Gastrointestinal Cancer

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SU_2_2015 - Metastasis-Directed Stereotactic Body Radiation Therapy for Oligometastatic Colorectal Cancer: a Single Institution Experience

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Metastasis-Directed Stereotactic Body Radiation Therapy for Oligometastatic Colorectal Cancer: a Single Institution Experience
K. R. Jethwa1, S. Jang1, K. Olivier1, S. S. Park1, K. W. Merrell2, J. A. Martenson1, M. A. Neben-Wittich1, K. W. Roberts1, A. L. H. Arnett1, J. M. Hubbard3, T. J. Whitaker1, W. S. Harmsen4, L. A. Waltman5, B. R. Kipp5, A. Grothey3, M. G. Haddock1, and C. L. Hallemeier1; 1Department of Radiation Oncology, Mayo Clinic, Rochester, MN, 2Mayo Clinic, Rochester, MN, 3Division of Medical Oncology, Mayo Clinic, Rochester, MN, 4Division of Biomedical Statistics and Informatics, Mayo Clinic, Rochester, MN, 5Department of Laboratory Medicine and Pathology, Rochester, MN

Purpose/Objective(s): To report our institutional experience utilizing stereotactic body radiation therapy (SBRT) for patients with oligometastatic or oligoprogressive colorectal cancer (CRC).

Materials/Methods: Following institutional review board approval, a retrospective chart review was performed to identify patients with oligometastatic or oligoprogressive CRC who received metastasis-directed SBRT. Patient characteristics, treatment characteristics, and oncologic outcomes were collected. Overall survival (OS) from end of first SBRT and local control (LC) were estimated using Kaplan-Meier methods and cumulative incidences, respectively.

Results: A total of 85 patients (31 male, 54 female) and 107 lesions were treated between 2008 and 2017. Median follow-up was 20 months (interquartile range [IQR] 10, 41). Median age was 62 (IQR 53, 70). The primary tumor site was colon (63%) or rectum (37%). Forty-one (48%) patients were diagnosed with metastatic disease at initial disease diagnosis. At metastatic diagnosis, most patients were found to have ≤ 5 metastatic lesions (93%), with most having involvement of 1 (83%) or 2 (14%) organs. Median time from development of metastasis to SBRT was 30 months (IQR 15, 52). All patients received chemotherapy prior to first SBRT. The majority (84%) of patients received other modalities of metastasis-directed local therapy prior to SBRT, including surgery (66%), ablative procedure (34%), conventional palliative dose radiotherapy (RT) (21%), or embolization (2%). Median lesion size treated with SBRT was 2.2 cm (IQR 1.4, 3.8). Table 1 demonstrates the distribution of lesions, 3-year OS, site-specific treatment information, and 3-year LC outcomes. Variables associated with local recurrence were lower biologically effective dose (assuming an α/β = 10, BEDGy10) (HR 0.89, 95% CI 0.80 – 0.99) and larger lesion size (HR 1.32, 95% CI 1.10 – 1.58), when analyzed as continuous variables at 10 Gy and 1 cm increments, respectively. Three-year LC was 81% for lesions receiving BEDGy10 ≥ 113 (the group median dose) versus 48% for BEDGy10 < 113 (p<0.01). The predominant first site of disease progression was distant metastasis outside of SBRT field (76%).

Conclusion: SBRT is an effective means of obtaining long-term local control for patients with oligometastatic CRC, with some patients experiencing long term survival. Higher SBRT doses were associated with better local control.
Table 1: OS, Treatment Characteristics, and Local control of CRC Metastasis Treated with SBRT
Site N Dose (Gy) # fractions BEDGy10 3-year LC 3-year OS
- 85 - - - - 46% (34% - 59%)
All 107 50 (48, 54) 4 (3, 5) 113 (100, 151) 72% (64% - 82%) -
Lung 42 54 (48, 54) 3 (3, 4) 151 (105, 151) 80% (68% - 93%) -
Liver 34 60 (53, 60) 5 (5, 5) 132 (127, 151) 70% (55% - 89%) -
Bone 16 30 (26, 49) 3 (3, 5) 63 (60, 96) 43% (24% - 79%) -
Lymph Node 10 50 (44, 50) 5 (5, 5) 100 (82, 100) 100% (69% - 100%) -
Other 5 45 (36, 50) 5 (5, 5) 86 (61, 100) 75% (43% - 100%) -
* Continuous variables reported as the median (IQR), survival and LC reported as percentage (95% CI)

Author Disclosure: K.R. Jethwa: None. S. Jang: None. K. Olivier: Stock; ViewRay Incorporated. S.S. Park: None. K.W. Merrell: None. J.A. Martenson: None. M.A. Neben-Wittich: None. T.J. Whitaker: None. A. Grothey: None. M.G. Haddock: Board Member; ISIORT. C.L. Hallemeier: Research Grant; Mayo Clinic.

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