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OBJECTIVE: To investigate whether photon or proton-based stereotactic body radiation therapy (SBRT is the preferred modality for high dose hypofractionation prostate cancer treatment. Achievable dose distributions were compared when uncertainties in target positioning and range uncertainties were appropriately accounted for. METHODS: 10 patients with prostate cancer previously treated at our institution (Montefiore Medical Center) with photon SBRT using volumetric modulated arc therapy (VMAT) were identified. MRI images fused to the treatment planning CT allowed for accurate target and organ at risk (OAR) delineation. The clinical target volume was defined as the prostate gland plus the proximal seminal vesicles. Critical OARs include the bladder wall, bowel, femoral heads, neurovascular bundle, penile bulb, rectal wall, urethra and urogenital diaphragm. Photon plan robustness was evaluated by simulating 2 mm isotropic setup variations. Comparative proton SBRT plans employing intensity modulated proton therapy (IMPT) were generated using robust optimization. Plan robustness was evaluated by simulating 2 mm setup variations and 3% or 1% Hounsfield unit (HU) calibration uncertainties. RESULTS: Comparable maximum OAR doses are achievable between photon and proton SBRT, however, robust optimization results in higher maximum doses for proton SBRT. Rectal maximum doses are significantly higher for Robust proton SBRT with 1% HU uncertainty compared to photon SBRT (p = 0.03), whereas maximum doses were comparable for bladder wall (p = 0.43), urethra (p = 0.82) and urogenital diaphragm (p = 0.50). Mean doses to bladder and rectal wall are lower for proton SBRT, but higher for neurovascular bundle, urethra and urogenital diaphragm due to increased lateral scatter. Similar target conformality is achieved, albeit with slightly larger treated volume ratios for proton SBRT, >1.4 compared to 1.2 for photon SBRT. CONCLUSION: Similar treatment plans can be generated with IMPT compared to VMAT in terms of target coverage, target conformality, and OAR sparing when range and HU uncertainties are neglected. However, when accounting for these uncertainties during robust optimization, VMAT outperforms IMPT in terms of achievable target conformity and OAR sparing. ADVANCES IN KNOWLEDGE: Comparison between achievable dose distributions using modern, robust optimization of IMPT for high dose per fraction SBRT regimens for the prostate has not been previously investigated.

Metastases of the spinal column are common amongst cancer patients with approximately 18,000 new cases in North America each year that require urgent treatment. Historically radiation therapy doses have been limited due to the proximity of the spinal cord. However as image guidance and localization techniques have improved it has become possible to deliver higher radiation doses to the tumour whilst sparing the spinal cord. This paper presents some of the techniques undertaken at our center.

Purpose: To introduce a non-standard method of patient setup, using BellyBoard immobilization, to better utilize the localization and tracking potential of an RF-beacon system with EBRT for prostate cancer. Methods: An RF-beacon phantom was imaged using a wide bore CT scanner, both in a standard level position and with a known rotation (4° pitch and 7.5° yaw). A commercial treatment planning system (TPS) was used to determine positional coordinates of each beacon, and the centroid of the three beacons for both setups. For each setup at the Linac, kV AP and Rt Lateral images were obtained. A full characterization of the RF-beacon system in clinical mode was completed for various beacons’ array-to-centroid distances, which includes vertical, lateral, and longitudinal offset data, as well as pitch and yaw offset measurements for the tilted phantom. For the single patient who has been setup using the proposed BellyBoard method, a supine simulation was first obtained. When abdominal protrusion was found to be exceeding the limits of the RF-Beacon system through distance-based analysis in the TPS, the patient is re-simulated prone with the BellyBoard. Array to centroid distance is measured again in the TPS, and if found to be within the localization or tracking region it is applied. Results: Characterization of limitations for the RF-beacon system in clinical mode showed acceptable consistency of offset determination for phantom setup accuracy. The nonstandard patient setup method reduced the beacons’ centroid-to-array distance by 8.32cm, from 25.13cm to 16.81cm; completely out of tracking range (greater than 20cm) to within setup tracking range (less than 20cm). Conclusion: Using the RF-beacon system in combination with this novel patient setup can allow patients who would otherwise not be candidates for beacon enhanced EBRT to now be able to benefit from the reduced PTV margins of this treatment method.

Purpose: Photon energies 10 MV or higher are generally considered optimal for treatment of deep‐seated pelvic targets. We performed dosimetric quality assessment of Prostate IMRT plans in patients treated with 6‐MV and 16‐MV Photons, to discern if 16‐MV plan quality was superior to 6‐MV treatment plans. Methods: From our institutional database, treatment plans of 84 patients previously treated for early stage prostate cancers were included in this retrospective study. Forty‐two patients were treated with 6‐MV and forty‐two with 16‐MV. Beam energy choice was based on linac capability, physician preference and not on patient separation. All patients were planned with a coplanar 7‐F IMRT technique. The prescription dose (75.6‐Gy), optimization technique and planning objectives were similar in all patients. Dose distributions were evaluated using various indices‐Conformity‐Index (CI), Healthy‐Tissue Conformity Index (HTCI), Homogeneity‐Index (HI), Gradient‐Index (GI), Conformity‐Number (CN), Normal‐Tissue Integral Dose (NTID), Body‐mass‐index (BMI) and quality of coverage (QC). Rectal and Bladder dose‐volume indices were evaluated per RTOG guidelines. Non‐parametric Mann‐Whitney test was applied in the statistical analysis and for a p‐value

TPS6644 Background: Cancer health disparities affecting low-income and minority patients are well documented. Causes of poor outcomes include treatment delays coupled with social and financial barriers. Navigation interventions have been more commonly applied in cancer screening and in early diagnosis programs than in improving adherence to treatment among those with barriers to care. This report examines the early impact of patient navigation on adherence to prescribed cancer treatment. Methods: We put into place a Patient Navigation Program as a pilot project (supported by an Avon Foundation grant) at our public safety net hospital. Health care coverage: 58% Medicaid, 23% uninsured or undocumented. Navigator duties included care coordination, appointment reminders, patient education materials, translation services, and transportation arrangement. During a 4 month period new medical oncology practice patients felt to be at high risk received navigated care. Data collected prospectively included patient characteristics, cancer type, time from referral to first RT, and compliance with visits; this was compared with usual care historical controls immediately prior to the 4 month period. Results: Patient Navigation Program patient characteristics: N = 52 patients (22 breast cancer, 6 prostate cancer, 5 lung cancer and 19 patients with other cancers). Mean age = 55; 48% Black, 38% Hispanic, 8% Asian, 6% White. Adherence to visits, and time to first RT results are seen in the Table. Conclusions: In the first 4 months of its initiation, this Patient Navigation Program has been associated with observed improvements in adherence to chemotherapy and follow up physician visits, but no impact on time to 1st RT to date. These results document that a Patient Navigation Program can help overcome barriers to good cancer care while identifying RT as an area for further improvement. [Table: see text]

benefit was more pronounced in healthy men who had no or mild comorbidity. Our study suggests that severity of comorbidity may be a more significant predictor of improved failure-free survival than age when considering the addition of ADT to dose-escalated EBRT in patients with intermediate-risk prostate cancer. Further studies are needed to confirm our findings. Author Disclosure: S. Bian: None. D.A. Kuban: None. L.B. Levy: None. J. Oh: None. S. Choi: None. S.E. McGuire: None. T.J. Pugh: None. P.L. Nguyen: None. A.K. Lee: None. K.E. Hoffman: None.