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TU_26_3571 - Partial Stereotactic Ablative Boost Radiation Therapy In Bulky NSCLC

Tuesday, October 23
2:45 PM - 4:15 PM
Location: Innovation Hub, Exhibit Hall 3

Partial Stereotactic Ablative Boost Radiation Therapy In Bulky NSCLC
Y. Bai, X. GAO, S. Qin, J. Chen, and M. Su; Department of Radiation Oncology, Peking University First Hospital, Beijing, China

Purpose/Objective(s): Bulky non-small cell lung cancer (NSCLC) is difficult to achieve effective local control by conventional radiotherapy (CRT). The present work aims to evaluate the safety and efficacy of partial stereotactic ablative boost radiotherapy (P-SABR) in bulky NSCLC.

Materials/Methods: From Dec 2012 through Aug 2017, 30 patients with bulky NSCLC treated with P-SABR technique were analyzed. The P-SABR plan consisted of one partial SABR plan (5-9 Gy/f, 3-6 fractions) to gross tumor boost (GTVb) followed by one conventional plan to the planning target volume (PTV). GTVb was the max volume receiving SABR to guarantee the PTV margin dose falloff to about 3 Gy/f. And the total dose of PTV margin was planned to about 64Gy. The simply CRT plans were created using the same planning parameters as the original plan, with the goal to achieve comparable organs-at-risks (OARs) doses and PTV margin dose to P-SABR plan. Dosimetric variables were acquired in both P-SABR and compared CRT plans. Toxicity, local control and survival were also evaluated.

Results: 27 patients (90%) were male, 3 patients (10%) was female. Median age at treatment was 64.5 years (40 to 85 years). 26 patients were pathologically diagnosed as having NSCLC. 3 patients (10%) had stage IIB(T3N0M0), 9 patients (30%) had stage IIIA, 6 patients (30%) had stage IIIB and 12 patients (40%) had stage IV. Median volume of the tumor treated by P-SABR was 138.07cm3(25.55 to 495.50 cm3) with a median maximal diameter of 8.08cm (4.62 to 14.64 cm). Median follow up-was 9.5 months (range 2.2-39.4 months). No severe acute side effects >CTCAE Grade III were observed. 1-year overall survival was 88.2%. 2-year overall survival was 55.6%. Local response was achieved in 27 of these 30 patients (90%). 11 patients (36.7%) had PR, 10 patients (33.3%) had SD and 9 patients (30%) had PD. 7 patients (23.3%) had local response but systemic progression and 3 patients (10%) presented with a RT-in-field-progression. 1-year local control rate was 100%.2-year local control rate was 85.7%. Patients with B90≥65% achieved higher local control rate than those with B90<65% (p=0.010). P-SABR had significantly higher HI index (p<0.001), while the similar CI index (p>0.5). No differences were found in Dmin and D98 of PTV between P-SABR and the simply CRT plans (p>0.1). Compared to the conventional plan, P-SABR plans increased dose at the isocenter, BED at the isocenter, Dmean and Dmax by 17.89%,26.31%, 7.75% and 14.39%, respectively(p<0.001). We define B80 as the ration of volume of BED>80Gy to the in-field tumor. B80, B90, B100, B110, B120, V65, V70, V75 and V80 were improved by 27.91%, 74.11%, 96.10%, 99.90%, 100.00%, 33.72%, 61.64%, 68.54% and 80.51% in P-SABR plan(p<0.05).

Conclusion: P-SABR is feasible and well tolerated in bulky NSCLC. Local control rate is encouraging, especially for B90≥65% group, which may due to the ability of P-SABR to optimize BED with equivalent toxicity.

Author Disclosure: Y. Bai: None. J. Chen: None. M. Su: None.

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TU_26_3571 - Partial Stereotactic Ablative Boost Radiation Therapy In Bulky NSCLC

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