Objectives: To evaluate the necessity of adaptive planning in helical tomotherapy (TOMO) for head and neck cancer in terms of dosimetric influence on the parotid gland.
Methods: Thirty-one patients underwent curative TOMO for head and neck cancer from April 2006 to April 2007. For each patient, neck diameter was monitored together with body weight at first cervical spine level through mega-voltage computed tomography during the TOMO course. Ten of 31 patients, with significant weight loss (>5%) and/or neck diameter decrease (>10%), were selected for dosimetric analysis, and parotid dose was recalculated at the fourth and last week of TOMO. Xerostomia was estimated by Radiation Therapy Oncology Group criteria.
Results: The median dose was 69.96 Gy (range, 54 to 69.96 Gy) and there was no grade 3 or greater complication. Ten patients with significant neck diameter decrease and/or weight loss showed frequent grade 2 acute xerostomia (P=0.02). The volume percentage of daily fractional dose over 0.75 Gy for the parotid gland (V0.75 Gy) increased by 23.6% at the end of TOMO.
Conclusions: For patients with significant anatomic contour change; neck diameter decrease (>10%) or weight loss (>5%), adaptive planning using mega-voltage computed tomography can identify dosimetric changes and reduce deleterious side effects such as xerostomia.