Head and Neck Cancer

PV QA 2 - Poster Viewing Q&A 2

MO_32_2752 - Temporal Lobe Radiation Necrosis After Primary Radiation involving the Skull Base with Proton Therapy

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

Temporal Lobe Radiation Necrosis After Primary Radiation involving the Skull Base with Proton Therapy
K. L. Pitter1, A. Lee2, B. Neal3, C. H. J. Chow4, K. Sine3, O. Cahlon1, S. M. McBride5, J. E. Leeman1, N. Riaz5, T. Waldenberg1, M. Cohen6, I. Ganly6, J. O. Boyle6, R. J. Wong6, E. Sherman7, L. Michel8, N. Lee5, and C. J. Tsai5; 1Department of Radiation Oncology, Memorial Sloan Kettering Cancer Center, New York, NY, 2Department of Radiation Oncology, SUNY Downstate Medical Center, Brooklyn, NY, 3ProCure Proton Therapy Center, Somerset, NJ, 4Queen Elizabeth Hospital, Hong Kong, Hong Kong, 5Memorial Sloan Kettering Cancer Center, Department of Radiation Oncology, New York, NY, 6Department of Surgery, Memorial Sloan Kettering Cancer Center, New York, NY, 7Memorial Sloan Kettering Cancer Center, Department of Medical Oncology, New York, NY, 8Department of Medical Oncology, Memorial Sloan Kettering Cancer Center, New York, NY

Purpose/Objective(s): To examine the clinical and dosimetric factors associated with the development of temporal lobe necrosis (TLN) among previously non-irradiated patients who received proton radiotherapy involving the skull base.

Materials/Methods: We retrospectively identified patients without a history of prior radiation treatment who then received proton radiotherapy to tumors involving the skull base and had both clinical and radiographic follow up. Analyzed factors included age, histology, stage, history of hypertension and/or diabetes, smoking status, and composite mean dose to 2cc and composite max pixel dose for the temporal lobes. Outcomes of interest included the incidence of TLN, the grade of TLN, as well as time to development of TLN from treatment.

Results: Between 09/2013 and 03/2017, we identified 134 patients who received proton radiation to the skull base and temporal lobes with a median follow up time of 17 months (range 1-50) and median age of 59 years (14-89). The most common primary tumor was salivary gland (51.1%), followed by sinonasal (24.8%), cutaneous (10.2%) and nasopharynx (4.8%). The majority of patients (84.0%) had non-recurrent tumors with >T3 primaries (50.4%), and the most common histologies were squamous cell carcinoma (26.8%), adenocystic carcinoma (25.5%), and other salivary histologies (25.5%). The median prescribed dose was 66 CGE (range 14.8-77.0) with a total mean dose to 2cc and max pixel dose to the temporal lobes of 37.5 CGE (IQR 15.0-56.2) and 53.65 CGE (IQR 27.5 – 64.7), respectively. Four patients (2.9%) developed TLN at a median time of 6 months (1-26). The median total mean dose to 2cc and max pixel dose to the temporal lobes for TLN patients was 71.3 CGE vs 54.5 CGE (p = 0.013) and 75.4 CGE vs. 62.77 CGE (ns). Three of the 4 patients with TLN had CTCAE grade 1 event with only radiographic evidence. One had a grade 3 evens requiring resection for symptomatic management and has symptoms have improved since surgery.

Conclusion: We found that proton therapy for head and neck cancers with skull base exposure resulted low rates of symptomatic temporal lobe necrosis. Consistent with previous publications, our data shows an increase in the rate of TLN with temporal lobe doses > 70 Gy. Further detailed dosimetric data with longer follow up data is underway to better ascertain the significance of these findings. Prospective evaluation is needed to further characterize TLN for patients treated with proton therapy to the skull base.

Author Disclosure: K.L. Pitter: None. A. Lee: None. B. Neal: None. O. Cahlon: None. S.M. McBride: None. T. Waldenberg: None. M. Cohen: None. J.O. Boyle: None. N. Lee: Consultant; Lily. Advisory Board; Pfizer, Vertex, Merck.

Kenneth Pitter, MD, PhD

Disclosure:
No relationships to disclose.

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