Retrospective Analysis Of Target Delineation In Recurrent Small Cell Lung Cancer

Objective:To retrospectively analyze the relationship of target delineation in localrecurrence of small cell lung cancer radiotherapy with related factors of recurrence,dosimetry and toxic and side reaction.Materials:In this study41local recurrence (with or without distant metastasis) casesof patients with small cell lung cancer were collected from2010January to2013June in Jilin Province Tumor Hospital. According to the target delineation inradiotherapy range the patients were divided into the observation (GTV afterchemotherapy remained the primary tumor and lymph node in22cases) and controlgroups (GTV before chemotherapy in19patients with metastatic lymph nodes).Methods:After the posture of fix and CT scanning, we draw the outline of target andorgan at risk: GTV, CTV and PTV sketches were drawn by referencing the enhancedchest CT or PET-CT in the patients before and after chemotherapy according to theICRU50and ICRU62report. GTV was drawn according to remaining the primarytumor and lymph node or tumor bed sketches after chemotherapy in the observationgroup, and it was done by imaging of primary tumor and lymph nodemetastasis range sketches displayed before chemotherapy in the control group. Thepositive lymph nodes in two groups were≥1.0cm lymph nodes of CTscanning. CTV range was external0.5-0.8cm in GTV+positive lymph noderegion. PTV range was extending0.8-1.0cm in four sides and extending1.0-1.5cm upand down direction in CTV according to the patient respiratory motion and positionerror. Sketching the organs at risk included the spinal cord, esophagus, lung, heart and liver. The prescription doses were40-54Gy/4-6weeks,1.8-2.0Gy/time,1time/day,5times/week.Results:1. The relapsed patients in the observation and control groups were15(68.2%) and14cases (73.7%) in the radiation field respectively, and ones were7(31.8%) and5cases (26.3%) out irradiation field respectively.. The median time ofrelapsed patients in the observation group was11months, and12months in thecontrol group (P>0.05).2. The mean lung dose (MLD) and pulmonary V20valuesof patients in the observation group were significantly lower than those in the controlgroup (P=0.01);3. The incidence rate of acute radioactive pneumonia was13.6%inthe observation group with>5%weight loss to reach to22.7%, while that in thecontrol group was57.9%(P <0.047and0.023). The incidence rate in hematologictoxicity of> grade Ⅲ during radiotherapy in the observation group was13.6%, and that in late radiation lung injury of grade Ⅰ-Ⅱin the control group was4.5%, that the hematological toxicity3level and above was21.1%, and that inlate radiation lung injury of grade Ⅰ-Ⅱ was15.8%(P values were0.129and0.249).there was no radioactive lung injury of spinal cord reaction of petients in the twogroups, no advanced level of grade Ⅲ.Conclusion:This retrospective analysis shows that only irradiation after chemotherapy ofprimary tumor and positive lymph node region range did not affect the local controlrate, and reduce the toxicity of radiotherapy. So the study is retrospective analysisto need more samples of evidence-based learning support in the perspective study.