D.T. Chang

Stereotactic body radiation for pancreatic cancer: results of an international survey of practice patterns

ObjectiveStereotactic body radiotherapy (SBRT) is an emerging treatment option for borderline resectable and locally advanced, unresectable pancreatic cancer (PCA). However, no standardized guidelines for treatment exist and patterns of SBRT use for PCA are unclear.MethodsRadiation oncologists known to use SBRT in the setting of PCA were invited to complete a 26-item Web-based survey on practice patterns.ResultsThirty of the 36 (83xa0%) invited radiation oncologists completed the survey. Of the responders, 86xa0% treat with 6–8xa0Gy ×5 fractions. The majority (93xa0%) of responders use four-dimensional computed tomography (4D-CT) for simulation, with 50xa0% using gating for breathing motion. Two thirds of radiation oncologists use fiducials for tumor localization. Most (79xa0%) responders noted an improvement in patient-reported pain after SBRT. Approximately, 59xa0% report difficulty obtaining insurance clearance for pancreas SBRT in the absence of a clinical trial. The largest variations in practice were related to gross tumor volume (GTV) to planning target volume (PTV) expansions and management of respiratory motion.ConclusionsSBRT is increasingly used for PCA. The data presented here indicate that the majority of radiation oncologists treat with 6–8xa0Gy ×5 fractions and use fiducials with 4D-CT simulation for localization and planning. Although the majority of the surveyed physicians prefer SBRT to standard radiation, it may be underutilized due to the difficulty of obtaining insurance approval outside of a clinical trial. Our investigation documents current pancreas SBRT practice patterns and highlights the need for prospective clinical trials as a means to develop consensus guidelines for this emerging treatment.

TU‐CD‐BRB‐08: Radiomic Analysis of FDG‐PET Identifies Novel Prognostic Imaging Biomarkers in Locally Advanced Pancreatic Cancer Patients Treated with SBRT

Purpose: This study aims to identify novel prognostic imaging biomarkers in locally advanced pancreatic cancer (LAPC) using quantitative, high-throughput image analysis. Methods: 86 patients with LAPC receiving chemotherapy followed by SBRT were retrospectively studied. All patients had a baseline FDG-PET scan prior to SBRT. For each patient, we extracted 435 PET imaging features of five types: statistical, morphological, textural, histogram, and wavelet. These features went through redundancy checks, robustness analysis, as well as a prescreening process based on their concordance indices with respect to the relevant outcomes. We then performed principle component analysis on the remaining features (number ranged from 10 to 16), and fitted a Cox proportional hazard regression model using the first 3 principle components. Kaplan-Meier analysis was used to assess the ability to distinguish high versus low-risk patients separated by median predicted survival. To avoid overfitting, all evaluations were based on leave-one-out cross validation (LOOCV), in which each holdout patient was assigned to a risk group according to the model obtained from a separate training set. Results: For predicting overall survival (OS), the most dominant imaging features were wavelet coefficients. There was a statistically significant difference in OS between patients with predicted high and low-risk based on LOOCV (hazard ratio: 2.26, p<0.001). Similar imaging features were also strongly associated with local progression-free survival (LPFS) (hazard ratio: 1.53, p=0.026) on LOOCV. In comparison, neither SUVmax nor TLG was associated with LPFS (p=0.103, p=0.433) (Table 1). Results for progression-free survival and distant progression-free survival showed similar trends. Conclusion: Radiomic analysis identified novel imaging features that showed improved prognostic value over conventional methods. These features characterize the degree of intra-tumor heterogeneity reflected on FDG-PET images, and their biological underpinnings warrant further investigation. If validated in large, prospective cohorts, this method could be used to stratify patients based on individualized risk.

Fractionation of palliative radiotherapy in metastatic breast cancer: Selection and survival.

201 Background: Various schedules of palliative radiotherapy (pRT) are prescribed for metastatic breast cancer (MBC) patients. Length of treatment can vary from a single day to three weeks. Single fraction pRT provides similar pain relief vs. multi-fraction pRT for bone metastases, but retreatment rates are higher. In the era of targeted and hormonal therapy, patients with MBC can survive many years after their initial diagnosis. We investigated whether patients with MBC who were prescribed single fraction pRT had poorer prognoses and experienced shorter survival than patients who were prescribed multi-fraction pRT.nnnMETHODSnPatients at a single institution with MBC underwent pRT, with fractionation schedules including 8 Gy in 1 fraction (fx), 20 Gy in 5 fx, 30 Gy in 10 fx, 37.5 Gy in 15 fx between 2001-2015. 392 treatments were prescribed (109/241/29/13 in each regimen as above). Date of death was obtained from medical records, Social Security Death Index, or published obituaries. Patients who were alive or whose date of death could not be determined were censored at the date of their last encounter. Survival was calculated from the start of treatment to the date of death or censorship.nnnRESULTSnPatients treated with 37.5 Gy in 15 fx (MS 20 months, p = 0.002) or 30 Gy in 10 fx (MS 22 months, p = 0.03) experienced longer survival than patients treated with 8 Gy in 1 fx (MS 8 months). There was no significant survival difference between patients treated with 20 Gy in 5 fx (MS 18 months, p = 0.49) and patients treated with 8 Gy in 1 fx. There was no significant survival difference between patients treated by the three multi-fractionation schedules.nnnCONCLUSIONSnMBC patients who were prescribed 37.5 Gy and 30 Gy lived longer than patients who were prescribed 8 Gy of pRT. No statistically significant difference was found between patients who were prescribed 20 Gy compared to 8 Gy, possibly due to the lower number of patients who received these regimens. Single fraction pRT was more likely to be prescribed to patients who would ultimately have shorter survival. More research is needed, ideally across multiple institutions, to explore the correlation between physician estimation of patient survival and selection of pRT regimen for patients with MBC.

Survival comparison of patients treated with one versus five fraction palliative radiotherapy.

200 Background: Choice of fractionation scheme for palliative radiotherapy has received greater attention in recent years, particularly in the current healthcare environment where issues of cost and quality of life have taken on increasing importance. The ASTRO Choosing Wisely campaign recommends against routine use of extended fractionation schemes ( > 10 fractions) for palliation of bone metastases given equivalent pain relief between 30 Gy in 10 fractions and 8 Gy in 1 fraction, and strong consideration for use of 8 Gy in 1 fraction is urged for patients with a limited prognosis or transportation difficulties. We investigated whether there was a difference in survival between patients treated with an intermediate fractionation scheme (5 fractions) and patients who received single-fraction treatment.nnnMETHODSnWe identified 220 patients who received a total of 264 courses of palliative radiotherapy with either 8 Gy in 1 fraction (n = 91) or 20 Gy in 5 fractions (n = 173). Date of death was obtained from either the patients medical record, the Social Security Death Index, or publicly available obituaries. If none of these yielded a date of death, patients were censored at the date of their last clinical encounter. The majority of patients (n = 192) were treated for bone metastases. All primary sites were included, with the three most common histologies being lung, breast and prostate (n = 80, 31 and 16, respectively).nnnRESULTSnOverall, we found no significant survival difference between the two groups. Patients treated with 8 Gy in 1 fraction had a median survival of 146 days, whereas patients treated with 20 Gy in 5 fractions had a median survival of 183 days (p = 0.43).nnnCONCLUSIONSnGiven no difference in survival between fractionation schemes of 20 Gy in 5 fractions and 8 Gy in 1 fraction, delivery of palliative radiation in a single fraction should be strongly considered. Previous studies have identified a higher re-treatment rate in single-fraction treatments, although closer analysis of this data revealed no difference in absolute pain scores prior to re-treatment. Thus, re-treatment for single-fraction radiotherapy may be due instead to a greater clinical willingness to re-treat as opposed to a greater clinical need.

Effects of gemcitabine and stereotactic body radiotherapy on quality of life in locally advanced pancreatic cancer.

278 Background: Existing literature on the impact of radiation therapy for locally advanced pancreatic cancer (LAPC) on quality of life (QoL) is limited and is specific to standard chemoradiation. We prospectively investigated patient-reported QoL after treatment with fractionated stereotactic body radiation therapy (SBRT). Methods: Forty-nine patients with LAPC treated were prospectively enrolled in a clinical trial at 3 institutions. Participants received a total of 33 Gy in 6.6 Gy daily fractions using SBRT either upfront (N=5) or after a single induction cycle of gemcitabine (N=44), followed by post-SBRT gemcitabine until evidence of disease progression. Two validated questionnaires, the European Organization for Research and Treatment of Cancer (EORTC) QLQ-C30 and pancreatic cancer-specific QLQ-PAN26, were administered to patients prior to SBRT and at 4-weeks and 3 to 4-months following SBRT. Results: QoL questionnaires were available for 43 patients (88%) in the clinical trial at enrollment, of whic...