PV QA 4 - Poster Viewing Q&A 4
Purpose/Objective(s): Prior randomized data have shown a lack of benefit to dose escalated radiotherapy (RT) for locally advanced NSCLC to 74 Gy delivered in 37 fractions. The purpose of this analysis was to evaluate the early treatment outcomes and toxicities for dose escalated RT using a simultaneous integrated boost (SIB) technique to 70 Gy in 30 fractions.
Materials/Methods: 43 patientswith clinical stage IIA (14%), IIB (9%), IIIA (58%), and IIIB (19%) underwent RT using an SIB technique with concurrent chemotherapy between April 2016 and October 2017 at a single institution. The mean age was 71.2 years (53-90), with 49% male (N=21), 51% female (N=22) and a majority were ECOG 0-1 (90%). Among the patients, 23% had T1 (N=10), 33% had T2 (N=14), 37% had T3 (N=16), 5% had T4 (N=2) and 2% had Tx (N=1) lesions. Histologically, a majority were either SCC (42%) or adenocarcinoma (47%) with adenosquamous (7%), sarcomatoid (2%) or large cell (2%) comprising the rest. All patients underwent 4D planning CT to generate a GTV_ITV to account for organ motion and were treated with daily online image-guidance using cone-beam CT. A 5mm GTV to CTV and 5mm CTV to PTV expansion was employed. Plans were generated using either IMRT or VMAT. Planning goals were to deliver 70 Gy in 30 fractions (2.33 Gy/fx) to the GTV_ITV with 60 Gy to the CTV and PTV (2 Gy/fx). Recurrence and survival outcomes were analyzed using the Kaplan-Meier method. Treatment-related pneumonitis and esophagitis were graded according to CTCAE 4.0. Median follow-up time was 9.7 months (2-21 months).
Results: The median GTV_ITV mean dose was 73.4 Gy (58.6-77.7 Gy). The median GTV_ITV D95 was 70.6 Gy and D99 was 69.6 Gy. Median PTV mean dose was 68 Gy (54.8-71.8 Gy). The median mean lung dose (Lungs–GTV) was 15 Gy (2.7-22.3 Gy); median lung V5 and V20 were 59% and 24%, respectively (13-85.8%; 3.4-36%). The median Dmax for esophagus was 70.5 Gy (9.95-77.9 Gy); and the median mean esophageal dose was 20.7 Gy (1.66-40.7 Gy). The median mean heart dose was 9.15 Gy (0.1-35 Gy). The median Heart V5, V20, V30, and V50 were, 34.2%, 15.6%, 9.99%, and 3.33%, respectively. The median overall survival (OS) was not reached. The 3mo, 6mo, 12mo, and 18mo OS and cause specific survival (CSS) were 91%, 83%, 76% and 63%; and 98%, 92%, 84% and 78%, respectively. The rates of local recurrence (LR), regional recurrence (RR) and distant metastasis (DM) are depicted in Table 1. Grade 2 or higher pneumonitis occurred in 25.6%, with 58%, 16.3%, 9.3%, and 0% grade 1, 2, 3, or 4/5. Grade 2 acute esophagitis occurred in 63% of patients, with no grade 3 or higher toxicity. Chronic grade 1 esophagitis was noted in 16% of patients, with no grade 2 or higher chronic toxicity.
Conclusion: Dose escalation was achievable using this SIB technique while limiting normal tissue dose volume constraints to be within current RTOG and national guidelines, particularly with respect to the heart and lung. Early toxicity, recurrence and survival outcomes were promising.
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