Sarcoma and Cutaneous Tumors

PV QA 2 - Poster Viewing Q&A 2

MO_20_2607 - Efficacy of SBRT for Local Control in Recurrent and Metastatic Sarcoma

Monday, October 22
10:45 AM - 12:15 PM
Location: Innovation Hub, Exhibit Hall 3

Efficacy of SBRT for Local Control in Recurrent and Metastatic Sarcoma
C. Brett1, N. B. Newman2, E. Kim1, E. Jeans3, and E. T. Shinohara4; 1Vanderbilt University Medical Center, Nashville, TN, 2Department of Radiation Oncology Vanderbilt University Medical Center, Nashville, TN, 3Rush University Medical Center, Chicago, IL, 4Va, Amsterdam 1007 MB, Netherlands

Purpose/Objective(s): The development of Stereotactic Body Radiation Therapy (SBRT) has facilitated the precise and safe delivery of increased doses of radiation with limited exposure of surrounding tissues. One venue where this can be of utility is in the treatment of radio-resistant tumors. In this single institution retrospective study, we sought to examine the effectiveness of SBRT for local control in metastatic and locally recurrent sarcoma and factors correlated with local failure.

Materials/Methods: A retrospective, IRB approved review of patients treated with SBRT for locally recurrent or metastatic sarcoma was performed, with compilation of patient and treatment related factors including age, gender, histology, tumor size, location, dosimetric data, time to recurrence, and vital status at follow-up. Cox proportional hazard models were constructed to determine relationship between treatment and patient factors and time to recurrence. Time to recurrence or progression was calculated from the completion of radiation treatment.

Results: Twenty nine lesions in seventeen patients were treated from January 2011 to September 2016. Tumor histology included eight cases of Ewing’s Sarcoma (28%), six cases of Osteosarcoma (21%), 7 cases of Chondrosarcoma (24%) including two dedifferentiated tumors, as well as 8 other cases including such histologies as Synovial sarcoma, Pleomorphic sarcoma, and Leiomyosarcoma. Median follow-up time was 154 days. In this time, there were seven lesions (24%) that recurred or progressed in four patients (Local control 76%). Median time to recurrence in these patients was 159 days (28 to 686 days). Median total radiation dose was 24 Gy in lesions which recurred and 28.8 Gy in those who did not. Treatment was delivered over a median of 5 fractions in both cohorts. Univariable cox regression analysis revealed dose escalation was associated with decreased chance of recurrence (HR 0.90, p=0.047). Significance was retained on bivariable cox regression analysis accounting for bony vs. soft tissue mets/recurrences (HR 0.895 p=0.046). Associations with dose per fraction, gender, age, and bony vs. soft tissue site did not reach significance.

Conclusion: SBRT provides an effective way to escalate radiation dose to tumor with relative sparing of surrounding tissues, and can be a useful tool in the treatment of radio-resistant tumors. In this retrospective analysis we see evidence of utility of SBRT for local control of metastatic and recurrent sarcoma, with modest benefit of dose escalation. Further studies will be required to explore optimal dose and fractionation as well as histologies best suited to management by this technique.

Author Disclosure: C. Brett: None. N.B. Newman: None. E. Kim: None. E.T. Shinohara: None.

Christopher Brett, MD

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