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Strategy for dose escalation using 3-dimensional conformal radiation therapy for lung cancer
Authors:Armstrong, J. G.   Zelefsky, M. J.   Leibel, S. A.   Burman, C.   Han, C.   Harrison, L. B.   Kutcher, G. J.   Fuks, Z. Y.
Affiliation:1Departments of Radiation Oncology, Memorial Sloan-Kettering Cancer Center New York, NY, U.S.A.
2Departments of Medical Physics, Memorial Sloan-Kettering Cancer Center New York, NY, U.S.A.
Abstract:PURPOSE: Local failure is a major obstacle to the cure of locally advancednon-small-cell lung cancer. 3-Dimensional conformal radiationtherapy (3-DCRT) selects optimal treatment parameters to increasedose to tumor and reduce normal tissue dose, potentially permittingdose escalation. There are several ongoing trials of dose escalationusing 3-dimensional conformal radiation therapy for non-small-celllung cancer. We performed this analysis to determine if dataderived from dose volume histograms could be used as the basisfor designing the method of dose escalation in these trials. METHODS AND MATERIALS: Between 1990 and 1993, 31 patients were treated with 3-DCRTand had complete normal tissue dose volume histograms createdas part of the planning process. The stage distribution wasstage I/TI 13%, stage IHa in 45%, and stage Illb in 42%. Themedian radiation dose to gross disease was 70.2 Gy (52.2–;72Gy). Elective mediastinal irradiation (50.4 Gy) was administeredto 52% (16/31) of patients. RESULTS: Thr toxicity encountered in this experience was pulmonary. Dose-volume-histogramdata were used to analyze the predictors of toxicity and showeda correlation between risk of pulmonary toxicity and indicesof dose to lung parenchyma. Grade 3 or higher pulmonary toxicityoccurredin 38% (3/8) of pts with > 30% of lung volume receiving >25 Gy, versus 4% (1/23) of pts. with < 30% lung receiving> 25 Gy (p =0.04). Grade 3 or higher pulmonary toxicity occurredin 29% (4/14) of patients with a predicted pulmonary normaltissue complication probability of 12% or higher versus 0% (0/17)in patients with a predicted probability of less than 12% (p=0.03).The single fatality occurred in a patient with a calculatedpneumonitis probability of 85% and a high percent (49%) lungvolume receiving > = 25 Gy. CONCLUSION: This preliminary experience demonstrates a correlation betweenlung dose-volume-histogram data and the risk of severe pulmonarytoxicity. This provides an opportunity to modify the methodof radiation dose escalan. Dose-volume-histogram data can allowescalation according to the risk to the lung parenchyma (whichis the major organ of concern) rather than escalation accordingto tumor dose levels. Because of the major inter-patient variabilityof intrathoracic tumor bulk and anatomic distribution, thisstrategy is intuitively appropriate. This approach may facilitatecompletion of dose escalation studies and identification ofmaximum tolerable pulmonary dose levels. lung cancer, radiation, 3-dimensional treatment planning
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