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S.U. Din



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    O14 - Radiotherapy - Toxicity and Clinical Trials (ID 105)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      O14.03 - Using generalized equivalent uniform dose (gEUD) to model volume effects for brachial plexopathy after high-dose stereotactic body radiation therapy (SBRT) (ID 2835)

      10:30 - 12:00  |  Author(s): S.U. Din

      • Abstract
      • Presentation
      • Slides

      Background
      Brachial plexopathy is a rare but important toxicity of radiation therapy because of its significant impact on quality of life. For standard fractionated raiation therapy, good models of brachial plexus (BP) tolerance exist. However, the tolerance of the BP to SBRT is not well understood. We combined data from SBRT for apical lung and metastatic lesions near the BP spanning a wide range of doses and hypofractionation schemes. We determined the clinical incidence of brachial plexopathy and modeled the correlation with generalized equivalent uniform dose (gEUD) for both physical and biologically effective doses (BED) using a range of fractionation-sensitivity parameters (α/β) and volume effect parameters (a).

      Methods
      Between 2004 and 2012, 180 lesions (76 lung lesions and 104 metastatic lesions) located above the aortic arch and below the level of C3 were treated with SBRT. Patients with prior radiation therapy to this region were excluded. Metastases were treated to 14-30 Gy in 1-5 fractions and lung tumors to 22-60 Gy in 1-5 fractions. The BP was contoured per RTOG atlas definitions. For 54 centrally located spine metastases, both left and right BP were contoured and analyzed separately for a total of 234 BPs in 180 patients. Brachial plexopathy of ≥grade 1 (CTCAE v4.0) was the primary endpoint. Maximum dose to the BP (Dmax), minimum dose to the hottest 5% of the BP (D05), and their respective BEDs were calculated using α/β= 3 Gy. The gEUD was also calculated with the volume effect parameter (a) ranging from log~10~a= -1.0 to +1.0 in log~10~a steps of 0.1. A logistic regression model (LR) was fit to the data as a function of a. Clinical dose recommendations were derived with logrank tests using median splits.

      Results
      With median follow-up of 15.1 months, brachial plexopathy due to SBRT occurred in 9/234 BPs. Severity of brachial plexopathy was grade 1 in two, grade 2 in five and grade 3 in two patients. Median time to onset of brachial plexopathy was 6.2 months and the 1-/2-year actuarial rates were 3.3%/5.6%. For all patients the median BED for BP Dmax was 117.5 Gy and for D05 was 89.3 Gy. Median BED Dmax for patients with and without brachial plexopathy was 234 Gy and 115.2 Gy respectively (p=0.002). Brachial plexopathy was significantly associated with BP BED Dmax (p=0.002), and D05 (p=0.015), but not with physical dose. Using LR, the strongest correlation of gEUD with brachial plexopathy occurred for log~10~a= 1.0 using BED (p=0.002), which is representative of the BED Dmax. LR models of BED Dmax versus brachial plexopathy for various α/β values showed that any α/β<25 was a significantly better predictor than physical dose.

      Conclusion
      Brachial plexopathy is significantly associated with BED Dmax ≥117.5 Gy (equivalent to a physical dose of 17 Gy x1, 9.3 Gy x3 or 7 Gy x5 fractions) and D05 ≥89.3 Gy. BED Dmax was the most important predictor of this rare but serious toxicity.

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    P3.08 - Poster Session 3 - Radiotherapy (ID 199)

    • Event: WCLC 2013
    • Type: Poster Session
    • Track: Radiation Oncology + Radiotherapy
    • Presentations: 1
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      P3.08-013 - High local control rates with post-operative radiation therapy in incompletely resected non-small cell lung cancer (NSCLC) patients (ID 1659)

      09:30 - 16:30  |  Author(s): S.U. Din

      • Abstract

      Background
      Post-operative radiation therapy (PORT) is frequently given to patients with NSCLC who have microscopically positive margins (R1 resection) or gross residual disease (R2 resection) based on oncologic first principles. However, the data to support this practice is scarce. Here we report our institutional experience comparing patients who received PORT in the setting of R0, R1 or R2 resections.

      Methods
      Between 1999 and 2012, 203 patients with NSCLC were treated with PORT in 25-39 fractions to 45-70 Gy. All surgery and PORT were performed at our institution. Twenty-one patients had a sublobar resection, 158 had a lobectomy, and 24 underwent a pneumonectomy. PORT was given to R0 patients with pathologic N2 disease, R1 or R2 resections. Patients with negative margins were compared to patients with residual disease (R1 and R2 resections). Patients with tumor recurrence within the PORT field were recorded as local failures. Local failure-free survival (LFFS), disease-free survival (DFS) and overall survival (OS) were calculated using the Kaplan-Meier method. Univariate analysis was performed using the log-rank test.

      Results
      Fifty-five of 203 patients had residual disease after resection; 45 had R1 and 10 had R2 resections. The predominant histology was adenocarcinoma (80%). Stage at diagnosis was stage I-II in 17 patients, stage III in 186 patients. One-hundred and twenty-six (62%) patients received neoadjuvant and 39 (19%) adjuvant chemotherapy. Median age was 60 years and median KPS before PORT was 80. Median interval from surgery or adjuvant chemotherapy to PORT initiation was 1.6 months (range of 0-3.7 months). With a median follow up of 21 months, local failure occurred in 33/148 (22%) without and 14/55 (25%) patients with residual disease. Two- and 5-year actuarial LFFS rate were 79%/66% for R0 and 75%/58% for R1/R2 resections. Two- and 5-year actuarial DFS rate were 44%/30% for R0 and 48/26% for R1/R2 resections. Two-year and 5-year overall survival (OS) for all patients were 62.4% and 33.1%. LFFS, DFS and OS were not significantly different when comparing R0 to R1/R2 resections. Radiation dose, KPS, T-stage, N-stage, lymphovascular invasion, histology and chemotherapy were all not found to be significantly associated with any endpoint. OS was significantly worse for patients with R2 resection compared to R0/R1 resection (2-year OS 20% vs 64%; p= 0.002) and patients with age >65 (p=0.03). Multivariate analysis will be presented.

      Conclusion
      PORT results in equivalent local control rates after R1 and R2 resections when compared to R0 resections. This suggests that PORT has a significant role in local control of residual disease. However, OS was significantly worse for patients with gross residual disease postoperatively.