Palliative Care

PV QA 3 - Poster Viewing Q&A 3

TU_29_3030 - Effect of Radiation Field Size and Dose on Local Control or Re-fracture Events After Post-Operative Radiation Following Intramedullary Nailing Procedures for Palliation of Bone Metastases

Tuesday, October 23
1:00 PM - 2:30 PM
Location: Innovation Hub, Exhibit Hall 3

Effect of Radiation Field Size and Dose on Local Control or Re-fracture Events After Post-Operative Radiation Following Intramedullary Nailing Procedures for Palliation of Bone Metastases
S. Garg1, K. Sobol2, M. Munn2, G. Shukla1, T. Stumm2, J. A. Abraham3,4, and W. Shi5; 1Sidney Kimmel Medical College at Thomas Jefferson University, Sidney Kimmel Cancer Center, Philadelphia, PA, 2Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA, 3Department of Orthopedic Surgery, Thomas Jefferson University, Philadelphia, PA, 4The Rothman Institute at Thomas Jefferson University, Philadelphia, PA, 5Dept of Radiation Oncology, Thomas Jefferson University Sidney Kimmel Cancer Center, Philadelphia, PA

Purpose/Objective(s): Pathologic fracture of long bones carries a heavy symptomatic burden in patients with metastatic malignancy. Standard therapy typically includes intramedullary nail placement to stabilize the bone, followed by palliative post-operative radiation therapy (PORT) to reduce the risk of re-fracture or local recurrence. The radiation dose and fields for this treatment approach have wide variation without uniform standards. We sought to estimate the distribution of PORT dose/fractionation, and field size, and estimate any potential association with the risk of re-fracture and/or local recurrence.

Materials/Methods: We retrospectively analyzed patients treated at our institution with pathologic fractures of long bones, treated with intramedullary nailing of the femur, tibia, or humerus, followed by post-operative palliative radiation to that site. We stratified patients by radiation fractionation (single vs multi-fraction regimen) and by radiation field size (coverage of whole hardware [full-field] vs partial coverage of hardware [limited field]), to determine if these factors may be associated with the primary endpoint, which was defined as local re-fracture and/or local recurrence of disease within the long bone. Fisher’s exact test was used for statistical comparison due to the relative paucity of events.

Results: Eighty-six evaluable patients, treated between 2010-2017, were identified. Median patient age was 60 years. Median Karnofsky performance status was 70. Median follow up was 2.6 months (range, 2 weeks to 74 months). Radiation doses ranged from 8 – 30Gy, apart from one patient who received 45Gy in 3 Gy fractions. Thirty-six patients (42%) received 8 Gy in a single fraction, and fifty (58%) received multi-fraction treatment. Ten patients (12%) underwent limited field radiation, while 47 (55%) underwent full field radiation, and 29 (34%) were unevaluable for field size. Nine patients (10%) reached the primary endpoint of local recurrence and/or local refracture, consistent with historical comparison. On Fisher’s two-sided exact test, field size was not found to correlate with local recurrence/re-fracture (p=0.366). Local recurrence/re-fracture was also not significantly associated with multi-fraction radiation, compared to those who received 8 Gy in a single fraction, although was numerically worse in the multifraction group (p=0.073).

Conclusion: Increased total dose beyond 8 Gy was not associated with improvement in local control. Similarly, irradiation of the entire hardware was not associated with improved rates of local control as compared to limited field radiation. Our findings suggest that single-fraction, limited-field palliative PORT may be sufficient to achieve adequate rates of local control, thereby allowing for expedient initiation of systemic therapy and minimal RT toxicity. Further evaluation is needed.

Author Disclosure: S. Garg: None. K. Sobol: None. G. Shukla: None. J.A. Abraham: Research Grant; Janssen, Novartis. Consultant; Zimmer Biomet.

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