Radiation associated brain image changes after proton therapy for skull base head and neck cancers

Abstract

Background and purpose: To characterize patterns and outcomes of brain MR image changes after proton therapy (PT) for skull base head and neck cancer (HNC). Material and methods: 127 patients treated with PT for HNC who had received at least 40 Gy(RBE) to the brain and had at least 1 follow up MRI > 6 months after PT were analyzed. MRIs were reviewed for radiation-associated image changes (RAIC). MRIs were rigidly registered to planning CTs, and RAIC were contoured on T1 (post contrast) and T2 weighted sequences, and dose volume parameters extracted. Probability of RAIC over time was calculated using multistate analysis. Univariate/multivariate analyses were performed using Cox Regression. Recursive partitioning analysis was used to investigate dose volume correlates of RAIC development. Results: 17.3% developed RAIC. All RAIC events were asymptomatic and occurred in the temporal lobe (14), frontal lobe (6) and cerebellum (2). The median volume of the RAIC on post contrast T1 was 0.5 cc at their maximum size. The RAIC spontaneously resolved in 27.3%, progressed in 27.3% and improved or were stable in 29.6% of patients. The three year actuarial rate of developing RAIC was 14.3%. Brain and RAIC lesion doses were generally higher for temporal lobe RAIC compared to frontal lobe RAIC. RAIC was observed in 63% of patients when V67 Gy(RBE) of the brain exceeded 0.17 cc. Conclusion: RAIC lesions after PT were asymptomatic and either resolved or regressed in the majority of the patients. The estimated dose volume correlations confirm the importance of minimizing focal high doses to brain when achievable.

Proton Therapy for Head and Neck Cancer: A 12-Year, Single-Institution Experience

“…We have previously detailed patient and treatment characteristics, disease control, and toxicity outcomes for patients treated at our center with PT for oropharyngeal cancer [3,10,12,[21][22][23], skull base tumors [24], periorbital tumors [5], nasopharyngeal cancer [4], adenoid cystic carcinomas [6,7], and paranasal sinus tumors [11] and for patients treated with PT for reirradiation [8,9,25]. Evidence from initial comparative reports in oropharyngeal cancer from our center and others, for example, have demonstrated reduced acute toxicities [26], reduced weight loss, reduced feeding tube placement [22], reduced symptom severity during the subacute recovery period [21], reduced incidence of osteonecrosis [23], and no difference in overall survival with IMPT compared with IMRT [22].…”

NTCP Modeling for High-Grade Temporal Radionecroses in a Large Cohort of Patients Receiving Pencil Beam Scanning Proton Therapy for Skull Base and Head and Neck Tumors

“…TRN is an adverse event that may occur in a substantial number of patients treated with radiotherapy which is observed in 2-17% of patients treated for ORL and skull base tumors (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)17). Data for proton therapy shows a higher overall incidence of TRN, ranging from 9.7% -17.1% (1,8,13,17) compared to photon therapy with 2.3% -15%) (2,5,11,12,14).…”

“…Radionecroses (RN) are well-documented side effects after high-dose radiation to the brain that can occur in a considerable number of patients, especially for those with radio-resistant tumors in vicinity of critical structures, such as skull-base chordoma, chondrosarcoma or cancers of the head and neck region (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16)(17). For these tumors, the temporal lobes are especially at risk given the close anatomical proximity of the target volumes.…”

“…For these tumors, the temporal lobes are especially at risk given the close anatomical proximity of the target volumes. The incidence of temporal RN (TRN) reported in more recent series including both photon and proton treatment of skull base or otorhinolaryngology (ORL) cancers ranges from 2.3 -17.1% (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)17). For proton specific data the incidence of TRN ranges from 9.7 -17.1% (1,3,6,7,17).…”

“…Radiation necrosis of a higher grade needing at least corticosteroid treatment appear in up to 6% of patients (3,6,9). RN usually appear after a median of 17 -34 months but may occur for at least up to 5 years after radiotherapy (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14)(15)(16).…”