Adaptive Planning in Intensity-Modulated Radiation Therapy for Head and Neck Cancers: Single-Institution Experience and Clinical Implications

• DOI: 10.1016/j.ijrobp.2010.03.014
• Publication Date: 2010-07-11T23:54:56Z
• Authors: Peter H. Ahn; Chin-Cheng Chen; Andrew I. Ahn; Linda Hong; Paola G. Scripes; Jin Shen; Chen-Chiao Lee; Ekeni Miller; Shalom Kalnicki; Madhur K. Garg
• Keywords: Organs at Risk; Radiotherapy Planning, Computer-Assisted; Radiotherapy Dosage; Patient Positioning; Tumor Burden; 3. Good health; 03 medical and health sciences; 0302 clinical medicine; Spinal Cord; Head and Neck Neoplasms; Carcinoma, Squamous Cell; Humans; Parotid Gland; Radiotherapy, Intensity-Modulated; Tomography, X-Ray Computed

Anatomic changes and positional variability during intensity-modulated radiation therapy (IMRT) for head and neck cancer can lead to clinically significant dosimetric changes. We report our single-institution experience using an adaptive protocol and correlate these changes with anatomic and positional changes during treatment.Twenty-three sequential head and neck IMRT patients underwent serial computed tomography (CT) scans during their radiation course. After undergoing the planning CT scan, patients underwent planned rescans at 11, 22, and 33 fractions; a total of 89 scans with 129 unique CT plan combinations were thus analyzed. Positional variability and anatomic changes during treatment were correlated with changes in dosimetric parameters to target and avoidance structures between planning CT and subsequent scans.A total of 15/23 patients (65%) benefited from adaptive planning, either due to inadequate dose to gross disease or to increased dose to organs at risk. Significant differences in primary and nodal targets (planning target volume, gross tumor volume, and clinical tumor volume), parotid, and spinal cord dosimetric parameters were noted throughout the treatment. Correlations were established between these dosimetric changes and weight loss, fraction number, multiple skin separations, and change in position of the skull, mandible, and cervical spine.Variations in patient positioning and anatomy changes during IMRT for head and neck cancer can affect dosimetric parameters and have wide-ranging clinical implications. The interplay between random positional variability and gradual anatomic changes requires careful clinical monitoring and frequent use of CT- based image-guided radiation therapy, which should determine variations necessitating new plans.