Lung Cancer

PV QA 4 - Poster Viewing Q&A 4

TU_32_3631 - A Method for Analyzing and Reporting Patterns of In-Field Recurrence after Definitive Concurrent Chemoradiation in Locally Advanced Non-Small Cell Lung Cancer

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

A Method for Analyzing and Reporting Patterns of In-Field Recurrence after Definitive Concurrent Chemoradiation in Locally Advanced Non-Small Cell Lung Cancer
S. Gandhi1, C. Nantavithya1,2, J. Y. Chang1, S. H. Lin1, Z. Liao1, A. S. Mohamed1, C. D. Fuller1, H. Li1, and D. R. Gomez1; 1The University of Texas MD Anderson Cancer Center, Houston, TX, 2King Chulalongkorn Memorial Hospital, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand

Purpose/Objective(s): We describe a novel method for analyzing and reporting patterns of in-field recurrence after definitive concurrent chemoradiation for locally advanced non-small cell lung cancer (LA-NSCLC). Our method incorporates geometric information from diagnostic images at recurrence as well as dosimetric variables from the initial treatment plan to provide a standardized classifier of in field failures.

Materials/Methods: Scans from patients with stage II-III NSCLC who had a local recurrence after definitive concurrent chemoradiation with radiation dose ≥ 60 Gy were analyzed. The recurrent gross tumor volume (rGTV) and centroid (geometric center of recurrent lesions) were delineated manually from diagnostic CT images at recurrence. The diagnostic CT images at recurrence were registered first by rigid registration with the initial treatment planning images and radiation dose images followed by deformable image registration. Only patients with in field recurrence (centroid originated within original planning target volume (PTV)) were included in our analysis. Dose-volume histograms for each rGTV were used to classify in-field recurrences as central high-dose recurrence, type A (defined as dose to 95% of the rGTV [rGTVD95%] was ≥95% of the prescription dose to PTV) or peripheral high-dose recurrence, type B (rGTVD95% was <95% of the prescription dose to PTV).

Results: Of the 62 , 33 patients showed an in-field recurrence of which 5 cases received three dimensional conformity radiotherapy technique, 15 patients received intensity modulated radiotherapy and 13 cases received passive scattering proton beam therapy. Median prescribed radiation dose was 66 Gy. Twenty six patients had type A recurrence, 6 patients had type B recurrence and 1 patient had two separate lesions, type A and type B recurrence. Tumors that were prescribed 60-70 Gy were statistically more likely to have type A failures while tumors that were prescribed >74 Gy were more likely to have type B failures (p=0.028). The median prescribed dose to tumors with type A recurrences was lower than type B recurrences, 70 and 74 Gy respectively (p = 0.025). However, median dose to 95% of rGTV (rGTVD95%) for type A recurrences was statistically higher than type B recurrences, 70.59 Gy and 50.59 Gy, respectively (p = 0.001). No statistical differences of radiation techniques, time to recurrence, rGTV size and other DVH results were seen between type A and B recurrences.

Conclusion: We report a standardized method for analysis and classification of in-field recurrence after definitive concurrent chemoradiation for LA-NSCLC. The results showed more central high dose, type A recurrences, than peripheral high dose, type B recurrences, suggesting biological causes such as radioresistence rather than technical issues as mechanisms of in-field recurrence.

Author Disclosure: S. Gandhi: None. C. Nantavithya: None. J.Y. Chang: Research Grant; MDACC-BMS Alliance Research Grant. Partnership; Global Oncology One. Chair of the Board of Directors; SANTRO. Chair; ACR. Chair for Thoracic Subcommittee; PTCOG. S.H. Lin: Research Grant; Roche/Genentech, Peregrine Pharmaceuticals, Inc, Hitachi Chemical, Inc. Z. Liao: Chair; ASTRO IES. A.S. Mohamed: None. C.D. Fuller: Research Grant; National Institutes of Health, National Science Foundation, Elekta AB. Grant funding; Elekta AB. Honoraria; Nederlandse Organisatie voor Wetenschappelijk Onde. Consultant; Elekta AB, Nederlandse Organisatie voor Wetenschappelijk Onde. Travel Expenses; Elekta AB, Nederlandse Organisatie voor Wetenschappelijk Onde. Reviewer; Radiological Society of North America. Associate Editor; Radiographics. Data Management Task Force Committee Member; MR-LinAc Consortium. Member; National Cancer Institute. Task Group Member; American Association of Physicists in Medicine. H. Li: Research Grant; Varian Medical Systems. D.R. Gomez: Research Grant; AstraZeneca, Merck, BMS. Honoraria; Varian, Merck, BMS. Advisory Board; AstraZeneca.

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TU_32_3631 - A Method for Analyzing and Reporting Patterns of In-Field Recurrence after Definitive Concurrent Chemoradiation in Locally Advanced Non-Small Cell Lung Cancer



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