Volume or position changes of primary lung tumor during (chemo-)radiotherapy cannot be used as a surrogate for mediastinal lymph node changes: the case for optimal mediastinal lymph node imaging during radiotherapy.
OBJECTIVE
Primary lung tumors can be visualized mostly with cone beam computed tomography (CT), whereas visualization is much more difficult for mediastinal lymph nodes (LN). If the volumetric and positional changes of the primary tumor could be used as a surrogate for the LN, this would facilitate image-guided radiotherapy. The purpose of this study was to investigate the relationship between the positional and volumetric changes in primary tumors and the involved LN during (chemo)radiotherapy treatment of non-small-cell lung cancer patients.


METHODS
[(18)F]fluorodeoxyglucose positron emission tomography/computed tomography imaging was performed before radiotherapy and in the second week of treatment in 35 patients. Gross tumor volumes (GTV) of the primary tumor (GTVprim) and of the involved LN (GTVlymph) were delineated. Changes in position and volume of GTVprim with respect to GTVlymph and the bony anatomy were compared.


RESULTS
In individual cases, large displacements up to 1.6 cm and volume changes of 50% of the primary tumor may occur that are not correlated to the changes in involved LN. The volume of GTVprim reduced, on average, by 5.7% ± 19.0% and was not correlated with the small increase of 1.4% ± 18.2% in involved LN volume. Compared to bony anatomy, displacement of the primary tumor was statistically correlated to the involved LN displacement.


CONCLUSIONS
Volume and position changes of the primary tumor are not always predictive for LN changes. This suggests that for characterization of involved LN, repeated state-of-the-art mediastinal imaging during radiotherapy may be necessary.
van Elmpt
Wouter
W
Department of Radiation Oncology MAASTRO, GROW-School for Oncology and Developmental Biology, Maastricht University Medical Centre, Maastricht, The Netherlands. wouter.vanelmpt@maastro.nl
Ollers
Michel
M
van Herwijnen
Henrieke
H
den Holder
Linda
L
Vercoulen
Lindsay
L
Wouters
Monique
M
Lambin
Philippe
P
De Ruysscher
Dirk
D
D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D003131:Combined Modality Therapy / Q000379:methods; D005260:Female; D019788:Fluorodeoxyglucose F18; D056973:Four-Dimensional Computed Tomography / Q000379:methods; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000188:drug therapy / Q000473:pathology* / Q000532:radiotherapy; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000473:pathology*; D008297:Male; D008482:Mediastinum; D008875:Middle Aged; D009068:Movement; D049268:Positron-Emission Tomography / Q000379:methods; D011446:Prospective Studies; D019275:Radiopharmaceuticals; D011879:Radiotherapy Dosage; D047368:Tumor Burden / Q000187:drug effects / Q000528:radiation effects
D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18