Adaptive planning in intensity-modulated radiation therapy for head and neck cancers: single-institution experience and clinical implications.
OBJECTIVE
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.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Ahn
Peter H
PH
Department of Radiation Oncology, Montefiore Medical Center and Albert Einstein College of Medicine of Yeshiva University, Bronx, New York 10467, USA.
Chen
Chin-Cheng
CC
Ahn
Andrew I
AI
Hong
Linda
L
Scripes
Paola G
PG
Shen
Jin
J
Lee
Chen-Chiao
CC
Miller
Ekeni
E
Kalnicki
Shalom
S
Garg
Madhur K
MK
D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006258:Head and Neck Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D058958:Organs at Risk / Q000000981:diagnostic imaging / Q000528:radiation effects; D010306:Parotid Gland / Q000000981:diagnostic imaging / Q000528:radiation effects; D056888:Patient Positioning; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D013116:Spinal Cord / Q000000981:diagnostic imaging / Q000528:radiation effects; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden