Clinical Experience of Three Dimensional Conformal Radiation Therapy for Non-Small Cell Lung Cancer

Choi, Eun Kyung; Yi, Byong Yong; Kang, One Chul; Nho, Young Ju; Chung, Weon Kuu; Ahn, Seung Do; Kim, Jong Hoon; Chang, Hyesook

Abstract

PURPOSE: This prospective study has been conducted to assess the value of three dimensional conformal radiation therapy (3DCRT) for lung cancer and to determine its potential advantage over current treatment approaches. Specific aim of this study were to 1) find the most ideal 3DCRT technique 2) establish the maximum tolerance dose that can be delivered with 3DCRT and 3) identify patients at risk for development of radiation pneumonitis.
MATERIALS AND METHODS
Beginning in Nov. 1994, 95 patients with inoperable non-small cell lung cancer (stage I; 4, stage II; 1, stage IIIa; 14, stage IIIb; 76) were entered onto this 3D conformal trial. Areas of known disease and elective nodal areas were initially treated to 45 Gy and then using 3DCRT technique 65 to 70 Gy of total dose were delivered to the gross disease. Sixty nine patients received 65 Gy of total dose and 26 received 70 Gy. Seventy eight patients (82.1%) also received concurrent MVP chemotherapy. 3DCRT plans were compared with 2D plans to assess the adequacy of dose delivery to target volume, dose volume histograms for normal tissue, and normal tissue complication probabilities (NTCP).
RESULTS
Most of plans (78/95) were composed of non-coplanar multiple (4-8) fields. Coplanar segmented conformal therapy was used in 17 pateints, choosing the proper gantry angle which minimize normal lung exposure in each segment. 3DCRT gave the full dose to nearly 100% of the gross disease target volume in all patients. The mean NTCP for ipsilateral lung with 3DCRT (range ; 0.17-0.43) was 68% of the mean NTCP with 2D treatment planning (range ; 0.27-0.66). DVH analysis for heart showed that irradiated volume of heart could be significantly reduced by non-coplanar 3D approach especially in the case of left lower lobe lesion. Of 95 patients evaluable for response, 75 (79%), showed major response including 25 (26%) with complete responses and 50 (53%) with partial responses. One and two year overall survivals of stage lll patients were 62.6% and 35.2% respectively. Twenty percent (19/95) of patients had pneumonitis ; Eight patients had grade 1 pneumonitis and 11 other patients had grade 2. Comparison of the average of NTCP for lung showed a significant difference between patients with and without radiation pneumonitis. Average NTCP for patients without complication was 62% of those with complications.
CONCLUSIONS
This study showed that non-coplanar multiple fields (4-8) may be one of the ideal plans for 3DCRT for lung cancer. It also suggested that 3DCRT may provide superior delivery of high dose radiation with reduced risk to normal tissue and that NTCP can be used as a guideline for the dose escalation.