Correlations between the irradiated dose to lymph node regions and lymph node recurrence when involved field radiotherapy used for limited-stage small cell lung cancer / 中华放射医学与防护杂志

ABSTRACT

Objective To analyze the relationship between the radiation doses to mediastinal lymph nodes regions and the regional failure patterns when involved field radiation therapy (IFRT) was used for limited-stage small cell lung cancer (SCLC).Methods The mediastinal lymph node regions (group 1 to 10) of the iimited-stage SCLC patients received definitive radiotherapy were contoured in treatment planning system.The intentional or incidental radiation doses to each lymph node regions were recorded.In-field recurrence,marginal recurrence and out-of-field recurrence were respectively defined as the volume of failed lymph nodes located within the 80％ iso-dose lines,in the 80％-20％ iso-dose lines and beyond the 20％ iso-dose lines of prescribed doses.Results A total of 1 216 lymph node regions in 76 patients were contoured.The median follow-up time was 17.4 months.At diagnosis,lymph node regions with metastatic rates ＞50％ were 4R (68.7％),4L (57.9％),10R (57.9％),2R (56.6％) and 7 (51.3％).The positive lymph node regions were all subjected to prescribed doses.The lymph node regions that received incidental radiation doses of more than 3 000 cGy were3P,4L,7,6,4R,5,2L.The median lymph node failure-free time was 9.8 months.In this study,only 1 patient developed out-of-field mediastinal lymph nodes failure.The rest of out-of-field recurrences and marginal recurrences were developed in the supraclavicular regions or contralateral hila.Conclusions When IFRT is used to treat mediastinal lymph node regions for patients with SCLC,negative mediastinal regions can be subjected to considerable incidental radiation doses.Out-of-field recurrences of the mediastinal lymph node regions are rare.This is contributed by the incidental radiation dose to these regions.