Stereotactic Body Radiation Therapy for Management of Locally Advanced Periorbital Tumors: Efficacy and Toxicity Profile.

BACKGROUND: The management of locally advanced periorbital skin tumors with orbital invasion is challenging. Orbital exenteration historically provides reliable local control but causes major functional and cosmetic morbidity. We evaluated stereotactic body radiation therapy (SBRT) as an eye-sparing alternative, focusing on local control, vision preservation, and toxicity.

METHODS: This retrospective series includes 26 consecutive patients with locally advanced periorbital tumors treated prospectively with SBRT. Tumors involved the canthi (zones III-IV) in 20 patients, with multi-zone involvement in 18 and complete periorbital skin invasion (zone V) in 4. Eighteen tumors violated the orbital septum; anterior orbital invasion was observed in 16, and middle orbital invasion in 14. Extraconal violation occurred in 16 patients, and intraconal invasion in 15 patients. All patients were presented with intact ipsilateral vision at baseline. SBRT was delivered using VMAT/IMRT with a simultaneous integrated boost of 35-40 Gy to GTV and 25 Gy to CTV + 2 mm over five biweekly fractions. Optic apparatus constraints included Orbit PRV and Optic N PRV maximum point ≤ 30 Gy and mean ≤ 20 Gy; Lacrimal gland mean < 26 Gy when feasible. OAR constraints were based on institutional treatment directives supported by AAPM TG-101, QUANTEC, and Emami et al. 50% received systemic therapy, including immunotherapy, targeted therapy, or chemotherapy, with some receiving combined approaches. Local and regional control and toxicities (CTCAE v5.0) were recorded; statistical analysis was primarily descriptive. Kaplan-Meier methodology was used to estimate local control and overall survival. Given the limited cohort size and heterogeneous tumor histologies, no formal comparative statistical testing was performed.

RESULTS: Twenty-four patients presented with primary cutaneous tumors and 2 had non-cutaneous histologies (solitary fibrous tumor and metastatic breast carcinoma). SBRT was delivered as definitive therapy in 19 patients and as adjuvant therapy in 7. Median planning target volumes (PTVs) were 45 cc (PTV25) and 9 cc (PTV35-40 Gy), with corresponding median D90 values of 29 and 34/42 Gy, respectively. At a median follow-up of 18 months (range 4-50 months), all patients retained intact vision. Twenty-one patients achieved complete response, one had stable disease, and three experienced locoregional recurrences-one cavernous sinus failure and two local-regional relapses. Acute toxicities were predominantly mild, including Grade 1 dermatitis (n = 15), conjunctivitis (n = 8), diplopia (n = 7), orbital pain (n = 1), and hyperpigmentation (n = 2). Grade 2 dermatitis occurred in 6 patients, while Grade 3 dermatitis was rare (n = 2), both requiring reconstructive grafting. On follow-up, late effects included blurred vision (n = 6), epiphora (n = 3), orbital pain (n = 2), and cataract progression (n = 2), with isolated cases of trichiasis (n = 1) and post-surgical ptosis (n = 2). One of four patients with zone V involvement developed a chronic corneal ulcer requiring surgical management.

CONCLUSION: SBRT with a simultaneous integrated boost is a feasible eye-sparing option for selected patients with locally advanced periorbital tumors, providing high rates of local control and vision preservation with acceptable toxicity. Prospective evaluation and longer follow-up are warranted.