Prospective Controlled Trial Of Body Gamma Knife With Different Fractionation For Tumor Metastasis In Lung

Objective: There is one of the most common blood circular transfer position of themalignant advanced tumor in lung. Lung metastases account for1/5-1/2of cancerdeaths. General treatments of pulmonary metastases include surgery, chemotherapy andradiotherapy. Other methods include biological immune therapy, interventionalradiofrequency ablation, radioactive particles implantation, etc. Chemotherapy isapplied much frequently for lung metastases. But most patients give up treatmentbecause of progress or untolerate. Operation treatment has contraindications and morestrict requirements. Not only in the psychological and physical are patients hard toaccept, but also there are relatively large on operation risk and complications.Due to the limitation of irradiation technology, there is difficult to improve singledose and total dose, and is poor efficacy and side effects in conventional radiotherapy.Therefore, the above treatments have great limitations in the cure of pulmonarymetastasis. Developing in recent10years, Gamma ray stereotactic radiotherapy (gammaknife, γ-knife) have some characteristics including concentrated dose in target area andthe less dose in normal tissue around target area. Meanwhile, this technique is lessaffected by tumor tissue itself radiosensitivity，suitable for small volume lesionsregardless of different pathological types. There is less prospective study and no unifieddose mode on gamma knife radiotherapy of lung metastasis tumor at present. Observethe efficacy and side effects of different segmentation dose mode during body gammaknife radiotherapy in lung metastases and the idea time dose segmentation model wasinvestigated on body gamma knife treatment of pulmonary metastases in the study.Methods:100patients with lung metastases were enrolled on2008April to2012August in radiation oncology department of Air Force General Hospital. There were 199pulmonary metastases. According to the total irradiation dose, all patients weredivided into50Gy group and40Gy group. The vacuum bag was used to fix position.Use the supine or prone position according to the location of patient’s pulmonarymetastatic tumor. CT simulation was implemented by CT scanning machine. Everyslice needed5seconds and slice thickness was5mm. Position location was determinedand line markers were painted on the body surface by3D laser positioning system.Then the images were transferred to the planning system and delineation of target areawas finished by physicians on position image. The50%isodose line was defined atprescription dose line in the two groups. The irradiation dose was5Gy and4Gyrespectively. The total fractions were10times,1times/day,5times per week. Patientsshould be back to hospital and examined for CT every3months after treatment.Results: There were CR46.23%(92/199), PR45.22%(90/199), SD6.03%(12/199),PD2.01%(4/199),CR+PR91.46%(182/199) in100cases. The overall one year and twoyears local control rate was respectively97.8%and94.5%. There were95metastases in50Gy group, CR49.47%(47/95), PR43%(45/95), SD4.21%（4/95）, PD0%(0/95),CR+PR94.74%(92/95). The control rates of one year and two years were respectively100%and97.9%. There were104metastases in40Gy group, CR43.27%(45/104), PR47%(47/104), SD7.69%(8/104), PD3.85%(4/104), CR+PR88.46%(92/104),respectively.9cases with diameter＜1cm were CR. The overall survival rates of oneyear and two years were respectively86.7%and67.9%in all patients. The survivalrates of one year and two years were respectively91.9%and78.9%in50Gy group. Thesurvival rates of one year and two years were respectively72.6%and48.4%in40Gygroup. Local control rate and survival rate in50Gy group were significantly higher thanin group40Gy (p value0.036and0.006, respectively).Conclusion: Body gamma knife is an effective method in treatment of lungmetastases. Local irradiation dose is associated with local control rate and survival rate.Radiotherapy dose mode with50Gy/10times,5times/week at50%isodose line hasbetter local control rate and survival rate than with40Gy/10time. The dose model with 40Gy/10times/two week is expected to be good local control for the pulmonarymetastases with diameter<1cm.