Hematologic Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_41_2461 - Involved site vs extended field radiation therapy for multiple myeloma of long bones after internal fixation

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

Involved site vs extended field radiation therapy for multiple myeloma of long bones after internal fixation
A. Elhammali1, B. Dabaja1, J. R. Gunther1, A. K. Yoder2, B. Moon3, D. Weber4, S. Thomas4, T. Andraos1, N. Garg4, B. Amini5, E. E. Manasanch4, K. Patel4, R. Orlowski4, H. Lee4, J. Bird3, R. Satcher3, P. Lin3, C. C. Pinnix1, and S. A. Milgrom1; 1The University of Texas MD Anderson Cancer Center, Division of Radiation Oncology, Houston, TX, 2Baylor College of Medicine, Houston, TX, 3University of Texas MD Anderson Cancer Center, Department of Orthopedic Oncology, Division of Surgery, Houston, TX, 4The University of Texas MD Anderson Cancer Center, Houston, TX, 5Dept. of Radiology, The University of Texas MD Anderson Cancer Center, Houston, TX

Purpose/Objective(s): Myelomatous lesions may cause destruction of the long bones, necessitating surgical stabilization with internal fixation. Radiation therapy (RT) is given frequently after surgery. Historically, the entire rod was treated post-operatively. In an effort to minimize bone marrow toxicity from RT, we have transitioned to involved site RT (ISRT), irradiating only the initial site of disease. We aimed to compare the outcomes of patients treated with ISRT vs extended field RT (EFRT).

Materials/Methods: An institutional chart review was conducted of patients with multiple myeloma (MM) treated with RT to a long bone following internal fixation with an intramedullary rod or plate. EFRT was defined as irradiation of the entire rod or plate. ISRT was defined as irradiation of the pre-operative extent of disease without encompassing the entire rod or plate. Recurrence was defined as radiographic evidence of bony disease progression anywhere within the initially involved bone, after the completion of RT.

Results: 33 patients and 40 sites treated between 2004 and 2017 were identified. The median age at time of RT was 65 years. The involved bone was the femur in 18 cases (45%). EFRT was used for 21 sites, and ISRT was used for 19 sites. The median BED was 29.8 Gy and 25.0 Gy for EFRT and ISRT, respectively (p=.12, assuming α/β of 10). The median fraction number was 10 for EFRT and 8 for ISRT, range 5-15 (p=.25). The most common fractionation schemes were 20 Gy in 10 fractions (20.5%), 25 Gy in 10 fractions (18.9%), and 20 Gy in 8 fractions (15.4%). The median follow-up time was 8.7 and 15.8 months for EFRT and ISRT, respectively (p = .30). One patient in each group underwent repeat surgery for hardware failure (p = .99 EFRT vs ISRT). Both events were purely mechanical and were not associated with recurrent disease. There were 4 instances of recurrence within the initially involved bone: one recurrence was within the RT field, and 3 were out-of-field. The in-field recurrence was observed in a patient who had been treated with ISRT and was managed with re-irradiation. Out-of-field recurrences were observed after EFRT in 2 cases and after ISRT in 1 case (p =.99 EFRT vs ISRT). For the EFRT cases, out-of-field recurrences were proximal or distal to the rod and to the RT field. For the ISRT case, the sole out-of-field recurrence was along the rod and was treated with RT to address the new disease site.

Conclusion: For MM involving long bones after internal fixation, involved site radiation fields achieve comparable disease control when compared to extended radiation fields encompassing the entire rod. The risk of disease progression along the rod, outside of the RT field, is low after RT targeting only the site of the destructive lesion.

Author Disclosure: A. Elhammali: None. B. Dabaja: None. A.K. Yoder: None. B. Moon: None. D. Weber: None. E.E. Manasanch: None. R. Orlowski: None. H. Lee: None.

Adnan Elhammali, MD, PhD

Disclosure:
No relationships to disclose.

Presentation(s):

Send Email for Adnan Elhammali


Assets

MO_41_2461 - Involved site vs extended field radiation therapy for multiple myeloma of long bones after internal fixation



Attendees who have favorited this

Please enter your access key

The asset you are trying to access is locked. Please enter your access key to unlock.

Send Email for Involved site vs extended field radiation therapy for multiple myeloma of long bones after internal fixation