Patient characteristics
Data were collected from 36 patients with lung cancer (median age, 68 years; range, 45–88 years) who received definitive re-irradiation using IMRT for local recurrence after (chemo-)radiotherapy in the locally advanced stage. The patient characteristics are summarized in Table 1. Among the included patients, 29 (80.6%) and 7 (19.4%) were male and female, respectively. Performance status (PS) according to Eastern Cooperative Oncology Group (ECOG) was 0–1 and 2–3 in 31 (86.1%) and 5 (5.6%) patients, respectively. Histology findings showed that 11 (30.6%), 14 (38.9%), and 11 (30.6%) patients had adenocarcinoma, squamous cell carcinoma, and small cell carcinoma, respectively. Among the analyzed patients, 22 (61.1%), 13 (36.1%), and 1 (2.8%) had primary site, lymph node, and both primary and lymph node recurrence, respectively, while 23 (63.9%) and 7 (19.4%) patients had recurrent tumors that came in contact with the trachea/bronchus and esophagus, respectively. The duration from initial radiotherapy to re-irradiation was 23.4 (range, 8.5–102.6) months. The median initial radiation dose, re-irradiation dose, and total dose (BED10) was 72 Gy (range, 48.0–84.0), 86.8 Gy (range, 56.0–119.6), and 154.3 Gy (range, 107.8–191.6), respectively, while the median follow-up was 14.6 months (range, 0.4–88.6).
Table 1
Characteristics
|
|
|
|
Age
|
Median (range)
|
68
|
(45–88)
|
Sex
|
Male
Female
|
29
7
|
(80.6%)
(19.4%)
|
PS
|
0,1
2–4
|
31
5
|
(86.1%)
(5.6%)
|
Histology
|
AC
SCC
SCLC
|
11
14
11
|
(30.6%)
(38.9%)
(30.6%)
|
Recurrent sites
|
Primary site
LNs
Both
|
22
13
1
|
(61.1%)
(36.1%)
(2.8%)
|
Organs adjacent to the recurrent tumor
|
Trachea/bronchus
Esophagus
|
23
7
|
(63.9%)
(19.4%)
|
DM
|
Positive
Negative
|
5
31
|
(13.9%)
(86.1%)
|
Treatment interval (months)
|
Median (range)
|
23.4
|
(8.5–102.6)
|
Dose of initial RT (BED10)
|
Median (range)
|
72.0
|
(48.0–84.0)
|
Dose of re-RT (BED10)
|
Median (range)
|
86.8
|
(56.0–119.6)
|
Cumulative dose (BED10)
|
Median (range)
|
154.3
|
(107.8–191.6)
|
PTV (cc)
|
Median (range)
|
73.6
|
(8.8–460.6)
|
Abbreviations: PS, performance status; AC, adenocarcinoma; SCC, squamous cell carcinoma; SCLC, small cell carcinoma; LN, lymph node; DM, distant metastases; BED, biological effective dose; PTV, planning target volume. |
Treatment
Computed tomography (CT) and magnetic resonance imaging for treatment planning were obtained in the supine position using a BrightSpeed™ CT scanner (GE Healthcare, Chicago, IL) and SIGNA EXCITE HDx 1.5T™ (GE Healthcare, Chicago, IL). Clinical target volume (CTV) was considered equal to gross tumor volume (GTV), while the planning target volume (PTV) was calculated by adding a margin of approximately 5 mm to each CTV. Plans were generated using BrainSCAN (ver. 5.31) RT Treatment Planning Software (Brainlab AG, Munich, Germany) with the pencil beam algorithm before November 2010 and thereafter using iPlan RT Dose (ver. 4.1.2) software (Brainlab AG) with the Monte Carlo algorithm. All patients underwent IMRT using a 6-MV linear accelerator (Novalis, Brainlab AG). Daily image guidance was performed, while treatments were performed on consecutive days.
Clinical outcome evaluation
In principle, patients were followed-up after 4 weeks and then every 3 months thereafter, with CT being performed at each visit. The latest visit or date of contact was used for right-censoring patients who were alive at the time of analysis. Tumor responses after re-irradiation were evaluated using Response Evaluation Criteria in Solid Tumors ver1.1.10 Local control (LC) was defined as recurrence at the re-irradiated site. Progression-free survival (PFS) was as the duration from re-irradiation to disease progression or death from any cause. Overall survival (OS) was defined as the duration from re-irradiation to death from any cause. Late toxicities ≥ grade3 were evaluated according to the Common Terminology Criteria for Adverse Events ver. 3.0.
Statistical analysis
Data analysis was performed using JMP pro 14 (SAS Institute Inc., Cary, NC). LC, PFS, and OS rates were calculated using the Kaplan–Meier method. Prognostic factors were identified through univariate analysis using the log-rank test and multivariate analysis using the COX proportional hazards model. Statistical tests were based on a two-sided significance level, with p values of < 0.05 indicating statistical significance.