Clinical and Radiobiologic Effect of Partial Stereotactic Ablative Radiation Therapy in NSCLC

Abstract

Retrospectively evaluated the effect of Partial- Stereotactic ablative radiotherapy (P-SABR) in nonsmall cell lung carcinoma (NSCLC) and managed to evaluate the appropriate BED. Between December 2012 and September 2016 conditions for patient eligibility: (1)not suitable for surgery, because of being technically or medically inoperable or because of patient refusal; (2) histologic confirmation of NSCLC ;(3)no prior radiation therapy, interventional chemotherapy or radiofrequency ablation to the targeted area; (4) no prior chemotherapy or targeted therapy;(5) concurrent chemotherapy with DDP 50mg per week or no concurrent chemotherapy because not suitable; (6)complete follow-up image data in our hospital;(7)Karnofsky Performance Status >70; (8)minimum age 18 years; A total of 18 patients were included. The median period of follow-up was 12 months (range, 3–32 months). The median age was 64 years old(range, 40–85 years old).Squamous cell carcinoma was 66.7% (n=12), adeno carcinoma was 5.6% (n=1), other NSCLC was 27.8%(n=5). Among the patients, Stage II NSCLC was 16.7% (n =3), Stage III NSCLC was 38.9% (n =7), Stage IV NSCLC was 38.9% (n =7), local recurrence after operation was 5.6% (n =1). The median tumor diameter was 8.46 (5.04- 22.74cm). 66.7% (n=12) received RT alone.Dose prescription : conventional fractioned: A total dose of 44-60Gy in 16–33 fractions, 1.8-3Gy per fraction was administered with 6-MV X-rays in the PTV dose. SABR: A total dose of 18-32Gy in3-4fractions, 6-9Gy per fraction was administered in the GTV-boost dose. The median Tumor volume was 123.89cm3 (35.22- 495.50 cm3); The median GTV-boost volume was 24.90cm3 (8.13-115.90 cm3); Grade 3 or 4 radiaton pneumonitis(RTOG criteria) was observed in only two patients. The median overall survival was 16.3 month. The overall 1-year survival rates was 49%. The in-field 3-month and 1-year local contral(CR+PR)rates were 81.4% and 71.2%, respectively. The in-field 1-year local contral(CR+PR+SD)rates was 100%. We defined V100 as the ration of volume of BED>100Gy to the in-field tumor. The 1-year local control(CR+PR) rate was 90.9% for V100>30%, compared with 31.3% for V100<30% (p<0.05). We defined P75 as the ration of volume of physical dose >75Gy to the in-field tumor. The 1-year local control (CR+PR) rate was 90.9%for P75>40%, compared with 31.3% for P75<40% (p<0.05). Partial-Stereotactic ablative radiotherapy (P-SABR) in nonsmall cell lung carcinoma (NSCLC) was feasible and beneficial. 30% was a recommended ratio of the volume of BED>100Gy to the in-field tumor. 40% was a recommended ratio of the volume of physical dose >75Gy to the in-field tumor.