INTRODUCTION

The majority of clinical trials addressing outcomes in limited-stage small cell lung cancer (LS-SCLC) following definitive chemoradiotherapy have relied on 3D conformal radiotherapy (3DCRT) techniques.

Intensity modulated radiotherapy (IMRT) may decrease toxicity or facilitate dose escalation, but clinical data is lacking.

RESULTS

CONCLUSIONS

OBJECTIVE

In our dataset, patients with more advanced stage were more likely to be treated with IMRT than 3DCRT. Overall survival was significantly worse in the IMRT group, presumably due to higher disease stages represented in this group and unaccounted treatment

variables. However, local control was not significantly different between the 3DCRT and IMRT-treated patients. Despite larger treatment volumes, IMRT was associated with similar dosimetric parameters compared to 3DCRT, except for lower hotspots, higher lung volumes

receiving low doses of RT (i.e., lung V5 and V10), and lower heart V30. The rates of grade 2+ toxicity were comparable for IMRT vs. 3DCRT, except for worse fatigue in the IMRT group. This may be in part due to larger treatment

volumes in the IMRT group. Results from ongoing clinical trials may support dose escalation for LS-SCLC in the future. The enhanced conformality of IMRT may facilitate meeting dose

constraints in this setting, and based on our retrospective experience, use of this radiation delivery technique does not appear to result in compromised local tumor control in the thorax.

Intensity Modulated versus 3D Conformal Radiation Therapy for Limited Stage-Small Cell Lung Cancer

Carmen A. Pereza,1, Amanda McLanea,1, Andreas Rimnera,1, Daphna Y. Gelbluma,1, Richard M. Gewantera,1, Lee M. Krugb,1, Maria C. Pietanzab,1, Kenneth E. Rosenzweiga,2, Abraham J. Wua,1

Department of Radiation Oncologya, Thoracic Oncology Service/Department of Medicineb, Mount Sinai School of Medicine2, Memorial Sloan-Kettering Cancer Center New York, NY1

To compare disease control outcomes, dosimetric parameters, and toxicity following either 3DCRT- or IMRT-based definitive chemoradiotherapy for LS-SCLC.

METHODS

I. Outcomes at median follow-up of 20 months

p = 0.129

55%

36%

3DCRTN = 72

IMRTN = 77

Total N = 149

Deaths 46 (64%) 53 (69%) 99 (66%)

Distant Failures (DF) 33 (46%) 41 (53%) 74 (50%)

Locoregional Failures (LRF) 15 (21%) 20 (26%) 35 (23%)

Patient Characteristics Total 3DCRT IMRT p value (Pearson Chi-

square)MEDICAL HISTORY

Age (years) Median [range] 64 [43-93] 63 [45-84] 66 [43-93] 0.987

Gender Male 43% 44% 42% 0.722

Female 57% 56% 58%

Smoking History Positive 96% 97% 95% 0.453

Weight loss >10lb Yes 17% 20% 16% 0.527

KPS Median [range] 80 [60-100] 80 [60-100] 80 [60-100] 0.987

STAGING

PET Yes 93% 89% 97% 0.038

Brain MRI/CT Yes 97% 94% 100% 0.036

Stage Grouping (AJCC 7th Ed.) I A 2% 3% 0% <0.001

I B 2% 2% 3%

II A 11% 19% 6%

II B 9% 11% 7%

III A 54% 50% 57%

III B 22% 15% 27%

TREATMENT

Surgery Complete Resection 5% 7% 3% 0.210

No/Incomplete 95% 93% 97%

Chemotherapy Timing Concurrent 80% 82% 78% 0.541

Sequential 20% 18% 22%

4D-CT Simulation Yes 7% 7% 8% 1.000

RT fractionation: BID BID 53% 60% 47% 0.113

Planned dose (cGy) Median [range] 4500 [n/a] 4500 [n/a] 4500 [n/a] 1.000

RT treatment break Yes 14% 12% 17% 0.429

RT fractionation: Daily Daily 47% 40% 53% 0.113

Planned dose (cGy) Median [range] 5400 [4000-6600] 5400 [4000-5940] 5400 [4500-6600] 1.000

RT treatment break Yes 23% 24% 22% 0.128

PCI Yes 48% 54% 42% 0.124

Statistics: Kaplan-Meier methods to estimate survival outcomes; Log-rank test to assess univariate associations; Mann-Whitney U test (nonparametric test) to compare the distribution of dosimetric data

Retrospective Study Profile

149 LS-SCLC patients• Diagnosed 2003-2009• Treated at MSKCC with thoracic RT and platinum-based

chemotherapy

72 treated with 3DCRT• 70/72 (97%) completed intended RT dose• 26/72 (36%) with retrievable dosimetric data

77 treated with IMRT• 70/77 (91%) completed intended RT dose• 76/77 (99%) with retrievable dosimetric data

II. Dosimetric Parameters

Str

atifi

ed b

y S

tage

Parameter Mean Values (range) p value

3DCRT IMRT

Total PTV Volume (cc) 520 (120-1151) 677 (160-1849) 0.053

Relative Dmax 116% (107-138%) 110% (97-127%) <0.005

Lung V5 52% (24-76%) 59% (28-80%) 0.009

Lung V10 41% (21-60%) 45% (22-67%) 0.019

Lung V20 29% (14-44%) 30% (14-45%) 0.546

Lung V30 24% (7-37%) 22% (7-32%) 0.084

Lung Mean Dose (cGy) 1559 (907-2230) 1540 (767-2044) 0.628

Heart Mean Dose (cGy) 1637 (142-3911) 1443 (79-3727) 0.271

Heart V30 27% (0-68%) 17% (0-84%) 0.031

Esophagus Dmax (cGy) 5040 (4009-6352) 5295 (3917-7159) 0.094

Spinal Cord Dmax (cGy) 3744 (1632-5033) 3767 (379-4940) 0.779

III. Grade 2+ Toxicity

3DCRT IMRT

Pneumonitis

Esophagitis

Fatigue

% Incidence

8.8%

7%

34.1%

45.5%

17.1%

35.1%

p = 0.764

p = 0.235

p = 0.04

3DCRT

IMRT

vs.

Images courtesy of Margie Hunt

p = 0.030

63%, median 40m

45%, median 21m

p = 0.499 p = 0.062 p = 0.880

64%

80%

p = 0.118