2357 - To Radiate or Not: The Role of Consolidative Radiotherapy to Post-Induction MIBG-Avid Sites in High-Risk Neuroblastoma
Presenter(s)
A. C. Merritt1, S. Dash2, J. Chapman3, T. Dan2, M. Kozak2, A. Sadanand3, T. C. Watt4, and K. A. Kumar2; 1University of Texas Southwestern Medical School, Dallas, TX, 2Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, TX, 3University of Texas Southwestern Medical Center, Dallas, TX, 4Department of Pediatric Oncology, Children's Hospital, University of Texas Southwestern Medical Center, Dallas, TX
Purpose/Objective(s): In high-risk metastatic neuroblastoma, radiation treatment (RT) is recommended to the primary site after surgery, as well as to metastatic sites remaining MIBG-avid post-induction chemotherapy. However, data for the latter is limited, and our practice has generally been to withhold RT to these sites. This study examines patterns of failure in high-risk metastatic neuroblastoma patients with persistent post-induction MIBG-avid disease to better determine the value of metastatic site RT.
Materials/Methods: We performed an IRB-approved retrospective review of high-risk neuroblastoma patients treated from 2010–2020. Included patients had MIBG-avid metastatic disease at diagnosis and first relapse, achieved partial or complete response before first relapse, and did not receive total body radiation or 131I-MIBG therapy prior to relapse. Of 41 patients treated, 25 had persistent MIBG-avid disease on post-induction scan; 19 had adequate follow-up and formed the primary cohort. We compared the locations of sites at initial relapse with sites that were MIBG-avid on post-induction scans and calculated rates of relapse for sites that received RT versus those that did not.
Results: Among 19 evaluable patients, 154 active metastatic sites were identified on post-induction MIBG scan; 33 were irradiated. With a median follow-up of 56 months, 10/19 patients (53%) recurred with 23 total sites at first relapse. Of these, 9 (39%) were previously MIBG-avid sites (2 radiated, 7 not), 2 (9%) were primary tumor sites, and 12 (52%) were new sites. Local control (LC) at radiated metastatic sites was 100% (33/33); LC at non-radiated residual sites was 94% (114/121). In per-patient analysis, 4/10 recurrences (40%) involved prior MIBG-avid sites, with 3 of those 4 patients having a previously MIBG-avid site as their sole initial recurrence.
Conclusion: In this cohort, ~40% of recurrences occurred in prior residual post-induction chemo MIBG-avid sites, and 30% of patients who recurred had initial recurrences only in previously MIBG-avid sites that were not irradiated, suggesting that consolidative metastatic site RT may have been beneficial in these patients. Radiated sites achieved 100% LC, however 94% of non-irradiated sites also did not recur, indicating that the large majority of metastatic sites may not need consolidative RT and that appropriate selection and weighing benefits vs risks is important. Further studies are needed to elucidate prognostic factors to better risk-stratify which patients and sites would benefit most from consolidative metastatic site RT.