Author of

• 20193

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  P3.14 - Radiotherapy (ID 730)

  • Event: WCLC 2017
  • Type: Poster Session with Presenters Present
  • Track: Radiotherapy
  • Presentations: 1
  • Moderators:
  • Coordinates: 10/18/2017, 09:30 - 16:00, Exhibit Hall (Hall B + C)

  • 24203

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    P3.14-013 - Outcomes According to Marginal Tumor Dose Prescription for Small- to Medium-Sized Brain Metastases from Lung Cancer (ID 10416)

    09:30 - 09:30  |  Author(s): B. Millar
    • Abstract
    • Slides

    Background:
    At our institution, we commonly treat brain metastases (BM) adjacent to critical structures with a smaller dose prescription (DP) to reduce the likelihood of toxicity. We sought to evaluate the impact of DP on LF and RN for small- to medium-sized BM (≤ 2 cm) from lung cancer.
    
    Method:
    A prospective registry of BM patients treated with gamma knife SRS between 2008 and 2016 was interrogated to determine per lesion rates of LF and RN. Each lesion was followed until LF or RN or at last MRI follow-up. Defined criteria were used to differentiate LF from RN. Whole brain irradiation (WBI) was a censoring event.
    
    Result:
    From 1,465 potential subjects, 345 small- to medium-sized BM from 151 lung cancer patients were evaluated. Median radiographic follow-up was 10.2 months. Median lesion volume and diameter were 0.17 cm[3], and 0.81 cm, respectively. The DP for 71 lesions (21%) was 15 Gy, and ≥ 20 Gy (median 21 Gy; 20-24Gy) for 274(79%). Most lesions were ≤ 1 cm (65%). Median number of SRS was 2 (1-4) and 36 patients received salvage WBI. Sixteen lesions (4%) developed LF and 12 (3%) developed RN. Freedom from local failure at 1 year (FFLF) for 15 Gy, and ≥ 20 Gy, was 80%, and 95%, respectively (p=0.02). FFLF for lesions ≤1cm, and >1 cm, was 95%, and 78%, respectively (p<0.01). Freedom from RN at 1-year (FFRN) for DP 15 Gy, and ≥ 20 Gy, was 98%, and 96%, respectively (p=0.3). FFRN for lesions ≤ 1cm, and > 1 cm, was 98%, and 93%, respectively (p=0.01). FFLF and FFRN for lesions ≤1 cm and >1 cm, according to DP, are shown in Table 1.

    	Lesion size
    	≤1 cm		P value	>1 cm		P value
    	DP			DP
    	15 Gy	≥20 Gy		15 Gy	≥20 Gy
    FFLF	88.8%	96.4%	0.42	53.4%	88.2%	0.08
    FFRN	100%	98%	--	98%	92%	0.43

    
    
    Conclusion:
    Our results suggest that, particularly for lesions >1 cm, DP ≥ 20 Gy correlates with improved FFLF, and similar FFRN rates, compared to DP 15 Gy.
    
    

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