseline screening of PRD may identify patients who would benefit from intervention to address the causes of their underlying anxiety and depression.

Objective: High GATA2 expression has been associated with an increased risk of poor clinical outcomes after radical prostatectomy; however, this has not been studied in relation to risk of biochemical recurrence (BCR) after salvage radiation therapy (SRT) for recurrent prostate cancer after radical prostatectomy. Our aim was to evaluate the association between protein expression levels of GATA2 in primary prostate cancer tumour samples and the risk of BCR after SRT. Methods: 109 males who were treated with SRT were included. The percentage of cells with nuclear staining and GATA2 staining intensity were both measured. These two measures were multiplied together to obtain a GATA2 H-score (range 0–12) which was our primary GATA2 staining measure. Results: In unadjusted analysis, the risk of BCR was higher for patients with a GATA2 H-score &gt;4 (hazard ratio = 2.04, p = 0.033). In multivariable analysis adjusting for SRT dose, pre-SRT PSA, pathological tumour stage and Gleason score, this association weakened substantially (hazard ratio = 1.45, p = 0.31). This lack of an independent association with BCR appears to be the result of correlations between GATA2 H-score &gt;4 and higher pre-SRT PSA (p = 0.021), higher Gleason score (p = 0.044) and more severe pathological tumour stage (p = 0.068). Conclusion: Higher levels of GATA2 expression appear to be a marker of prostate cancer severity; however, these do not provide independent prognostic information regarding BCR beyond that of validated clinicopathological risk factors. Advances in knowledge: A higher GATA2 expression level appears to be correlated with known measures of prostate cancer severity and therefore is likely not an independent marker of outcome after SRT.

764 Background: Psychosocial distress screening and assessment in patients with gastrointestinal (GI) cancers has an established importance due to the distress experienced during and post treatment. GI cancer patients receiving radiotherapy (RT) for curative or palliative measures were reviewed in order to determine if there was a relationship between patient reported distress (PRD) and survival. Methods: Patients at our institution who receive external beam RT for GI cancers completed a 30 question PRD survey that also included a linear analog measure of overall distress, the National Comprehensive Cancer Network (NCCN) Distress Thermometer, which ranged from 1 (low overall distress) to 10 (high overall stress) at the start of and/or during treatment. Each question on the PRD questionnaire concentrated on a possible cause of distress. It allowed patients to rate distress levels for each question from 1 to 5 (1 being the least distressed and 5 being the most distressed), and also overall distress according. The reported clinical results of the PRD questionnaire were retrospectively reviewed in patients receiving RT for GI cancers from Jan 2012 to Aug 2015. Patients were considered distressed if their overall PRD score was 5 or greater (PRD+) or not distressed (PRD-) if their score was 4 or under. Overall survival between PRD+ and PRD- was compared using the Kaplan-Meier method. Results: PRD surveys were completed by 134 consecutive patients, 67 (50%) male and 67 (50%) female within 30 days of starting RT. The median age was 65 years (range 28 to 93). The top histological finding was adenocarcinoma, 90 patients (60%). 113 (84%) received chemotherapy and 64 (48%) underwent surgery. 102 (75%) treatments were curative and 32 (25%) were palliative. Overall NCCN distress thermometer results ranged from 0 to 10, with a median of 4. Median follow-up was 2.7 years. Distressed patients (PRD+) had inferior survival to those not distressed (PRD-) at 2 years, 52% vs. 72%, p<0.02. Conclusions: Patient reported distress is associated with an inferior survival in patients receiving radiotherapy for gastrointestinal tumors.

The purpose of this study was to introduce a planning strategy for dynamic conformal arc therapy (DCAT), named negative margin technique (NMT), and evaluate its dosimetric gain in lung stereotactic body radiation therapy (SBRT). In DCAT, the field aperture is continuously conformed to the planning target volume (PTV) with an aperture margin (AM) to compensate for the penumbra effect with gantry rotation. It is a common belief the AM should be positive (or at least ‘zero'). However, the radial penumbra width becomes significantly wider because of continuously overlapped beams in arc delivery. Therefore, we hypothesize if the ‘negative margin’ is applied in the radial direction, it would improve the PTV dose conformation while reducing normal tissue dose. For verification, trial plans were made using the NMT and compared with ‘zero margin (ZM)’ plans for five lung SBRT cases representing different situations depending on the location of the PTV and organs at risk. All plans met 95% PTV coverage with the prescription dose and spared the spinal cord below the tolerance. Two conventional conformation indices (the ratio of prescription isodose volume to the PTV (CI100) and the ratio of 50% prescription isodose volume to the PTV (CI50)) and a modified conformation index were investigated. The maximum dose at 2 cm from the PTV and the percent of lung volume receiving 20 Gy were also evaluated. Another planning simulation was performed with a total of ten randomly selected lung SBRT cases to mimic actual practice. In this simulation, optimization with ZM was first performed and further optimization using the NMT was processed for cases that could not meet a goal of with the ZM optimization. In all cases, both the and values were significantly reduced (overall, and for and , respectively). The modified conformation index values also showed similar improvement (overall, increase). Reduction of was also observed in all cases . values decreased in all cases but one (, excluding the increased case). In the random group simulation, it was possible to achieve the goal with just one NMT trial for five out of six cases that did not meet the goal in the ZM optimization. Interestingly, however, one case needed as many as six iterations to get the goal. The NMT turned out to be an effective planning strategy that could bring significant improvement of dose conformation. The NMT can be easily implemented in most clinics with no prerequisite.PACS number: 87.55.D‐

211 Background: The current standard of care for locally advanced esophageal cancer includes chemoradiotherapy with or without surgery. Radiation is usually delivered via a 3D technique. IMRT has been utilized in the treatment of multiple tumors and demonstrated similar efficacy while offering the possibility of decreased toxicity. Methods: Thirty-six patients were treated with IMRT and chemotherapy. Twenty-one patients underwent surgical resection. Eleven underwent open surgery and the remainder underwent minimally invasive surgery. Chemotherapy consisted primarily of 5-FU with oxaliplatin or cisplatin. All but two patients received 50.4 Gy; one patient received 41.4 Gy without surgery and one patient discontinued treatment after 25.2 Gy. Eleven patients required a treatment break during radiotherapy. The median age was 69 (range 46-87). Approximately two-thirds of tumors were adenocarcinomas located in the lower thorax. Two thirds of patients were staged as T3 and had positive lymph nodes. The median tumor size was 5 cm (range 2-13). Results: With a median follow-up of 21.3 months (range 2.4-44.8) and 33.9 months for survivors (range 3.7-44.8), overall survival at 24 months was 55%. The 24 month overall survival was 75% vs 24% for surgical and non-surgical patients, respectively. Seven patients had a complete pathologic response. Twenty-four patients experienced grade 3 or higher acute toxicity and there was one grade 5 toxicity. Acute toxicity was similar between surgery and non-surgery patients. Fourteen patients experienced grade 3 or higher late toxicity; 9 surgery and 5 non-surgery patients. The most frequent late toxicity was grade 3 stricture (21%). On multivariate analysis, advanced age (RR [10 year increase] 2.01, p=0.032) and heart maximum dose >55 Gy (RR 3.73, p=0.011) were associated with decreased survival. Conclusions: Patients who undergo surgery after chemoradiotherapy demonstrate improved survival; however, this may be related to underlying comorbidities that preclude surgery. IMRT appears to be a reasonable treatment option that may reduce complications from radiotherapy. Careful attention should be given to heart dose during treatment planning.