3-DIMENSIONAL CONFORMAL RADIATION-THERAPY MAY IMPROVE THE THERAPEUTIC RATIO OF HIGH-DOSE RADIATION-THERAPY FOR LUNG-CANCER

Purpose: The specific aim of 3-dimensional conformal radiation therapy is to improve the target dose distribution while concomitantly reducing normal tissue dose. Such an approach should permit dose escalation until the limits of acceptable normal tissue toxicity are reached. To evaluate the feasibility of tumor dose escalation for nine patients with lung cancer, we determined the dose distribution to the target and normal tissues with 3-dimensional conformal radiation therapy and conventional planning. Methods and Materials: Plans were compared to assess adequacy of dose delivery to target volumes, dose-volume histograms for normal tissue, and normal tissue complication probabilities (NTCP) for nine patients with lung tumors. Results: The mean percentage of gross disease which received less-than-or-equal-to 70.2 Gy with 3-dimensional conformal radiation therapy (3DCRT) was 40% of the mean percentage of gross disease which received less-than-or-equal-to 70.2 Gy with conventional treatment planning (CTP). The mean NTCP for lung parenchyma with 3DCRT was 36% of the mean NTCP with CTP. The mean esophageal NTCP with 3DCRT was 88% of the mean NTCP with CTP. Conclusion: This preliminary analysis suggests that three dimensional conformal radiation therapy may provide superior delivery of high dose radiation with reduced risk to normal tissue, suggesting that this approach may have the potential to improve the therapeutic ratio of high dose radiation therapy for lung cancer.