IMRT With Planned Gamma Knife Radiosurgery Boost for Head and Neck Cancer With Extensive Disease in Proximity to Critical Structures

• Published in: International journal of radiation oncology, biology, physics Vol. 111; no. 3; pp. e380 - e381
• Main Authors: Farris, J.C., Steber, C., Chan, M.D., Cramer, C.K., Ververs, J.D., Black, P.J., Frizzell, B.A., Laxton, A., Tatter, S.B., Waltonen, J., Patwa, H.S., Sullivan, C.A., Browne, J.D., Greven, K.M., Hughes, R.T.
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 01.11.2021
• ISSN: 0360-3016; 1879-355X
• DOI: 10.1016/j.ijrobp.2021.07.1116

To describe outcomes of a novel paradigm of intensity-modulated radiotherapy (IMRT) in combination with planned Gamma Knife Radiosurgery (GKRS) boost for locally advanced head and neck cancer (HNC) with extensive disease near critical organs at risk (OAR). Patients with HNC treated with IMRT/GKRS as part of a planned combined modality approach between 2011-2020 (n = 18) were reviewed. Histology, site (primary/GKRS target), extent of invasion, cumulative radiation dose, and patterns of failure were recorded. Local control (LC) [freedom from failure within the GKRS 50% IDL], marginal failure (MF) [freedom from failure between the 50% IDL and edge of IMRT volume], overall survival (OS) and disease specific survival (DSS) were estimated using Kaplan Meier method. 18 patients met inclusion criteria. Histology included 9 squamous cell carcinomas, 2 adenoid cystic carcinomas and 1 each of the following: adenocarcinoma, melanoma, neuroendocrine tumor, sinonasal undifferentiated carcinoma, nasopharyngeal carcinoma, angiosarcoma, and chondrosarcoma. Median age was 64 years. Tumor stage was primarily advanced: T2 (n = 1), T3 (1), T4 (15). Involved structures prompting GKRS utilization included: base of skull (n = 14), mucosal sinus (9), intracranial (5), cavernous sinus (8), extracranial skull base (8), orbit (5). Twelve patients had surgical resection to their primary site and 7 had surgery involving the GKRS site. Median IMRT dose to the primary site was 57.8 Gy (30.6 – 69.3) in 30 fractions (17-35) and 45 Gy (30.6-60.0) to the GKRS site. Median GKRS dose was 12 Gy (8-17) prescribed to the 50% IDL (48-50). All but one GKRS was delivered with a single fraction. With a median follow up was 27.4 months (range 1.9-111.0), GKRS site LC was 100%; 2 patients experienced primary site failure outside of the GKRS site, 1 patient experienced a MF. 2- and 5-year OS were 94.1% (95% CI: 83.6%-100%) and 80.1% (95% CI: 58.3%-100%), respectively. 2- and 5-year DSS were 92.9% (95% CI: 68.8%-80.3%) and 81.2% (95% CI: 12.4%-60.2%), respectively. 3 patients experienced radionecrosis of the brain with grade 1 (n = 2) and grade 3 (n = 1) toxicity observed, one of which was biopsy proven. No patients experienced change or worsening of vision or other baseline symptoms including headache, diplopia, or trigeminal nerve pain. Median D0.03cc (EQD2, α/β = 3) to critical OAR were: right optic nerve (47 Gy, interquartile range [IQR] 33.0 – 52.4), left optic nerve (36.8, IQR 25.6 – 53.7), optic chiasm (41.5, IQR 26.9 – 47.7), brain (95.9, IQR 77.1 – 144.0), brainstem (49.6, IQR 34.2 – 56.6), and cervical spinal cord (15, IQR 5.8 – 23.0). IMRT combined with planned GKRS conformal boost results in excellent LC with minimal additional toxicity. This paradigm represents a promising means of dose escalation for locally advanced HNC with extension to critical OAR.