ln this exclusive webinar, leading experts from both sides of the Atlantic came together to explore the expanding role of particle therapy in the management of primary and recurrent non-melanoma skin cancers (NMSC) :
Dr. Curtis Bryant, Associate Professor of Radiation Oncology at the University of Florida Health Proton Therapy Institute (UFHPTI), Florida, USA.
Dr. Stefan Dinu, Head of the Proton Therapy Department and Dorothée Lebhertz Ph.D, Medical Physicist, at the François Baclesse Cancer Center and CYCLHAD, Caen, France.
The main clinical outcomes, dosimetric insights, and practical considerations are summarized in the sections below.
The full webinar is offering a deeper dive into treatment strategies, planning approaches, and future directions is available by clicking on the video.
Proton therapy is emerging as a compelling modality for the management of locally advanced NMSC of the head and neck with clinical perineural invasion (PNI), a rare but aggressive presentation accounting for approximately 1-2% of cases in USA. These tumors frequently involve the trigeminal of facial nerves and may extend proximally to the skull base, trigeminal ganglion, or brainstem, often rendering surgical resection inadequate or impossible, and necessitating radiation therapy.
Clinical studies and illustrative cases suggest that proton therapy, and particularly pencil beam scanning (PBS), offers dosimetric advantages over photon techniques, enabling high-dose delivery while substantially reducing dose of critical organs at risk, including the brainstem and optic apparatus. Prospective outcome data in patients with predominantly recurrent or extensive disease, including proximal perineural spread, have shown encouraging rates of local control and disease-specific survival, with acceptable toxicity despite large treatment volumes and frequent use of concurrent chemotherapy.
Collectively, these data support proton therapy as a strategy to improve the therapeutic ratio in this challenging population, particularly for patients with skull base or intracranial perineural spread.
NMSC of the head and neck are among the most common malignancies worldwide, but a subset of high-risk tumors characterized by large size, recurrence, unfavorable anatomical location, aggressive histology, or PNI, are associated with significantly, highlighting the need for effective local treatment strategies that can safely deliver curative doses in anatomically complex regions.
Clinical studies evaluating weekly hyperfractionated proton therapy suggest that this approach may provide excellent disease control in patients with high-risk head and neck NMSC, both in the adjuvant and definitive settings. In a prospective feasibility cohort including patients with multiple high-riskfeatures and frequent perineural involvement, proton therapy achieved high rates of local control at one year, with favorable disease control and low rates of distant metastasis. Importantly, these outcomes compare favorably with historical photon-based series, particularly in the definitive setting, wherere ported local control rates are typically lower. Toxicity remained acceptable, with predominantly mild-to-moderate acute dermatitis and rare severe late effects, even in elderly or frail patients treated with hypofractionated weekly schedules.
Dosimetric and physical considerations further support the use of proton therapy for superficial head and neck NMSC. Unlike photon techniques, which often rely on bolus placement and are sensitive to air gaps that may lead to skin underdosing, PBS proton therapy can deliver high surface doses without bolus, reducing uncertainties related to setup and anatomy. Experimental dosimetric studies using dedicated surface detectors demonstrated that air gaps can result in clinically relevant dose reductions at the skin surface with photons, particularly for small fields, whereas this effect diminishes rapidly with depth. Ongoing development of proton-specific detectors aims to further characterize dose deposition in the first millimeters of skin and to better quantify the potential physical advantages of proton therapy in this setting.
In conclusion, emerging clinical and dosimetric evidence supports proton therapy, particularly weekly hyperfractionated regimens, as a promising local treatment option for selected patients with high-risk head and neck nonmelanoma skin cancers. By enabling effective dose delivery to superficial and complex targets while sparing surrounding healthy tissues and minimizing technical uncertainties, proton therapy may improve both tumor control and tolerability.
Free exclusive webinar organized by François Baclesse Cancer Center, CYCLHAD and UFHPTI. Acknowledgment is given to PTCOG, PTCOG NA, and NAPT for their support.
The statements of the healthcare professionals included in these videos reflect only their opinion and personal experience. They do not necessarily reflect the opinion of any institution with whom they are affiliated or CYCLHAD.
NMSC : Nonmelanoma skin cancers, UFHPTI : University of Florida Health Proton Therapy Institute, PNI : Perineural invasion, PBS : Pencil Beam Scanning, PTCOG : Particle Therapy Cooperative Group, PTCOG NA : PTCOG North America, NAPT : National Association for Proton Therapy.
