2799 - Evaluation of Efficacy and Safety of Proton Reirradiation in Head and Neck Cancers: Institutional Outcomes and Toxicity Profile Analysis
Presenter(s)
T. MacDonald1, S. Dubbaka2, S. Medek1, and K. P. Redmond1; 1Department of Radiation Oncology, University of Cincinnati Cancer Center, Cincinnati, OH, 2University of Cincinnati College of Medicine, Cincinnati, OH, United States
Purpose/Objective(s): Head and neck (HN) malignancy patients face a high risk of disease recurrence and development of secondary primary cancers. While surgery is the preferred treatment option, it is often not feasible due to tumor location or prior treatments. Re-irradiation (ReRT) can be effective but poses a heightened risk of severe toxicities and substantial clinical morbidity. Proton therapy may help decrease dose to normal structures and mitigate toxicities. While proton ReRT is promising, few studies have explored long term toxicities as well as survival. Our study aims to address these concerns.
Materials/Methods: A retrospective cohort study was conducted, identifying all patients treated with proton ReRT in the HN region from 2016-2020 at our institution. Patient data was compiled including demographics, performance status, details of prior radiation, interval between treatment courses, MIRI subgroup classification, toxicities, recurrence details and survival. Toxicities were evaluated using the Common Terminology Criteria for Adverse Events (CTVAE) Version 5.0.
Results: Data was analyzed for 84 patients [median follow up 18.25mo]. The median age was 65, 65% were male, and 55% were treated for second primary cancers. The time between RT courses ranged from 177 days to over 40 years, with a median time to ReRT of 8.3 years. Patients were grouped by MIRI RPA subgroups, with OS analyzed for each class as shown in table. At the time of analysis, 67% (56pt) were deceased (median time to death: 12mo) and 63% (53pt) experienced disease progression (median 3.8mo). Local failure occurred in 50% (42pt, median 4mo), and distant failure in 27% (23pt, median 7mo). Among 71 patients with a functional larynx, 10% (7pt) required tracheostomy (median 7.5mo), and one required total laryngectomy for chondronecrosis. 27% of patients required a feeding tube post-treatment (median 14mo). Acute toxicities included G3+ in 63% (51pt), with 12% (10pt) experiencing G4 events. Late toxicities included G3+ in 72% (56pt), with 29% (23pt) experiencing G4 events and 1 G5 fatality due to carotid blowout (8mo post ReRT). Temporal lobe radiation necrosis occurred in 10% (8pt), with 4% (3pt) requiring surgery. Osteoradionecrosis (ORN) was observed in 23% (18pt), with 18% (14pt) requiring surgery.
Conclusion: We reviewed 84 cases of proton re-irradiation done at our facility to explore toxicity profiles and survival data. There was a high recurrence rate with over 63% patients having disease progression within 4 months of ReRT. 1yr OS was 33% and survival corresponded well to MIRI RPA class. Late toxicities were frequently noted with 72% having G3+ late toxicities, the most frequent being ORN (23%) and temporal lobe radionecrosis (10%). Our data highlight that while proton ReRT is an option in the setting of recurrent HN malignancy, patient selection is of utmost importance due to high potential for morbidity and limited survival benefit.
Abstract 2799 - Table 1| MIRI Class | n | Median OS (mo) |
| 1 | 33 (39%) | 26 |
| 2 | 44 (52%) | 16 |
| 3 | 7 (8%) | 3 |