Consequences of anatomic changes and respiratory motion on radiation dose distributions in conformal radiotherapy for locally advanced non-small-cell lung cancer.

PURPOSE: To determine the effect of interfractional changes in anatomy on the target and normal tissue dose distributions during course of radiotherapy in non-small-cell lung cancer patients. METHODS AND MATERIALS: Weekly respiration-correlated four-dimensional computed tomography scans were acquired for 10 patients. Original beam arrangements from conventional and inverse treatment plans were transferred into each of the weekly four-dimensional computed tomography data sets, and the dose distributions were recalculated. Dosimetric changes to the target volumes and relevant normal structures relative to the baseline treatment plans were analyzed by dose-volume histograms. RESULTS: The overall difference in the mean +/- standard deviation of the doses to 95% of the planning target volume and internal target volume between the initial and weekly treatment plans was -11.9% +/- 12.1% and -2.5% +/- 3.9%, respectively. The mean +/- standard deviation change in the internal target volume receiving 95% of the prescribed dose was -2.3% +/- 4.1%. The overall differences in the mean +/- standard deviation between the initial and weekly treatment plans was 3.1% +/- 6.8% for the total lung volume exceeding 20 Gy, 2.2% +/- 4.8% for mean total lung dose, and 34.3% +/- 43.0% for the spinal cord maximal dose. CONCLUSION: Serial four-dimensional computed tomography scans provided useful anatomic information and dosimetric changes during radiotherapy. Although the observed dosimetric variations were small, on average, the interfractional changes in tumor volume, mobility, and patient setup was sometimes associated with dramatic dosimetric consequences. Therefore, for locally advanced lung cancer patients, efforts to include image-guided treatment and to perform repeated imaging during the treatment course are recommended.

A phase II study on stereotactic body radiotherapy for stage I non-small cell lung cancer.

BACKGROUND AND PURPOSE: The outcome of stage I non-small cell lung cancer (NSCLC) patients treated with conventional radiotherapy is inferior to that of patients treated surgically. We aimed to evaluate the clinical outcome of stereotactic body radiotherapy (SBRT) in the treatment of stage I NSCLC. MATERIALS AND METHODS: We performed SBRT for 31 stage I NSCLC patients. Of these, 20 were medically inoperable, and 11 refused surgery. Nineteen tumours were T1-stage masses, and 12 tumours were T2. Median tumour size was 25 mm. SBRT was administered as 45 Gy/3 fractions; however, when the tumour was close to an organ at risk, 60 Gy/8 fractions were used. These doses were prescribed at the centre of the tumours. RESULTS: The median duration of observation for all patients was 32 months (range, 4-87 months). In 9 of the 31 cases, local recurrence was observed. The 3-year local control rates of T1 and T2 tumours were 77.9% and 40.0%, respectively. The 3-year overall and cause-specific survival rates were 71.7% and 83.5%, respectively. Although the symptoms improved with medical treatment, 5 patients developed acute pulmonary toxicity > or =grade 2. CONCLUSIONS: SBRT is safe and effective for stage I NSCLC patients. However, a more intensive treatment regimen should be considered for T2 tumours.

Assessment of gross tumor volume regression and motion changes during radiotherapy for non-small-cell lung cancer as measured by four-dimensional computed tomography.

PURPOSE: To investigate the magnitudes of the changes in mobility and volume of locally advanced non-small-cell lung cancer (NSCLC) tumors during radiotherapy, using four-dimensional computed tomography (4DCT). METHODS AND MATERIALS: Five to ten 4DCT data sets were acquired weekly for each of 8 patients throughout treatment. Gross tumor volumes (GTVs) were outlined on each data set. Volumes and coordinates of the GTV centroids were calculated at the 0 (end-inspiration) and 50% (end-expiration) respiration phases. Trends in magnitudes of intrafraction and interfraction positional variations were assessed for the GTV and internal target volume (ITV) during treatment. RESULTS: Tumor volume reduction ranged from 20% to 71% (end-inspiration) and from 15% to 70% (end-expiration). Increased tumor mobility was observed in the superior-inferior and anterior-posterior directions. However, no trends in tumor motion were observed. Motion along the superior-inferior direction was significantly greater (p < 0.001), with mean +/- SD values of 0.86 +/- 0.19 cm, as compared with 0.39 +/- 0.08 cm and 0.19 +/- 0.05 cm in the anterior-posterior and right-left directions, respectively. A marginally significant (p = 0.049) increase in total GTV positional variation was observed with increasing treatment weeks, and similar results were seen for the interfractional ITV mobility. CONCLUSIONS: Because of changes in tumor size and mobility, an explicit initial determination of the ITV may not be sufficient, especially where small setup margins are used. Repeat 4DCT scans might be warranted for highly mobile tumors to reduce the potential for missing the tumor.

Evaluation of inter- and intrafraction organ motion during intensity modulated radiation therapy (IMRT) for localized prostate cancer measured by a newly developed on-board image-guided system.

PURPOSE: To investigate prostatic organ motion at both setup and intrafraction using an onboard image-guided system. An intrafraction field-based repositioning method also was evaluated. MATERIALS AND METHODS: A dual fluoroscopy with amorphous-silicon flat panel (DFFP) system was used for the three-dimensional registration of implanted markers in the prostate of eight organ-confined cancer patients planned for treatment with intensity modulated radiation therapy (IMRT). Day-to-day motion errors were quantified and intrafraction displacements of more than +/-1 mm were corrected. RESULTS: Among 214 fractions and 565 system views, day-to-day mean magnitude of marker discrepancy +/- standard deviation (SD) was 1.76 +/- 1.4 mm, 3.14 +/- 1.6 mm, and 3.78 +/- 2.4 mm in the right-left, cranial-caudal, and anterior-posterior directions, respectively. The intrafractional mean magnitude +/- SD of marker displacement was 0.45 +/- 0.7 mm, 1.08 +/- 1.38 mm and 1.45 +/- 1.70 mm in the right-left, cranial-caudal, and anterior-posterior directions, respectively. Intrafraction corrected sessions (84/214) showed a median (range) of motion of 0.1 mm (-1.2 to 0.7 mm), -0.2 mm (-2.1 to 1.1 mm), and -0.2 mm (-1.7 to 2.0 mm) in the right-left, cranial-caudal, and anterior-posterior directions, respectively. CONCLUSION: Motion uncertainty can be considerably decreased with daily use of the DFFP system. Reduced intrafraction organ motion clearly endorsed the value of the repositioning approach, allowing a safer dose escalation protocol.

Radiation therapy combined with cis-diammine-glycolatoplatinum (Nedaplatin) and 5-fluorouracil for untreated and recurrent esophageal cancer.

From January 1999 to November 2000, a total of 24 esophageal cancer patients (17 untreated and 7 recurrent cases) were treated with radiation therapy (60-70 Gy) combined with cis-diammine-glycolatoplatinum (Nedaplatin) (80-120 mg/body) and 5-fluorouracil (5-FU) (500-1,000 mg/body/24 h, continuous infusion for 5 days). Grade III leukocytopenia was observed in 6 (25%) of the patients. Grade III and IV thrombocytopenia was observed in one patient each. The 1-year and 2-year survival rates for definitively irradiated patients were 59% and 39%, respectively, and for patients with postoperative recurrence 69% and 69%, respectively. High-dose radiation combined with Nedaplatin and 5-FU is a safe and effective method for treating esophageal cancer.