Abstract
The aim of this study was to evaluate the outcome of patients with head and neck adenoid cystic carcinoma (ACC) treated using pencil beam scanning proton therapy (PBS PT) at our institution. Thirty-five patients who underwent treatment with PBS PT for ACC between 2001 and 2017 were included. Local control (LC), distant control (DC), progression-free survival (PFS), overall survival (OS) and their prognostic factors were evaluated. Adverse effects were prospectively assessed. The median patient follow-up was 30months. Prior to PT, 26 patients (74.3%) underwent surgery with R0/R1/R2 outcome in 5, 13 and 8 cases, respectively. Nine patients (25.7%) presented with inoperable disease. The 2-year LC, DC, PFS and OS was 92.2%, 77.8%, 74.3% and 88.8%, respectively. LC was influenced by patient age (p=0.002) with a significant difference between local and distant failure (median 61.3 vs. 42.3years, p=0.005). Tumor T stage was a significant risk factor for PFS (p=0.045) and tumor prognostic group affected OS (p=0.049). No significant survival advantage for operable vs. inoperable disease could be identified. The acute and late grade 3 toxicity rates were 14.3% and 6.1%, respectively. No acute or late grade 4/5 toxicities were observed. PBS PT is an effective and safe treatment for patients with head & neck ACC in both definitive and adjuvant setting. Distant metastases are the main pattern of failure. Age, tumor stage and clinical stage had a significant negative impact on LC, OS and PFS.
Highlights
Adenoid cystic carcinoma (ACC) is a rare tumor of the minor and major salivary glands
Effective radiation treatment of ACC is often challenging due to proximity to vital organs at risks (OARs) which can tolerate radiation doses significantly lower than the prescription doses required to achieve satisfactory local control [4]
In the present study we report the outcome of patients treated with pencil beam scanning proton therapy (PBS Proton therapy (PT)) for ACCs
Summary
Adenoid cystic carcinoma (ACC) is a rare tumor of the minor and major salivary glands. It typically features extensive local infiltration into the adjacent tissues and, regionally, along the neural fibers rather than into the local lymph nodes [1]. Proton therapy (PT), in particular utilizing the advanced pencilbeam scanning (PBS) delivery technique has certain physical properties which increase the chance to fulfill this goal. It uses thou sands of millimeter-thin single beams which deposit their peak energy at a precisely set depth in tissue. In the present study we report the outcome of patients treated with PBS PT for ACCs
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