3441 - Four-Year Results of a Phase I/II Single-Arm Prospective Clinical Trial of Stereotactic Magnetic Resonance Guided Adaptive Radiation Therapy (SMART) for Metachronous Oligometastatic Abdominopelvic Lymph Node and Soft Tissue Metastases
Presenter(s)
T. Howard1, G. Benham1, S. Chirmade1, D. D. Yang2, V. S. Brennan3, D. N. Cagney4, J. E. Leeman5, Z. Han5, and M. A. Huynh6; 1Department of Radiation Oncology, Brigham and Women’s Hospital, Dana-Farber Cancer Institute and Harvard Medical School, Boston, MA, 2Department of Radiation Oncology, Brigham and Women’s Hospital/Dana-Farber Cancer Institute, Boston, MA, 3Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 4Radiotherapy Department, Mater Private Network, Dublin, MA, Ireland, 5Department of Radiation Oncology, Dana-Farber Cancer Institute/Brigham and Women’s Hospital, Harvard Medical School, Boston, MA, 6Department of Radiation Oncology, Brigham and Women's Hospital, Dana-Farber Cancer Institute, Harvard Medical School, Boston, MA
Purpose/Objective(s): Growing evidence supports local treatment of oligometastatic cancer. Metachronous oligometastases develop after definitive treatment of the primary tumor and may represent a favorable disease state amenable to a curative approach. SMART provides optimal imaging and precise targeting of nodal and soft tissue metastases in the abdomen and pelvis due to proximity to mobile luminal gastrointestinal organs-at-risk. The primary objective of this trial was to determine the feasibility and safety of SMART for the treatment of metachronous oligometastases. Secondary objectives included assessing rates of acute toxicities and evaluating local control (LC).
Materials/Methods: Patients eligible for enrollment were diagnosed with solid-tumor metachronous malignancy with abdominopelvic nodal or soft tissue metastases, =7cm in maximal diameter, and =3 sites of active disease. All patients received 40 Gy in 5 fractions. Patients were evaluated for acute toxicities at 1-2, 3-5, 6-8, and 9-12 months as graded per CTCAEv5. Patients were then followed by their radiation and medical oncology teams as clinically appropriate. LC, distant progression-free survival (dPFS), overall survival (OS), and need for additional local or systemic therapies were determined by chart review.
Results: Ten patients were enrolled and all successfully treated with SMART. Eight were treated for prostate cancer (PCa) and two for renal cell carcinoma (RCC). All were male. The median age at treatment was 67.0 years (range: 39.3 – 79.3 years). The median follow-up after SMART was 3.9 years (range: 2.1 – 4.3 years). Three patients experienced acute grade 1 toxicities; there were no higher grade or long-term toxicities. One patient with RCC progressed both locally and distantly and died of disease. All other patients remain alive with their SMART targets locally controlled (3-year LC and OS: 90%). Eight total patients recurred distantly (median dPFS: 1.6 years; 3-year dPFS: 40%) with six changing systemic therapy and five receiving additional courses of radiotherapy. Among patients with PCa, six (75%) received a break in androgen deprivation therapy (ADT) prior to recurrence. No patients were switched to chemotherapy. Two patients (one PCa, one RCC) remain with no evidence of disease (NED), each at over three years following SMART.
Conclusion: With four years median follow-up, this small prospective clinical trial reports low rates of SMART-related toxicity, excellent LC, encouraging OS, and 20% of patients with NED, supporting metastasis-directed therapy for metachronous oligometastases.