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Volume 99 � Number 2S � Supplement 2017 Poster Viewing E487

Author Disclosure: A. Nikolaev: None. R.K. Benda: None. C.Y. Shang:

None. M.E. Kasper: None. T.R. Williams: None.

3153

Effect of Tumor Volume Doubling Time on Prognosis for Stage I Nonesmall Cell Lung Cancers

H. No,1 H.M. Gagne,2 C.J. Nelson,2 M. Kinsey,3 G. Garrison,3 J. Kikut,4

G. Gentchos,5 D. Seward,6 N. Sidiropoulos,6 E. Folefac,7 B. Leavitt,8

T. Ashikaga,9 K. Dragnev,10 S.H. Lin,11 and C.J. Anker2; 1The University

of Vermont Robert Larner MD College of Medicine, Burlington, VT, 2Division of Radiation Oncology, University of Vermont Cancer Center,

Burlington, VT, 3Division of Pulmonary and Critical Care Medicine,

University of Vermont Medical Center, Burlington, VT, 4Nuclear Medicine

and Diagnostic Radiology, University of Vermont Medical Center,

Burlington, VT, 5Department of Radiology, University of Vermont Medical

Center, Burlington, VT, 6Department of Pathology and Laboratory

Medicine, University of Vermont Medical Center, Burlington, VT, 7Department of Hematology and Oncology, University of Vermont Cancer

Center, Burlington, VT, 8Division of Cardiothoracic Surgery, University of

Vermont Medical Center, Burlington, VT, 9College of Engineering and

Mathematical Sciences, University of Vermont, Burlington, VT, 10Norris

Cotton Cancer Center, Dartmouth-Hitchcock Medical Center, Lebanon,

NH, 11Department of Radiation Oncology, The University of Texas MD

Anderson Cancer Center, Houston, TX

Purpose/Objective(s): Computed tomography (CT)-based screening has been found to improve overall survival (OS) by detecting earlier stage

non-small cell lung cancers (NSCLC); however, some tumors may

exhibit indolent growth and additional prognostic indicators are needed

for treatment management decisions. The literature suggests that lung

cancers with volume doubling times (VDTs) �400 days might be over- diagnosed. We hypothesized better outcomes would be associated with

longer VDTs.

Materials/Methods: A retrospective review identified 172 consecutive patients from XXXX with Stage I NSCLC diagnosed between January

2010 - December 2012, of whom 37 met the following additional criteria

for this study: �1 year follow-up and �3 month interval between �2 CT scans prior to treatment. Collected data included patient demographics,

stage, operability status, histology, Karnofsky Performance Score, Charl-

son-Deyo Comorbidity Index (CDCI) grades, smoking status, and tumor

size changes. VDTs were calculated using a modified Schwartz equation

for exponential growth from CT-derived tumor measurements. Estimates

of recurrence-free survival (RFS) and OS were calculated from the date of

biopsy using the KaplaneMeier method. Univariate Cox proportional

hazards models for RFS and OS were evaluated, with significance defined

as p<0.05.

Results: Median follow-up for all patients was 60.4 months, and the median time between analyzed scans was 10.2 months. The median age

was 71 years (range, 46 - 86), with a median KPS of 70 and all patients

having a CDCI �1. Fifty-nine percent (nZ22) of the patients were female and 54% (nZ20) exhibited VDTs �400 days. Seventy eight percent (nZ29) were diagnosed with adenocarcinoma, 14% squamous cell, and 8% were not specified. Regarding treatment, 59% (nZ22) underwent surgery, 24% received radiation, 11% received radiofrequency ablation,

and 5% were observed. Improved RFS was significantly associated with a

VDT �400 days (pZ0.003), with a 5-year RFS of 100% vs. 57%. Four- teen percent (nZ5) recurred locally and 1 patient had distant failure, all with VDTs <400 days. No other investigated factor was significantly

associated with either OS or RFS, but 5-year OS was 74% vs. 62%

(pZ0.34) for patients with VDTs �400 and <400, respectively. Conclusion: Longer VDT (‡400 days) was associated with significantly improved RFS. Results suggest patients with longer VDTs have a better

prognosis and perhaps less aggressive management may be taken, such as

an active surveillance approach. Prospective studies with an emphasis on

cause-specific survival are warranted to investigate whether it is safe to

delay or avoid biopsy and treatment of indolent lesions.

Author Disclosure: H. No: Research Grant; Northern New England Clin-

ical Oncology Society. H.M. Gagne: None. C.J. Nelson: Travel Expenses;

Elekta. M. Kinsey: None. G. Garrison: Research Grant; Northern New

England Clinical Oncology Society. J. Kikut: Research Grant; Northern

New England Clinical Oncology Society. G. Gentchos: None. D. Seward:

None. N. Sidiropoulos: Research Grant; Northern New England Clinical

Oncology Society. E. Folefac: None. B. Leavitt: Research Grant; Northern

New England Clinical Oncology Society. T. Ashikaga: None. K. Drag-

nev: Consultant; Borhringer Ingelheim. S.H. Lin: Research Grant; Elekta,

Inc, Hitachi Chemical, Inc, Peregrine Pharmaceuticals, Inc, Roche/Gen-

entech, STCube Pharmaceuticals, Inc. C.J. Anker: Research Grant;

Northern New England Clinical Oncology Society.

3154

Local Tumor Control After Stereotactic Body Radiation Therapy for Early Lung Cancer is Not Impacted by the Use of Intensity Modulated Radiation Therapy or Respiratory Gating

T. Nsouli, J. Frandina, S. Tanny, R. Chaudhari, P. Rosenbaum, M.D. Mix,

J.A. Bogart, and P.D. Aridgides; SUNY Upstate Medical University,

Syracuse, NY

Purpose/Objective(s): Though stereotactic body radiation therapy (SBRT) has become a standard treatment option for stage I NSCLC, the

majority of published results relate to three-dimensional treatment plan-

ning (3D-CRT). Less data is available following treatment with IMRT, and

there is also limited published experience using respiratory gating, where

treatment is only delivered to a portion of the breathing cycle, during

SBRT.

Materials/Methods: Retrospective review of patients treated with SBRT for Stage I NSCLC between 2007 and 2015. All patients had a 4D

simulation with the Varian RPMTM system and abdominal compression

was used in the majority (81%). Respiratory gating was typically used

if longitudinal tumor motion exceeded 1cm. Patient characteristics,

treatment planning and delivery parameters, dosimetry information,

and patient outcomes were collected and analyzed using SPSS statis-

tical software (descriptive stats, bivariate procedures and survival

analyses).

Results: A total of 297 patients (median age 71, range 43-89) with stage I NSCLC were included. Pathology was confirmed in 94.6% of patients.

The majority of lesions were located in the upper lobes (60.9%) and

clinical stage T1A (68%). The use of 3DCRT and IMRT planning was

similar, 52% vs 48%, although an increased frequency of IMRT was

noted in more recent years. Respiratory gating was employed in

approximately 16% of cases (nZ51). The gating cohort included 78% lower lobe tumors, while 26% of lesions treated without gating were in

the lower lobes. The most common SBRT regimens were 48Gy in 4

fractions and 54-60Gy in 3 fractions. With a median follow up of 22.7

months, there were 17 local failures for a crude relapse rate of 5.7%.

Local tumor relapse was similar in patients treated with 3DCRT and

IMRT (6.5% vs 4.9%, pZ0.962), and relapse likewise was similar with and without respiratory gating (7.8% vs 4.9%, pZ0.560). In addition, T- stage, tumor size, pathology and SBRT regimen did not correlate with

local tumor control. Overall survival for the entire population approxi-

mated 72% at 2 years. Treatment appeared tolerated well with 6 docu-

mented grade 3+ events, and thus there were too few events to compare

toxicity amongst treatment cohorts.

Conclusion: The utilization of respiratory gating or the use of IMRT does not appear to compromise the therapeutic ratio for patients treated with

SBRT for stage I NSCLC.

Author Disclosure: T. Nsouli: None. J. Frandina: None. S. Tanny: None.

R. Chaudhari: None. P. Rosenbaum: None. M.D. Mix: None. J.A. Bo-

gart: Partner; Upstate University Radiation Oncology. Travel Expenses;

Alliance Clinical Trials. Chair, radiation oncology committee; Alliance.

P.D. Aridgides: None.