Feasibility of transitioning to marker-less immobilisation using optical surface guidance in head and neck cancer treatment: a study at territory state cancer centre in a developing country.

PURPOSE/OBJECTIVES: In countries such as India, where a large share of cancer patients undergoes head and neck radiotherapy, setups still rely primarily on laser alignment with surface markers on the mask. This study explores transitioning from conventional marker-based setup to markerless setups using optical surface guidance (SGRT) to determine if treatment accuracy can be maintained particularly in a territory state cancer centre setting where resources are limited.

MATERIALS/METHODS: A prospective study of 80 head-and-neck cancer patients, randomized into two groups was performed: open-face mask group (OM) with optical surface guidance (AlignRT) versus conventional masks with surface-marker setup. All received Volumetric Modulated Arc Therapy VMAT (60-70 Gy in 30-35 fractions). Cone Beam Computed Tomography (CBCT) verified positioning, and translational/rotational shifts were used to calculate systematic (Σ) and random (σ) errors. Group differences were analyzed with an independent t-test.

RESULTS: Translational setup errors in both OM and CM systems were consistently below 0.2 cm across all axes, with no statistically significant differences observed (p > 0.05). Rotational deviations in pitch, roll, and yaw were generally within 1°, with OM showing slightly improved stability trends compared to CM. Weekly error analysis confirmed stable reproducibility better in OM group compared to the CM over the treatment course.

CONCLUSION: The open-face mask with optical surface guidance is a feasible alternative to conventional closed-face masks in head and neck cancer treatment. It offers comparable accuracy, lateral axis advantage and comparable precision in vertical and longitudinal axes. It enhances patient comfort without increasing imaging frequency or margins and improves treatment outcomes.