2158 An analysis of anatomic landmark mobility and setup errors in radiotherapy for lung cancer

Proceedings

of the 39th Anrmal

ASTRO

319

Meeting

2157 PA’ITERNS NONSMALL

OF FAILURE AND OVERALL CELL LUNG CANCER

P.M. Gould, J.A. Bonner, T.E. Sawyer, Mayo Clinic, Rochester, MN 55905

SURVIVAL

C. Deschamps,

IN PATIENTS

WITH

COMPLETELY

R.L. Foote, V.F. Trastek, M.S. Allen,

RESECTED P.C. Pairolero,

T3NOMO C. Lange, H. Li

Previous studies of patients with surgically resected nonsmall cell lung cancer and chest wall invasion have Purpose/Objective: shown conflicting results with respect to prognosis. Whether high risk subsets of the T3NOMO Population exist with respect to local, regional, and distant control as well as overall survival has been difficult to ascertain due to small numbers of patients in most reported series. Therefore, a review of patients with completely resected T3NOMO nonsmall cell lung cancer was undertaken to analyze patient and rumor characteristics as well as surgical interventions that might influence patterns of failure and overall survival. review was performed for all patients (91) with T3NOMO nonsmall cell lung cancer who Materials and Methods: A retrospective had undergone a complete resection between the years 1979 to 1993. The following potential prognostic factors were recorded from each patients history: tumor size, tumor location (bronchus vs. pleura vs. chestwall), tumor grade, histology, patient age, the use of adjuvant radiation therapy (17/91 patients received adjuvant therapy), and the type of surgical procedure performed (chestwall resection vs. extrapleural resection). The actuarial rates of freedom from local recurrence (FFLR), freedom from regional nodal recurrence (FFRR), freedom from distant recurrence (FFDR), and overall survival were calculated from the date of diagnosis by the method of Kaplan-Meier. Results:

The following

2 Year 5 Year

*Only

3 local failures

table illustrates

two and five year outcomes:

a!!&

FFRR

94%

76%

74%

es 47%

94%*

73%

63%

32%

noted

None of the patients, rumor, or treatment parameters outlined in the above table.

characteristics

that were analyzed

were associated

with a significant

influence

on the four

Conclusion: Patients with completely resected T3NOMO nonsmall cell lung cancer have a similar local control and overall survival the tumor irrespective of primary location, type of surgery performed, or use of adjuvant radiation therapy. Additionally, recurrence rate and overall survival found in this study support the placement of this group of patients in the IIB stage of the proposed 1997 AJCC lung staging classification.

2158 AN ANALYSIS OF ANATOMIC LUNG CANCER

LANDMARK

MOBILITY

AND SETUP ERRORS IN RADIOTHERAPY

FOR

M.J. Samson, J.R. van Siimsen de Koste, J.C.J. de Boer, J.J. Tankink, M.B.J. Verstrsate, M. Eswrs, A.G. Visser and S. Senan Department of Radiation Oncology, University Netherlands.

Hospital Rotterdam-Daniel

den Hoed Cancer CenteriDijkzigt

PIWROSC: TO identify visible structures in the thorax which exhibit little internal setup deviations in lung cancer patients with the use of these structures.

motion

during

irradiation

Hospital, Rotterdam,

and, to detam&

random

The

and system&

Methods: Ten patients with lung cancer were set up in the supine position, and aligned using lasers. No immobilization devices were used. With an electronic portal imaging device (Siemens Beam VietiLLs), 12 sequential images (exposure 0.54 sec.; processing time 1.5 sec.) were obtained during a single fraction of radiotherapy. These “movie loops” were generated for the A-P fields during each of 3-5 fractions. In order to determine the mobility of internal structures during each fraction, visible structures such as the trachea, carina, the upper chest wall, aortic arch, clavicle and parsspinal line were contoured manually in each image and matched with the first image of the corresponding movie loop by means of a cross-correlation algorithm Translations in the cranial and lateral directions and in-plane rotations were determined for each structure separately. As the reference image represents a random position, relative movements were determined by comparing the translations and rotation for every image to the calculated means per movie-loop. Standard deviations of the relative movements were determined for each structure and each patient. Patient setup was evaluated for 15 patients with lung cancer. Setup was not corrected at any time during the treatment. The electronic portal images of each ftaction were matched with the digitized simulator films by using a combination of the structures which had been determined to be relatively stable in the i&a-fractional analysis. &&: In the i&a-fractional analysis 120 to 380 matches were made per structure (a total of 1400) The standard deviation (SD) oftranslations in the lateral direction was small (51 mm) for the trachea, thoracic wall, pamspinal tine and aortic arch. This was also the case for the SD of the translations in the cranial direction of the clavicle, aortic. arch and upper thoracic wsll The csrina wss found to be relatively mobile ( up to 6 mm) in both directions. The SD for in-plane rotations was negligible (CO.5 deg.) for all structures. The interpatient variation was very small (SD < 0.5 -I In a preliminary analysis of patient setup, the random errors for translations are 2.0 mm in the lateral direction and 2.4 nun in the cranial direction (1 SD). The standard deviations of systematic errors are about 3 mm in both diiections. In plane rotations were found to be negligible. ~onelusion~: We have identified a number of structures which exhibit little internal motion in the f?ontal plane, and recommend that a combination of these structures be used as anatomic landmarks for setup verification during radiotherapy of thoracic tumors. Preliminary results indicate that setup errors of patients with lung cancer in our center appear to be acceptable, even though no specific immobilization devices were used.