# Intensity-modulated radiotherapy with carbon ion boost for high-risk sinonasal squamous cell carcinoma: clinical outcomes and the management of the node-negative neck

## TL;DR

Combining intensity-modulated radiotherapy with a carbon ion boost improves local control and survival in high-risk sinonasal cancer with low toxicity.

## Contribution

First clinical outcomes of combined IMRT and carbon ions for sinonasal SCC with insights on neck management.

## Key findings

- OS and local progression-free survival at 12/24 months were 93.0%/89.3% and 88.4%/79.0%.
- Grade III toxicity occurred in 9.3% of patients with no grade IV events observed.
- Individualized neck treatment reduced radiation toxicity without compromising outcomes.

## Abstract

•Carbon ion boost with IMRT shows high local control in sinonasal SCC.•Node-negative neck management remains variable in sinonasal SCC treatment.•Treatment shows low grade III toxicity with no grade IV events observed.•First clinical outcomes of combined IMRT and carbon ions for sinonasal SCC.•Study supports individualized neck treatment to reduce radiation toxicity.

Carbon ion boost with IMRT shows high local control in sinonasal SCC.

Node-negative neck management remains variable in sinonasal SCC treatment.

Treatment shows low grade III toxicity with no grade IV events observed.

First clinical outcomes of combined IMRT and carbon ions for sinonasal SCC.

Study supports individualized neck treatment to reduce radiation toxicity.

Local control of high-risk sinonasal squamous cell carcinoma (SCC) remains challenging and often involves significant morbidity. Management of the node-negative neck is still debated. This study evaluated treatment outcomes, neck management strategies, and toxicity rates in patients treated with intensity-modulated radiotherapy (IMRT) combined with a carbon ion boost.

We evaluated 43 patients with sinonasal SCC treated with IMRT and carbon ion boost between 2011 and 2019. Follow-up followed head and neck cancer guidelines. Patient and tumor characteristics, treatment outcomes, and toxicity (per CTCAE v5.0) were assessed. Statistical analysis was performed using R version 4.1.0.

Median age was 64 years (range 19–83). Most patients had T3–4 tumors (n = 36; 83.7 %) and were clinically node-negative (n = 40; 93.0 %). The predominant regimen was 24 Gy (RBE) carbon ion boost in 8 fractions, followed by 50 Gy IMRT in 25 fractions. Postoperative RT was delivered to 25 patients (58.1 %), while 18 (41.9 %) received definitive RT. Elective or therapeutic neck dissection was performed in 10 patients (23.3 %), none showing lymph node metastases. In total, 22 distinct cervical lymph node treatment strategies were applied. Median follow-up for overall survival (OS) was 25.1 months. Tumor recurrence occurred in 11 patients (25.6 %), primarily due to local failure (n = 7; 63.6 %). OS and local progression-free survival (L-PFS) at 12/24 months were 93.0 %/89.3 % and 88.4 %/79.0 %, respectively. Grade III acute and late toxicity occurred in 9.3 % and 4.7 % of patients, respectively. No grade IV toxicity was reported. Mean numbers of grade I–II toxicities per patient were 4.8 (acute) and 2.4 (late).

IMRT with carbon ion boost provides promising OS and local control in high-risk sinonasal SCC. The management of the node-negative-neck was highly individualized. Toxicity was acceptable and may be further reduced by tailoring cervical lymph node treatment in selected patients.