Proton therapy for skull-base adenoid cystic carcinomas: A case series and review of literature

• Published in: Journal of cancer research and therapeutics Vol. 18; no. 3; pp. 629 - 637
• Main Authors: Nangia, Sapna, Gaikwad, Utpal, Noufal, M, Chilukuri, Srinivas, Patro, Kartikeswar, Nakra, Vineet, Panda, Pankaj, Mathew, Ashwathy, Sharma, Dayananda, Jalali, Rakesh
• Format: Journal Article
• Language: English
• Published: Mumbai Wolters Kluwer India Pvt. Ltd 01.07.2022; Medknow Publications and Media Pvt. Ltd; Medknow Publications & Media Pvt. Ltd
• Subjects: Care and treatment; Case studies; Dosimetry; Head & neck cancer; Head and neck cancer; Proton beam radiotherapy; Radiation therapy; Salivary gland tumors; Skull; India; proton therapy; head-and-neck cancer; Adenoid cystic carcinoma; radiation therapy
• ISSN: 0973-1482; 1998-4138
• DOI: 10.4103/jcrt.jcrt_1236_21

Purpose: An indolent nature, with a high risk of local recurrence along with the potential for distant metastases, makes the relatively rare adenoid cystic carcinomas (ACCs) of the head-and-neck region, a unique entity. In the base of skull (BOS) region, these cancers require radiation doses as high as 70-72 GyE in proximity to critical structures. Proton therapy (PT) confers physical and radiobiological advantages and local control at 2-5 years exceeding 80% in most series, compared with below 60% with photon-based techniques. We report a case series of ACCs of the BOS, treated with image-guided, intensity-modulated PT (IMPT). Materials and Methods: During 2019-2020, we treated six patients with skull-base ACC IMPT with on-board, cross-sectional image guidance. Dosimetric data, toxicity, and early outcomes were studied, and a comparative review of literature was done. Results: Three patients underwent PT/proton-photon treatment for residual/inoperable lesions and three patients underwent reirradiation for recurrent lesions. The prescription was 70 GyE in 31-35 fractions, and 95% of the clinical target volume (CTV) received 98% of the prescribed dose in five of the six patients. Grade 3 mucositis and skin reactions were noted in two patients and one patient, respectively. Five of the six patients were controlled locally at a median follow-up of 15 months. Conclusion: The radiobiological and physical characteristics of PT help to deliver high doses with excellent CTV coverage in skull-base ACCs, adjacent to critical neurological structures.