The potential for dose escalation in lung cancer as a result of systematically reducing margins used to generate planning target volume.
OBJECTIVE
To determine how much the radiation dose to lung tumors could be increased as the margins used to generate planning target volume (PTV) are reduced.


METHODS
Treatment plans for 18 patients with non-small-cell lung carcinoma were retrospectively generated. Dose escalation was performed in two phases: The dose was increased as long as healthy tissue dose-volume constraints did not exceed (1) the values from the treatment plan originally used for the patients and (2) clinically acceptable values.


RESULTS
No correlation of dose escalation was observed with tumor location, tumor stage, tumor motion, and tumor volume. An increase in dose was observed for many of the patients with as little as 2-mm uniform reduction in PTV margin, with increases in mean PTV dose exceeding 15 Gy for 5 patients. Sixteen of 18 patients experienced a decrease in mean heart, esophagus, and lung dose when margins were reduced and prescription doses were increased.


CONCLUSIONS
Reduced margins allowed an increased dose to the tumors. However, a much larger dose escalation was possible for some patients but not for others, demonstrating that each patient is different, so individual treatment plans must be tailored for maximum tumor coverage and minimum exposure of healthy tissue.
Nelson
Christopher
C
Department of Radiation Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030, USA. cnelson@mdanderson.org
Starkschall
George
G
Chang
Joe Y
JY
D000368:Aged; D000369:Aged, 80 and over; D002289:Carcinoma, Non-Small-Cell Lung / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D008297:Male; D008875:Middle Aged; D009068:Movement; D011859:Radiography; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012119:Respiration; D012189:Retrospective Studies; D013679:Technology, Radiologic / Q000379:methods