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Y.C. Ahn
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MINI 33 - Radiotherapy and Complications (ID 164)
- Event: WCLC 2015
- Type: Mini Oral
- Track: Treatment of Locoregional Disease – NSCLC
- Presentations: 1
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MINI33.09 - Impact of Tumor Regression and Need for Re-Plan during Radiation Therapy for Stage IIIB Lung Cancer: Dosimetric Comparison between IMRT and IMPT (ID 3063)
18:30 - 20:00 | Author(s): Y.C. Ahn
- Abstract
- Presentation
Background:
Radiation pneumonitis (RP) is the most worrying complication following high dose radiation therapy (RT) for loco-regionally advanced lung cancer. Intensity modulated radiation therapy (IMRT) and intensity modulated proton therapy (IMPT) are expected to reduce RP compared with conventional RT technique. Adaptive re-plan is usually indicated to accommodate tumor shrinkage and position changes during fractionated RT course. This study is to comparatively evaluate dosimetric differences between RT techniques and interval changes of these parameters assuming that initial IMRT and IMPT plans are continued throughout RT course without adaptive re-plan.
Methods:
Ten patients who were given concurrent chemo-radiotherapy by IMRT (66 Gy/33 fractions, weekly Docetaxel/CDDP #6) for having N3(+) stage IIIB lung cancer were selected. Surrogate rival IMPT plan on each patient was generated to compare with initial IMRT plan. Beam numbers used in IMRT and IMPT were 6-7 and 3. Second CT obtained during 3[rd]-4[th] week for adaptive IMRT plan was used to generate second sets of IMRT and IMPT plans, assuming that adaptive plan had not been done. Differences between initial RT techniques and changes in dosimetric parameters including conformity index (CI), homogeneity index (HI) and dose-volume histogram (DVH) of target and normal organs, which could have occurred by 2 RT techniques, were compared.
Results:
When comparing initial IMRT and IMPT plans, IMPT showed advantageous features over IMRT with respects to median HI (1.08 vs. 1.02), mean doses (D~mean~) to lung, esophagus, and heart, lung volumes receiving 5 Gy (V~5~), 10 Gy (V~10~), 20 Gy (V~20~), 30 Gy (V~30~), and 40 Gy (V~40~) and maximum dose (D~max~) to spinal cord (all p<0.05), respectively. Mean gross tumor volumes (GTV) on initial and second CT’s were 90.9 (48.1~163.7) cm[3] and 52.2 (23.1~89.7) cm[3] and median GTV reduction was 42.2% (51.3%-84.4%). More dosimetric parameters could have changed significantly by IMPT (CI, HI, V~5~, V~10~, V~20~, V~30~, D~mean~ to lung and heart, and D~max~ to spinal cord) than IMRT (CI, HI, V~20~, D~max~ to spinal cord and heart), respectively. Absolute increase in D~max~ to spinal cord was estimated as 0.53 Gy by IMRT and 4.79 Gy by IMPT (p=0.003).
Conclusion:
Impact of GTV regression during RT course and need for adaptive re-plan seem evident. More uncertainties on dosimetric parameters and higher doses to spinal cord are expected by IMPT than by IMRT if re-plan is not applied. Optimal timing and frequency of adaptive plans, however, need to be further evaluated.
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P2.02 - Poster Session/ Treatment of Localized Disease – NSCLC (ID 210)
- Event: WCLC 2015
- Type: Poster
- Track: Treatment of Localized Disease - NSCLC
- Presentations: 1
- Moderators:
- Coordinates: 9/08/2015, 09:30 - 17:00, Exhibit Hall (Hall B+C)
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P2.02-036 - Radiation Therapy Alone in cT1-3N0 Lung Cancer Patients Who Are Unfit for Surgery or Stereotactic Ablative Radiation Therapy (ID 3144)
09:30 - 17:00 | Author(s): Y.C. Ahn
- Abstract
Background:
High dose radiation therapy (RT) alone is recommended to cT1-3N0 lung cancer patients, who are unfit for surgical resection or stereotactic RT based on medical comorbidity, tumor size and location. This study is to evaluate clinical outcomes and costs following definitive RT alone using 2 modest hypo-fractionated dose schemes.
Methods:
Retrospective review on 116 patients who received high dose RT alone from January 2001 till December 2013 was done. Median age was 74 years and 91 patients (78.4%) were male. All had cT1-3N0 disease and 65 patients (56.0%) had squamous cell carcinoma, followed by adenocarcinoma in 35 (30.2%). Dose-fractionation scheme of 60 Gy in 20 fractions over 4 weeks was applied to 79 patients from 2001 till 2010 (68.1%, Group I). Meanwhile, 2 dose-fractionation schemes were used from 2011 till 2013: 60 Gy in 20 fractions to 17 patients (14.7%, Group II); and more hypo-fractionated scheme of 60 Gy in 15 fractions over 3 weeks to 20 patients (17.2%, Group III). 60 Gy in 15 fractions was chosen on individual basis if RT-related acute side effects (bronchitis, esophagitis) could be avoided based on tumor location and geometry. Group I/II patients had central tumors (defined as within 2 cm from lobar bronchi) more frequently (78.5% vs. 64.7% vs. 35.0%, p<0.0001), and larger mean tumor size (4.2 cm vs. 5.0 cm vs. 3.8 cm, p=0.0725) than Group III. Elective nodal irradiation to regional lymphatics (median 30 Gy/10 fractions) was delivered to 30 patients: 23 in Group I (29.1%); seven in Group II (41.2%); and none in Group III (0%), respectively (p=0.0341). Local control (LC), progression free survival (PFS), overall survival (OS), and RT-related toxicity profile were estimated and compared.
Results:
After median 19.3 (1.2-119.5) months’ follow-up, 68 patients (58.6%) experienced disease progression, and 66 (56.9%) died. 2-year LC and PFS rates of all patients were 62.0% and 39.3%, respectively, which were not different between Groups (59.3% and 36.1% vs. 52.1% and 26.9% vs. 78.8% and 61.6%, p=0.3010 and 0.1620, respectively). 2-year OS rate of all patients was 57.5%, and was significantly better in Group III (51.3% vs. 69.1% vs. 83.0%, p=0.0232). Grade ≥2 pneumonitis developed in 27 patients (23.3%), and was not different between Groups (19.0% vs. 35.3% vs. 30.0%, p=0.1908), while Grade ≥2 esophagitis developed in 22 patients (19.0%), however, none in Group III (22.8% vs. 23.5% vs. 0%, p=0.0373). Good performance status (ECOG 0-1 vs. 2-3) and low cT-stage (T1-2 vs. T3) were significantly favorable factors affecting LC, PFS, and OS, however, central location of tumor was not. Costs incurred by RT under Korean Health Insurance Policy were 6,080,000 KW in Groups I and II and 4,707,500 KW in Group III, respectively.
Conclusion:
Hypo-fractionated RT delivering 60 Gy in either 15 or 20 fractions could lead to reasonably favorable and comparable clinical outcomes in cT1-3N0 lung cancer. 60 Gy in 15 fractions in selective cases as in Group III, however, seems more cost-effective and attractive by virtue of shorter RT duration, lower cost, and increased patients’ convenience.
