IMRT Delivery of Preoperative High Dose Radiation Therapy With Simultaneous Integrated Boost (SIB) In Retroperitoneal Sarcomas: A Feasibility Study

Volume 93  Number 3S  Supplement 2015 disease and the use of RT, as well as the presence of regional or metastatic disease and the use of ST. The similar outcomes achieved with the addition of RT in the setting of more locally advanced disease, suggests a benefit to RT in this setting. Conclusion: MCC remains an aggressive malignancy, with poor outcomes. Surgery remains the mainstay of treatment, but the addition of RT improves outcomes compared to surgery alone, especially in the setting of locally advanced tumors. Author Disclosure: Z. Nicholas: None. W. Dooley: None. T.S. Herman: None. O. Algan: None.

3581 Intraoperative Electron Radiation Therapy (IOERT) and External Beam Radiation Therapy (EBRT) in R1-Resected Soft-Tissue Sarcomas of the Extremities: Long-term Results F. Roeder,1,2 B. Lehner,3 I. Alldinger,4 L. Saleh-Ebrahimi,2 G. Egerer,5 P.E. Huber,1 G. Mechtersheimer,6 J. Debus,7 and M. Uhl8; 1University of Heidelberg, German Cancer Research Center (DKFZ), Heidelberg, Germany, 2University of Munich (LMU), Munich, Germany, 3University of Heidelberg, Dept. of Orthopedics, Heidelberg, Germany, 4University of Heidelberg, Dept. of Surgery, Heidelberg, Germany, 5University of Heidelberg, Department of Hematology, Oncology and Rheumatology, Heidelberg, Germany, 6University of Heidelberg, Institute of Pathology, Heidelberg, Germany, 7University Hospital of Heidelberg, Heidelberg, Germany, 8University of Heidelberg, Heidelberg, Germany Purpose/Objective(s): To report our long-term results with IOERT and EBRT in R1-resected soft tissue sarcomas of the extremities. Materials/Methods: We performed a retrospective analysis of 58 patients suffering from soft-tissue sarcoma of the extremities, who received IOERT and EBRT at our institution and showed microscopic positive margins at final pathology report. Median age was 60 years and median tumor size was 8 cm. 66% of the patients presented in primary situation with 69% of the tumors located in the lower limb. Stage at presentation (UICC 7th) was as follows: Ia:2%, Ib:7%, IIa:24%, IIb:17%, III: 41%, IV:9%. The majority of patients showed high grade lesions (FNCLCC G1:9%, G2:28%, G3:64%), predominantly liposarcomas (34%) and MFH (29%). IOERT was applied to the tumor bed with a median dose of 15 Gy, using electron energies of 6-8 MeV and a median cone size of 9 cm. IOERT was preceded (12%) or followed (88%) by EBRT with a median dose of 46 Gy in all patients. 26% of the patients also received pre- and/or postoperative chemotherapy. Results: The median follow-up was 71 months (7-214) for the entire cohort and 90 months (23-214) in survivors. 11 patients (19%) showed local failures, resulting in estimated 5-year and 10-year local control rates of 75%, respectively. Local control was significantly associated with primary vs recurrent situation. 19 patients (33%) showed distant failures (mainly to the lung), transferring into estimated 5-year and 10-year distant control rates of 64%. UICC stage was significantly associated with distant control. Overall treatment failure was observed in 27 patients (47%), of whom 9 failed locally only, 16 distant only and 2 combined, resulting in 5- and 10-year estimated FFTF rates of 49%, respectively. Grading was significantly associated with FFTF. 5-and 10-year estimated overall survival rates were 71% and 57%. UICC stage was the only factor significantly associated with overall survival, although a trend was observed also for grading. Severe postoperative complications were observed in 14% of the patients, mainly as wound complications. Severe late toxicity was found in 19% of the patients. Preserved limb function without impairment in activities of daily living was achieved in 81% of the patients. Conclusion: Combination of IOERT and EBRT achieves high local control and good overall survival with acceptable toxicity and encouraging rates of preserved limb function even after R1-resections in patients with soft tissue sarcomas of the extremities. Author Disclosure: F. Roeder: None. B. Lehner: None. I. Alldinger: None. L. Saleh-Ebrahimi: None. G. Egerer: None. P.E. Huber: None. G. Mechtersheimer: None. J. Debus: None. M. Uhl: None.

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3582 Radiation Therapy Influences Outcomes in Merkel Cell Carcinoma T. Strom,1 M. Carr,1 J.S. Zager,1 F. Smith,1 C.W. Cruse,1 J.L. Messina,1 T.A. Padhya,1 N.G. Rao,2 V.K. Sondak,1 L.B. Harrison,1 A. Trotti,1 and J.J. Caudell1; 1H. Lee Moffitt Cancer Center and Research Institute, Tampa, FL, 2H. Lee Moffitt Cancer Center and Research Institute, Department of Radiation Oncology, Tampa, FL Purpose/Objective(s): Following wide excision of Merkel Cell Carcinoma (MCC), adjuvant radiation therapy (RT) is typically recommended although its influence on overall survival (OS) is uncertain. There also remains controversy as to whether RT can be avoided in selected cases, such as those with negative margins and/or node-negative disease. Materials/Methods: We reviewed 300 patients treated for non-metastatic MCC from 1989 through 2012 at a single institution. Most patients were treated with wide local excision with or without adjuvant radiation therapy. Median follow-up was 27 months. The median age was 75 years (range 1396), median pathologic tumor size 1.5 cm (range 0.2-12.5) and the majority of patients were male (70%), with node-negative (70%), head and neck primary (48%), and margin negative (88%) MCC. Patients treated with adjuvant RT were significantly younger (median age 73 vs. 77 years, respectively), more often had involved nodal disease (35% vs. 20%, respectively), and more often were treated with chemotherapy (16% vs. 4%, respectively). The median radiation dose was 5,000 cGy delivered in 25 daily fractions. Clinicopathologic and treatment variables were assessed regarding their role in local control (LC), locoregional control (LRC), disease-free survival (DFS), and OS. Results: Treatment with adjuvant RT was associated with improved LC (91% vs. 70% at 3-years, respectively; p<0.001), LRC (71.5% vs. 37.8% at 3 years, respectively; p<0.001), DFS (57.0% vs. 30.2% at 3 years, respectively; p<0.001), and OS (73% vs. 66%, respectively; pZ0.02). On multivariate analysis, adjuvant RT was independently associated with improved LC (hazard ratio [HR] 0.14, 95% confidence interval [CI] 0.060.29, p<0.001), LRC (HR 0.25, 95% CI 0.16-0.39, p<0.001), DFS (HR 0.38, 95% CI 0.27-0.54, pZ0.001), and OS (HR 0.62, 95% CI 0.41-0.94, pZ0.03). Even patients with negative margins and node-negative disease had significant improvements in LC (93% vs. 82%, respectively, pZ0.03) and LRC (75% vs. 52%, respectively, p<0.001) with adjuvant RT. Conclusion: Adjuvant RT for MCC was independently associated with improved LC, LRC, DFS, and OS. RT was beneficial regardless of margin status and nodal status. Author Disclosure: T. Strom: None. M. Carr: None. J.S. Zager: None. F. Smith: None. C.W. Cruse: None. J.L. Messina: None. T.A. Padhya: None. N.G. Rao: None. V.K. Sondak: None. L.B. Harrison: None. A. Trotti: None. J.J. Caudell: None.

3583 IMRT Delivery of Preoperative High Dose Radiation Therapy With Simultaneous Integrated Boost (SIB) In Retroperitoneal Sarcomas: A Feasibility Study S. El-Sayed1 and K. Carty2; 1University of Ottawa Ottawa, ON, Canada, 2 The Ottawa Hospital Cancer Centre, Ottawa, ON, Canada Purpose/Objective(s): Retro-peritoneal sarcomas are rare tumors which present late and are difficult to treat. The role of radiation therapy remains debatable. While no randomized controlled trials have been completed or reported, single centers prospective experiences have been favorable. More recently, a SEERS data base analysis has shown no benefit to the use of pre-operative radiation therapy. Perhaps that is not surprising as the use of radiation therapy have been hampered by the need to treat very large volumes while trying to limit the dose to sensitive organs. The dose of radiation used has been very limited in order to limit the toxicity. The purpose of that study was to assess the feasibility of large volume treatment to tolerance dose of 45 Gy while boosting the GTV to higher dose of 50-55 Gy using SIB with TOMO IMRT delivery Materials/Methods: All newly diagnosed patients with intermediate or high grade retroperitoneal sarcoma were enrolled into a prospective study

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using pre-operative radiation therapy. Patients had to have an operable tumor and no evidence of distant metastases. The majority of the tumors were fairly extensive and displacing abdominal organs. All patients were treated with megavoltage radiation with IMRT delivery. A minimum dose of 45 Gy was delivered to full volume with a margin to the PTV. An SIB was delivered to the GTV or the high dose areas to a dose of 55 GY all in 25 Daily Fractions. Surgery followed 4-6 weeks later. Results: During the period of 2011 to 2014, 23 patient s have been treated. The use of IMRT has facilitated dose delivery and escalation in a safe manner. The patterns of toxicity including bowel symptoms and delayed healing have been compared with historical controls. None of our patient has developed any significant acute toxicity necessitating stopping radiation therapy. No severe late effects have been reported. Despite the large volume treatment surgical resections have been successful in all patients. Follow-up is ranging from 6 months to 4 years. Detailed toxicity analysis will be presented at the meeting. Conclusion: Dose escalation and dose delivery to a large abdominal volume are safe and feasible in RP Sarcomas with the use of IMRT. Acute and subacute side effects are limited and much less than historical controls. It remains to be seen if that will translate into long term improvement in survival. Author Disclosure: S. El-Sayed: None. K. Carty: None.

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3584 Comparison of Treatment Planning for Carbon Ion Radiation Therapy, Proton Therapy and Intensity Modulated Radiation Therapy for Spinal Tumors Encircling the Spinal Cord K. Matsumoto,1 K. Nakamura,2 Y. Shioyama,3 T. Sasaki,1 S. Ohga,2 T. Yamaguchi,1 T. Yoshitake,4 K. Asai,1 K. Ohshima,1 M. Inamori,1 K. Hiramine,1 and H. Honda1; 1Department of Clinical Radiology, Kyushu University, Fukuoka, Japan, 2Kyushu University, Fukuoka, Japan, 3Ion Beam Therapy Center, SAGA-HIMAT Foundation, Saga, Japan, 4 Department of Comprehensive Clinical Oncology, Kyushu University, Fukuoka, Japan Purpose/Objective(s): Spinal tumors encircling the spinal cord are very difficult to excise with sufficient margins. Carbon ion radiation therapy (CIRT), proton therapy (PT) and intensity-modulated radiation therapy (IMRT) are new radiation modalities suitable for spinal tumors. The objective of this study was to compare the treatment planning for CIRT, PT with the patch-field technique and IMRT for spinal tumors surrounding the spinal cord. Materials/Methods: We conducted a treatment planning comparison among the three modalities using a phantom imitating a spinal tumor and then six actual cases with spinal tumors. The prescribed dosages and spinal cord dose constraints were determined based on previously reported treatment approaches for spinal tumors. The prescribed doses were 64 gray equivalents (GyE; physical dose in Gy x RBE)/16 fraction for CIRT, and 77.4 Gy(E)/43 fraction for PT and IMRT. The surface/center spinal cord dose constraints were set to 48/41 GyE for CIRT and 63/54 Gy(E) for PT and IMRT. Results: The phantom study demonstrated more heterogeneity of the dose distribution in PT and a higher irradiated dose to the center of the spinal cord in IMRT compared to CIRT. In the planning comparison among the six cases, CIRT achieved better homogeneity of dose distribution (PZ0.026) and coverage of target (mean dose, PZ0.047; D90% (the doses received by at least 90% of the target), PZ0.009) compared to PT. IMRT exhibited the most homogeneous dose distribution but the highest spinal cord dose, and it showed significantly deteriorated homogeneity of dose distribution and coverage of the target depending on the extent to which the tumor encircled spinal cord. Conclusion: CIRT using the patch-field technique was found to be most appropriate for the treatment of advanced spinal tumors. Author Disclosure: K. Matsumoto: None. K. Nakamura: None. Y. Shioyama: None. T. Sasaki: None. S. Ohga: None. T. Yamaguchi: None. T. Yoshitake: None. K. Asai: None. K. Ohshima: None. M. Inamori: None. K. Hiramine: None. H. Honda: None.

Stereotactic Radiosurgery for Primary and Metastatic Sarcomas of the Spine D. Boyce-Fappiano,1 E. Elibe,1 S. Ryu,2 M.S.U. Siddiqui,1 I. Lee,1 J. Rock,1 and F. Siddiqui1; 1Henry Ford Health System, Detroit, MI, 2Stony Brook University, Stony Brook, NY Purpose/Objective(s): The management of spinal or paraspinal sarcomas poses unique challenges. They have irregular borders making surgical resection difficult and require much higher doses of radiation to achieve a favorable clinical and radiographic response. Little research has been performed to determine the role of SRS in sarcomas of the spine. The goal of this institutional analysis is to evaluate the role of SRS in primary and metastatic spinal or paraspinal sarcomas. Materials/Methods: Patients with pathologically confirmed sarcomas that received spine SRS at our institution between June 2001 and December 2013 were retrospectively reviewed after obtaining IRB approval. EMRs of clinical exams, and computed tomography/magnetic resonance imaging were evaluated. Post treatment pain control, neurological improvement, and radiographic tumor control were the primary endpoints of this study. Results: A total of 23 patients treated to 78 vertebral levels were included. The average age of the cohort was 57 years. 45% of the patients were male and 55% were female. 64% were Caucasian, 27% African American, and 9% were of other ethnicities. The median surgical dose was 18 Gy in a single fraction (range 10-20) prescribed to the 90% isodose line. Median follow-up time was 3 months. 14 patients were deceased with a median survival of 14.6 months. Leiomyosarcoma was the most common histology among the cohort with 9 patients. Other histologies included- Ewing’s (3), osteosarcoma (2), neufibrosarcoma (2), liposarcoma (2), chondrosarcoma (1), hemangiopercytoma (1), rhabdomyoblastic anaplastic (1), spindle cell (1), and unspecified sarcoma(1). The average tumor volume was 53.12 cc (range 2.02-207.25cc). Overall pain response was 75% (25% partial & 50% complete relief). Pain was stable in 25% of the patients, and no pain progression was observed. Total neurological response was 25% (0% complete, 25% partial). 94% of the patients were neurologically stable or improved after treatment. In one patient (6%) a progressed neurological deficit was observed. Total radiographic response was 67% (0% complete, 29% partial, 38% stable). Local tumor progression was observed in 33% of the patients. One patient initially had a partial radiographic response that progressed after 10 months. Another patient was initially stable but experienced radiographic progression after three months. Eight vertebral compression fractures (VCFs) were noted, two of which may be attributed to SRS. No other adverse effects were observed. Conclusion: A total of 23 patients and 78 spinal levels were treated with SRS resulting in fairly good response rates for pain relief, neurologic improvement, and radiographic tumor response (75%, 25%, & 67% respectively). Our results indicate that SRS has a role in the treatment of primary and metastatic sarcomas of the spine. Using slightly higher doses may provide improved response rates. Author Disclosure: D. Boyce-Fappiano: None. E. Elibe: None. S. Ryu: Research Grant; Varian Medical Systems, Palo Alto, CA. directs clinical affairs; Stony Brook Medicine. overseas department; Stony Brook Medicine. M.U. Siddiqui: Research Grant; Varian Medical Systems, Palo Alto, CA. I. Lee: None. J. Rock: None. F. Siddiqui: Research Grant; Varian Medical Systems, Palo Alto, CA. ASTRO annual meeting scientific committee; ASTRO. ASTRO Liaison; Medical Dosimetry Certification Board. overseas department; Henry Ford Hospital.

3586 Superficial X-rays Versus Surface Brachytherapy for Non-Melanoma Skin Cancer: A Matched Pair Analysis D. Olek, S. Vyas, M.M. Gestaut, D. Arora, S.G. Jhavar, S. Hasan, N. Thawani, C. Ord, N. Deb, J. Smith, and S. Mutyala; Baylor Scott & White Healthcare Temple Clinic, Temple, TX Purpose/Objective(s): The gold standard definitive treatment for early stage nonmelanoma skin cancers (NMSC) is surgery. However, depending