The deep inspiration breath-hold technique in the treatment of inoperable non-small-cell lung cancer

Validation of active breathing control in patients with non–small-cell lung cancer to be treated with CHARTWEL

PURPOSE

Active breathing control (ABC) was validated using patients with non-small-cell lung cancer (NSCLC) to be treated with continuous hyperfractionated accelerated radiotherapy weekend-less (CHARTWEL). Effects of breath hold (BH) on accuracy and normal tissue doses were evaluated.

METHODS AND MATERIALS

Eleven patients were studied. Immediately after a free breathing (FB) planning scan, two ABC scans (ABC 1 and 2) were performed to assess intrafraction variation. A third ABC scan (ABC 3) was performed some weeks later to assess interfraction variation. Assisted BH was set at 75% of vital capacity and reproducibility assessed using computed tomography (CT) lung volumes. Planning target volumes (PTVs), doses to lung and spinal cord for FB and ABC 1 scans were compared.

RESULTS

Results were available for 10 patients. Disease and elective nodal regions were easier to define on ABC scans making PTVs smaller. ABC lung volumes showed no significant variation over several weeks, percentage volume of whole lung receiving > or =20 Gy (V(20)) was reduced in all (median 6.4%, p = 0.005), and spinal cord dose in 80% (median 1.03 Gy, p = 0.02), of the plans.

CONCLUSION

ABC allowed reproducible BH, and enabled better delineation of tumor and normal structures, as well as reduction in PTV, V(20), and spinal cord dose.

Three-dimensional conformal radiotherapy in the radical treatment of non-small cell lung cancer

Patients with locally advanced, inoperable, non-small cell lung cancer (NSCLC) have a poor prognosis mainly due to failure of local control after treatment with radical radiotherapy. This overview addresses the role of three-dimensional conformal radiotherapy (3D CRT) in trying to improve survival and reduce toxicity for patients with NSCLC. Current techniques of 3D CRT are analysed and discussed. They include imaging, target volume definition, optimisation of the delivery of radiotherapy through improvement of set-up inaccuracy and reduction of organ motion, dosimetry and implementation and verification issues; the overview concludes with the clinical results of 3D CRT.

The Effect of Deep Inspiration Breath-hold on Tumour Oxygenation

AIM

To investigate the influence of deep inspiration breath-hold on the oxygen tension of in-vivo tumours measured using an Eppendorf pO2 histograph.

MATERIALS AND METHODS

Patients with accessible primary or metastatic tumours > or = 2 cm diameter were entered into a protocol measuring tumour oxygenation with an Eppendorf pO2 histograph during normal breathing (NB) and deep inspiration breath-hold (DIBH). Change in oxygen tension was assessed using the Wilcoxon Signed Ranks test.

RESULTS

Thirty patients were entered in to this protocol. The median maximum tumour dimension was 4 cm. The median of the median pO2 of these tumours was 18 mmHg. Tumours were assessed during NB and DIBH. Oxygen tension measurements along 1-3 pairs of tracks per tumour (median of 2) were obtained. The median number of measurements per track was 30 for NB and 29 for DIBH (range 17-59). In six tumours, the values during NB were significantly higher than during DIBH, whereas, for six other tumours, the relationship was the opposite; for the remaining 18 patients, no significant difference was observed.

CONCLUSION

These data show heterogeneity of tumour oxygenation seen with in-situ tumours both at baseline and as a result of DIBH. No systematic change in the Eppendorf pO2 measurements was seen as a result of DIBH; however, the individual tumour responses to DIBH varied dramatically.

New radiotherapy technologies

Conventional radiation therapy has had limited success in curing inoperable lung cancer due to poor local control. There is evidence to suggest that higher doses of radiation will improve local control. In order to safely deliver higher doses of thoracic radiation, advanced treatment techniques are required. Different biologic indices have been utilized to determine whether dose escalation can be safely accomplished, and the results have been reported from many institutions. Tumor motion control aids in treatment since it allows radiation oncologists to more accurately target tumors and therefore to spare more normal tissue from the radiation field. The imaging information from 18-FDG-PET scans also improves target delineation. Advanced treatment delivery techniques, such as three-dimensional conformal radiation therapy, intensity modulated radiation therapy, and stereotactic radiosurgery are also being used to safely escalate the radiation dose. This article explores the current literature on these issues and other advanced radiation therapy techniques.

Dose correlation for thoracic motion in radiation therapy of breast cancer

This work investigates the dose correlation for deformed objects due to thoracic motion for radiotherapy treatment of breast cancer. An analytical model has been developed to reconstruct patient anatomy based on the assumption that the body will expand or compress proportionally during respiration. The patient geometry at any phase during a breathing pattern is reconstructed using the CT data taken at the inspiration and expiration phases and the breathing level which can be related to the measured chest wall motion. A correlation between the voxels in the inspiration (or expiration) geometry and the voxels in the reconstructed geometry at any phase of the breathing pattern is established so that the dose can be accumulated during a treatment. The method has been implemented for treatment planning dose calculation by interfacing with a Monte Carlo code. The patient geometry files for different phases of the breathing pattern are generated and the three-dimensional dose data are obtained from the Monte Carlo simulations. The final dose distribution is reconstructed from the dose data at different breathing phases based on patient's breathing pattern associated with chest wall movements.

Initial clinical experience with moderate deep-inspiration breath hold using an active breathing control device in the treatment of patients with left-sided breast cancer using external beam radiation therapy

INTRODUCTION

We present our initial clinical experience using moderate deep-inspiration breath hold (mDIBH) with an active breathing control (ABC) device to reduce heart dose in the treatment of patients with early-stage, left-sided breast cancer using external beam radiation therapy (EBRT) limited to the whole breast.

METHODS AND MATERIALS

Between February and August 2002, 5 patients with Stages I/II left-sided breast cancer received EBRT limited to the whole breast using an ABC device. After standard virtual simulation, patients with >2% of the heart receiving >30 Gy in free breathing were selected. All patients underwent a training session with the ABC apparatus to determine their ability to comfortably maintain mDIBH at 75% of the maximum inspiration capacity. Three patients received 45 Gy to the whole breast in 25 fractions, and 2 patients received 50.4 Gy in 28 fractions. For each of the medial and lateral tangential beams, radiation was delivered during 2 or 3 breath hold durations that ranged from 18 to 26 s. "Step-and-shoot" intensity modulation was employed to achieve uniform dose distribution. Open beam segments were purposely delivered over 2 breath hold sessions and captured on electronic portal images to allow intra- and interfraction setup error analysis. All electronic portal images of the tangential beams were analyzed off-line using an in-house treatment verification tool to assess the anteroposterior, craniocaudal, and rotational uncertainties. Corrections were applied if necessary.

RESULTS

A comparison of treatment plans performed on breath-hold and free-breathing CTs showed that ABC treatments achieved a mean absolute reduction of 3.6% in heart volume receiving 30 Gy (heart V(30)) and 1.5% in the heart normal tissue complication probability. A total of 134 ABC treatment sessions were performed in the 5 patients. The average number of breath holds required per beam direction was 2.5 (4-6 per treatment) with a median duration of 22 s per breath hold (range: 10-26 s). Patients tolerated mDIBH well. The median treatment time was 18.2 min (range: 13-32 min), which was progressively shortened with increasing experience. A total of 509 portal images were analyzed. Combining measurements for all patients, the interfraction setup errors (1 SD) in the lateral and craniocaudal directions and in rotation were 2.4 mm, 3.2 mm, and 1 degrees, respectively, for the medial beam and 2.3 mm, 3.1 mm, and 1 degrees, respectively, for the lateral beam. For all patients, the intrafraction setup errors were about 1 mm and always less than 2 mm (1 SD).

CONCLUSION

Reduction in heart V(30) can be achieved in patients with left-sided breast cancer using mDIBH assisted with an ABC device. With increasing experience, ABC treatments were streamlined and could be performed within a 15-min treatment slot. Our results suggest that mDIBH using an ABC device may provide one of the most promising methods of improving the efficacy of EBRT in patients with left-sided breast cancer, particularly when wide tangential beams are employed. Breast cancer; Breath hold; Radiation therapy; Intensity modulated radiation therapy

Respiration-induced movement of the upper abdominal organs: a pitfall for the three-dimensional conformal radiation treatment of pancreatic cancer

Respiration-induced movement of the upper abdominal organs (pancreas, liver and kidneys) was assessed in 12 subjects using dynamic magnetic resonance imaging. The movement of each organ in the cranio-caudal, the lateral and the anterior-posterior direction was deduced from the movement of the center of gravity on two-dimensional images. This center of gravity was computed from the volume delineated on sequential 8-mm slices of both sagittal and coronal dynamic series. The largest movements were noticed in the cranio-caudal direction for pancreas and liver (23.7+/-15.9 mm and 24.4+/-16.4 mm). The kidneys showed smaller movements in the cranio-caudal direction (left kidney 16.9+/-6.7 mm and right kidney 16.1+/-7.9 mm). The movements of the different organs in the anterior-posterior and lateral directions were less pronounced. It is of the greatest importance to be aware of these movements in the planning of a conformal radiation treatment for pancreatic cancer.

Image-guided conformal radiation therapy planning and delivery for non-small-cell lung cancer

BACKGROUND

Our understanding of both the importance of local control for survival of patients with unresectable lung cancer and the inadequacy of conventional radiation therapy (RT) to provide this local control has undergone marked changes in the past 2 decades.

METHODS

A review was conducted of recent studies and meta-analyses in the literature that have convincingly demonstrated the value of thoracic irradiation in increasing long-term survival in patients with both small-cell lung cancer and non-small-cell lung cancer (NSCLC).

RESULTS

Large cooperative trials have shown long-term local control of only approximately 10% for NSCLC using conventionally planned radiation to doses of 60-64 Gy either as a single modality or when preceded by induction chemotherapy. Concurrent chemotherapy may modestly improve local control at the cost of greater acute esophageal toxicity. Simple escalation of radiation dose is limited by the tolerance of normal intrathoracic organs. Recent developments in anatomic and functional imaging, computerized RT planning, and RT delivery, as well as a reassessment of the appropriate target volumes for RT in the context of combined modality therapy, provide the capability to better conform regions of high dose to the target volume and test the hypothesis that increases in tumor dose will improve local control and survival.

CONCLUSIONS

Encouraging phase II data have been reported from single institutions using individually developed software and hardware. The availability of commercial tools for planning and delivering such conformal treatment will allow prospective assessment of the true value of these technologies in the management of patients with lung cancer.

Estimating volumetric motion in human thorax with parametric matching constraints

In radiotherapy (RT), organ motion caused by breathing prevents accurate patient positioning, radiation dose, and target volume determination. Most of the motion-compensated trial techniques require collaboration of the patient and expensive equipment. Estimating the motion between two computed tomography (CT) three-dimensional scans at the extremes of the breathing cycle and including this information in the RT planning has been shyly considered, mainly because that is a tedious manual task. This paper proposes a method to compute in a fully automatic fashion the spatial correspondence between those sets of volumetric CT data. Given the large ambiguity present in this problem, the method aims to reduce gradually this uncertainty through two main phases: a similarity-parametrization data analysis and a projection-regularization phase. Results on a real study show a high accuracy in establishing the spatial correspondence between both sets. Embedding this method in RT planning tools is foreseen, after making some suggested improvements and proving the validity of the two-scan approach.

CT evaluation of patient deep inspiration self-breath-holding: how precisely can patients reproduce the tumor position in the absence of respiratory monitoring devices?

The aim of the present study was to evaluate the reproducibility of tumor position under patient deep inspiration self-breath-holding in the absence of respiratory monitoring devices, as well as to compare the reproducibility of deep inspiration self-breath-holding on the verbal command of a radiation technologist (Passive mode) with that initiated by patients' own estimation (Active mode). Twenty patients with lung cancer were shown how the tumor and diaphragm move during the respiration cycle. Patients were instructed to hold their breath during deep inspiration and reproduce identical tumor position as well as possible either by the Active mode or by the Passive mode. After patients had practiced self-breath-holding during deep inspiration, a set of three CT scans was obtained for each of the two modes of self-breath-holding (6 CT scans total) to obtain randomly timed images of 2 mm thickness in the vicinity of the tumor. The first three scans were performed during breath-hold using the Active mode, and next three scans were using the Passive mode. Maximum difference in tumor position for the three CT scans was then calculated along three axes: cranial-caudal (C-C); anterior-posterior (A-P); and right-left (R-L). In the 20 patients who underwent analysis of self-breath-holding, mean maximum difference in tumor position obtained under breath-hold using the Active and the Passive modes were: 2.2 and 3.1 mm along the C-C axis; 1.4 and 2.4 mm along the A-P axis; and 1.3 and 2.2 mm along the R-L axis, respectively. These differences in all axes were significantly smaller (p<0.05) for the Active mode than for the Passive mode. Most tumors displayed maximal respiratory movement along the C-C axis, and minimal movement along the R-L axis, but tumors located in the upper lung displayed maximal movement along the A-P axis. Significant correlation (p<0.05) was observed between differences along three axes in either mode of breath-hold. In conclusion, the reproducibility of tumor position under self-breath-holding by patients during deep inspiration after sufficient practice and in the absence of respiratory monitoring devices was satisfactorily accurate, and differences in tumor position were smaller under breath-holding using the Active mode than using the Passive mode. We believe this new technique is likely to prove extremely useful for the irradiation of lung tumors with a small internal margin and for reduced proportion of high-dose irradiated normal lung to total lung volume.

A method for the reconstruction of four-dimensional synchronized CT scans acquired during free breathing

Breathing motion is a significant source of error in radiotherapy treatment planning for the thorax and upper abdomen. Accounting for breathing motion has a profound effect on the size of conformal radiation portals employed in these sites. Breathing motion also causes artifacts and distortions in treatment planning computed tomography (CT) scans acquired during free breathing and also causes a breakdown of the assumption of the superposition of radiation portals in intensity-modulated radiation therapy, possibly leading to significant dose delivery errors. Proposed voluntary and involuntary breath-hold techniques have the potential for reducing or eliminating the effects of breathing motion, however, they are limited in practice, by the fact that many lung cancer patients cannot tolerate holding their breath. We present an alternative solution to accounting for breathing motion in radiotherapy treatment planning, where multislice CT scans are collected simultaneously with digital spirometry over many free breathing cycles to create a four-dimensional (4-D) image set, where tidal lung volume is the additional dimension. An analysis of this 4-D data leads to methods for digital-spirometry, based elimination or accounting of breathing motion artifacts in radiotherapy treatment planning for free breathing patients. The 4-D image set is generated by sorting free-breathing multislice CT scans according to user-defined tidal-volume bins. A multislice CT scanner is operated in the ciné mode, acquiring 15 scans per couch position, while the patient undergoes simultaneous digital-spirometry measurements. The spirometry is used to retrospectively sort the CT scans by their correlated tidal lung volume within the patient's normal breathing cycle. This method has been prototyped using data from three lung cancer patients. The actual tidal lung volumes agreed with the specified bin volumes within standard deviations ranging between 22 and 33 cm3. An analysis of sagittal and coronal images demonstrated relatively small (<1 cm) motion artifacts along the diaphragm, even for tidal volumes where the rate of breathing motion is greatest. While still under development, this technology has the potential for revolutionizing the radiotherapy treatment planning for the thorax and upper abdomen.

Elective nodal failures are uncommon in medically inoperable patients with Stage I non-small-cell lung carcinoma treated with limited radiotherapy fields

PURPOSE

To review the outcome for 56 Stage I non-small-cell lung cancer treated definitively with three-dimensional conformal radiotherapy (3D-CRT) and to investigate the value of elective nodal irradiation in this patient population.

METHODS AND MATERIALS

Between 1992 and 2001, 56 patients were treated with 3D-CRT for inoperable Stage I histologically confirmed non-small-cell lung cancer; 31 with T1N0 and 25 with T2N0 disease. All patients were treated with 3D-CRT to a median isocenter dose of 70 Gy (range 59.94-83.85) given in daily doses of 1.8 or 2 Gy. Prognostic factors were analyzed with respect to their impact on overall survival. Twenty-two patients received radiotherapy (RT) directed to elective regional lymphatics to doses of 45-50 Gy. The remaining 33 patients were treated to limited fields confined to the primary lung cancer with a margin. The patterns of failure were reviewed.

RESULTS

The median follow-up was 20 months (range 6 months to 6 years). The actuarial local control rate was 88%, 69%, and 63%, at 1, 2, and 3 years, respectively. The actuarial cause-specific survival rate was 82%, 67%, and 51% at 1, 2, and 3 years, respectively. The actuarial overall survival rate was 73%, 51%, and 34% at 1, 2, and 3 years, respectively. The actuarial metastasis-free survival rate was 90%, 85%, and 81% at 1, 2, and 3 years, respectively. The RT dose was the only factor predictive of overall survival in our analysis. No statistically significant difference was noted in cause-specific or overall survival according to whether patients received elective nodal irradiation. Two of 33 patients treated with limited fields had regional nodal failure.

CONCLUSION

Many patients with medically inoperable Stage I lung cancer die of intercurrent causes. The omission of the elective nodal regions from the RT portals did not compromise either the cause-specific or overall survival rate. Elective nodal failures were uncommon in the group treated with limited RT fields. A radiation dose 70 Gy was predictive of better survival in our population. We await the results of prospective trials evaluating high-dose RT in patients treated with RT alone for Stage I lung cancer.

Tumor location cannot predict the mobility of lung tumors: a 3D analysis of data generated from multiple CT scans

PURPOSE

There is limited information available on the three-dimensional (3D) motion of lung tumors. Data derived from multiple planning computed tomographic (CT) scans were used to characterize the 3D movement of small peripheral lung tumors.

METHODS AND MATERIALS

A total of 29 data sets from patients with Stage I non-small-cell lung cancer (NSCLC), each of which consisted of three "rapid" and three "slow" planning CT scans, were analyzed. All six scans were coregistered, and contoured gross tumor volumes (GTVs) were expanded by 5 mm to derive clinical target volumes (CTVs). Two-dimensional and 3D displacement vectors of the individual CTVs, relative to an "optimal" CTV derived from all six scans, were generated. Tumor mobility was correlated with location. Three-dimensional margins, which had to be added to individual CTVs to ensure coverage of "optimal" CTVs, were determined.

RESULTS

No significant correlation was observed between the anatomic location of tumors and the extent of mobility in the x, y, and z axes. However, supradiaphragmatic lesions exhibited more mobility, particularly in the craniocaudal direction. The addition of a 3D margin of 5 mm to a single slow CTV ensured full coverage of the "optimal CTV".

CONCLUSIONS

Lung tumors demonstrate significant mobility in all directions, and this did not closely correlate with anatomic location. Individualized assessment of tumor mobility remains necessary, and is possible when the CTV derived from a single slow scan is used for radiotherapy planning.

Lung cancer 5: state of the art radiotherapy for lung cancer

Radiotherapy has a key role in curative and palliative treatments of patients with lung cancer. Important advances are described in the technique of treatment delivery and its integration with chemotherapy.

A new irradiation system for lung cancer combining linear accelerator, computed tomography, patient self-breath-holding, and patient-directed beam-control without respiratory monitoring devices

PURPOSE

To introduce and assess a new irradiation technique for lung cancer that utilizes a linear accelerator and computed tomography (CT) scanner combination, along with a novel switching mechanism, which enables patients to synchronize the duration of irradiation with self-breath-holding without respiratory monitoring devices.

MATERIALS AND METHODS

A newly developed treatment unit, a linear accelerator combined with a CT scanner (CT-linac), was used for irradiation. A novel switching mechanism, connected directly to the console of the linear accelerator, enabled the patient to control the radiation beam to correspond with the duration of self-breath-holding during a session determined by a radiation technologist. Twenty patients with lung cancer were enrolled in this study. All patients were instructed in the technique of breath-holding during the inspiration phase using visualization of respiratory motion through fluoroscopy as a teaching aid. CT scans under patients' self-breath-holding were repeated three times, and differences in tumor position on CT images were measured. The reproducibility of tumor position was visually evaluated on electronic portal images (EPI).

RESULTS

Mean maximum differences in tumor position under patients' self-breath-holding were 2.2 mm in the cranial-caudal direction, 1.4 mm in the anterior-posterior direction, and 1.3 mm in the right-left direction. Switching of the radiation beam was delayed less than 0.1 s behind patient switching. EPIs were used to determine that reproducibility of tumor position was satisfactorily accurate.

CONCLUSIONS

The reproducibility of tumor position, during patient self-breath-holding synchronized with patient-initiated radiation and without a respiratory monitoring device, was sufficiently accurate. This novel irradiation technique for lung tumors using a combination CT-linac offers reduced PTV, sufficient reproducibility, and decreased duration of treatment.

Are multiple CT scans required for planning curative radiotherapy in lung tumors of the lower lobe?

PURPOSE

Lung tumors located in the lower lobe are the most mobile. Multiple computed tomographic (CT) scans, which had been performed for radiotherapy planning, were analyzed to determine the minimal number of required scans.

METHODS AND MATERIALS

Six spiral CT scans (3 rapid and 3 slow) from 7 such patients were coregistered. Reproducibility of target volumes was defined as the ratio between the overlapping and encompassing volume (COM/SUM) from scans derived using one technique. Volumetric and dosimetric analyses were performed.

RESULTS

Slow CT scans generated larger and more reproducible target volumes than rapid planning scans, with a mean COM/SUM ratio of 71.9 +/- 8.7% and 58.0 +/- 12.7%, respectively. When only a single slow CT scan was used for planning, the addition of a symmetrical 3D margin of 5 mm ensured 99% coverage of the "optimal" target volume, which was derived from summation of target volumes from all six scans.

CONCLUSION

Planning target volumes (PTVs) derived from a single slow CT scan plus a 5-mm margin covered the "optimal" PTVs generated from six scans. Although these "slow PTVs" were larger, the increase in V(20) (the volume of lung tissue receiving a dose > or = 20 Gy) was limited. This indicates that only two CT scans, i.e., a full rapid scan of the entire thorax and a limited slow scan, are necessary for treatment planning in peripheral lung cancers.

Quantifying the effect of intrafraction motion during breast IMRT planning and dose delivery

Respiratory motion during intensity modulated radiation therapy (IMRT) causes two types of problems. First, the clinical target volume (CTV) to planning target volume (PTV) margin needed to account for respiratory motion means that the lung and heart dose is higher than would occur in the absence of such motion. Second, because respiratory motion is not synchronized with multileaf collimator (MLC) motion, the delivered dose is not the same as the planned dose. The aims of this work were to evaluate these problems to determine (a) the effects of respiratory motion and setup error during breast IMRT treatment planning, (b) the effects of the interplay between respiratory motion and multileaf collimator (MLC) motion during breast IMRT delivery, and (c) the potential benefits of breast IMRT using breath-hold, respiratory gated, and 4D techniques. Seven early stage breast cancer patient data sets were planned for IMRT delivered with a dynamic MLC (DMLC). For each patient case, eight IMRT plans with varying respiratory motion magnitudes and setup errors (and hence CTV to PTV margins) were created. The effects of respiratory motion and setup error on the treatment plan were determined by comparing the eight dose distributions. For each fraction of these plans, the effect of the interplay between respiratory motion and MLC motion during IMRT delivery was simulated by superimposing the respiratory trace on the planned DMLC leaf motion, facilitating comparisons between the planned and expected dose distributions. When considering respiratory motion in the CTV-PTV expansion during breast IMRT planning, our results show that PTV dose heterogeneity increases with respiratory motion. Lung and heart doses also increase with respiratory motion. Due to the interplay between respiratory motion and MLC motion during IMRT delivery, the planned and expected dose distributions differ. This difference increases with respiratory motion. The expected dose varies from fraction to fraction. However, for the seven patients studied and respiratory trace used, for no breathing, shallow breathing, and normal breathing, there were no statistically significant differences between the planned and expected dose distributions. Thus, for breast IMRT, intrafraction motion degrades treatment plans predominantly by the necessary addition of a larger CTV to PTV margin than would be required in the absence of such motion. This motion can be limited by breath-hold, respiratory gated, or 4D techniques.

Concurrent two-dimensional radiotherapy and weekly docetaxel in the treatment of stage III non-small cell lung cancer: a good local response but no good survival due to radiation pneumonitis

Docetaxel is a novel, potentially highly beneficial drug for the treatment of lung cancer, and has shown remarkable radio-sensitizing effects in vitro. In the present study, we evaluated whether weekly docetaxel (20 mg/m(2)) and conventionally fractionated radiotherapy with the two-dimensional (2D) technique could be tolerated and effective in the treatment of locally advanced non-small-cell lung cancer (NSCLC). Thirty-two stage III (IIIA:13, IIIB:19) NSCLC patients were treated with weekly administration of docetaxel (20 mg/m(2)) on days 1, 8, 15, 22, 29 and 36 in addition to concurrent radiation therapy. The total tumor dose was 60-66 Gy given with a 2D technique in 6-7 weeks. Complete response was observed in 9/32 (28%) patients and partial response in 20/32 (63%). Three (9%) patients died of chemoradiation-induced pneumonitis after completion of therapy. In total, grade >3 toxicities included pneumonitis (47%) and esophagitis (16%). The median overall survival duration was 12 months. The dimensions of the radiotherapy port were larger in patients who produced severe (grade >3) chemoradiation pneumonitis than in patients who did not (P<0.05). The median survival time was 12.4 months and 2-year overall survival were 35%. The survival was better in patients whose first radiotherapy port dimensions were less than 150 cm(2) compared to patients whose first radiation port dimensions were >==150 cm(2) (P<0.05). In conclusion, concurrent weekly administration of docetaxel (20 mg/m(2)) with 2D radiotherapy for NSCLC, had good local response, but survival rate was not completely satisfactory due to chemoradiation pneumonitis, which was the principal toxicity that adversely affected prognosis in elderly patients whose radiotherapy port was large.

Quantifying the predictability of diaphragm motion during respiration with a noninvasive external marker

The aim of this work was to quantify the ability to predict intrafraction diaphragm motion from an external respiration signal during a course of radiotherapy. The data obtained included diaphragm motion traces from 63 fluoroscopic lung procedures for 5 patients, acquired simultaneously with respiratory motion signals (an infrared camera-based system was used to track abdominal wall motion). During these sessions, the patients were asked to breathe either (i) without instruction, (ii) with audio prompting, or (iii) using visual feedback. A statistical general linear model was formulated to describe the relationship between the respiration signal and diaphragm motion over all sessions and for all breathing training types. The model parameters derived from the first session for each patient were then used to predict the diaphragm motion for subsequent sessions based on the respiration signal. Quantification of the difference between the predicted and actual motion during each session determined our ability to predict diaphragm motion during a course of radiotherapy. This measure of diaphragm motion was also used to estimate clinical target volume (CTV) to planning target volume (PTV) margins for conventional, gated, and proposed four-dimensional (4D) radiotherapy. Results from statistical analysis indicated a strong linear relationship between the respiration signal and diaphragm motion (p<0.001) over all sessions, irrespective of session number (p=0.98) and breathing training type (p=0.19). Using model parameters obtained from the first session, diaphragm motion was predicted in subsequent sessions to within 0.1 cm (1 sigma) for gated and 4D radiotherapy. Assuming a 0.4 cm setup error, superior-inferior CTV-PTV margins of 1.1 cm for conventional radiotherapy could be reduced to 0.8 cm for gated and 4D radiotherapy. The diaphragm motion is strongly correlated with the respiration signal obtained from the abdominal wall. This correlation can be used to predict diaphragm motion, based on the respiration signal, to within 0.1 cm (1 sigma) over a course of radiotherapy.

Synchronized moving aperture radiation therapy (SMART): average tumour trajectory for lung patients

Synchronized moving aperture radiation therapy (SMART) is a new technique for treating mobile tumours under development at Massachusetts General Hospital (MGH). The basic idea of SMART is to synchronize the moving radiation beam aperture formed by a dynamic multileaf collimator (DMLC) with the tumour motion induced by respiration. SMART is based on the concept of the average tumour trajectory (ATT) exhibited by a tumour during respiration. During the treatment simulation stage, tumour motion is measured and the ATT is derived. Then, the original IMRT MLC leaf sequence is modified using the ATT to compensate for tumour motion. During treatment, the tumour motion is monitored. The treatment starts when leaf motion and tumour motion are synchronized at a specific breathing phase. The treatment will halt when the tumour drifts away from the ATT and will resume when the synchronization between tumour motion and radiation beam is re-established. In this paper, we present a method to derive the ATT from measured tumour trajectory data. We also investigate the validity of the ATT concept for lung tumours during normal breathing. The lung tumour trajectory data were acquired during actual radiotherapy sessions using a real-time tumour-tracking system. SMART treatment is simulated by assuming that the radiation beam follows the derived ATT and the tumour follows the measured trajectory. In simulation, the treatment starts at exhale phase. The duty cycle of SMART delivery was calculated for various treatment times and gating thresholds, as well as for various exhale phases where the treatment begins. The simulation results show that in the case of free breathing, for 4 out of 11 lung datasets with tumour motion greater than 1 cm from peak to peak, the error in tumour tracking can be controlled to within a couple of millimetres while maintaining a reasonable delivery efficiency. That is to say, without any breath coaching/control, the ATT is a valid concept for some lung tumours. However, to make SMART an efficient technique in general, it is found that breath coaching techniques are required.

Respiratory gating for liver tumors: use in dose escalation

PURPOSE

To determine the clinical impact of the Varian Real-Time Position Monitor (RPM) respiratory gating system for treatment of liver tumors.

METHODS AND MATERIALS

Ten patients with liver tumors were selected for evaluation of this passive system, which tracks motion of reflective markers mounted on the abdomen with an infrared-sensitive camera. At simulation, a fluoroscopic movie, breathing trace, and CT scans synchronized at end-expiration (E-E) and end-inspiration were acquired in treatment position using the RPM system. Organs and gross tumor volume were contoured on each CT. Each organ's positional change between two scan sets was quantified by calculation of the center of volume shift and an "index coefficient," defined as the volume common to the two versions of the organ to the volume included in at least one (intersection/union). Treatment dose was determined by use of normal tissue complication probability calculations and dose-volume histograms. Gated portal images were obtained to monitor gating reproducibility with treatment.

RESULTS

Eight patients received 177 treatments with RPM gating. Average superior-to-inferior (SI) diaphragm motion on initial fluoroscopy was reduced from 22.7 mm without gating to 5.1 mm with gating. Comparing end-inspiration to E-E CT scans, average SI movement of the right diaphragm was 11.5 mm vs. 2.2 mm for two E-E CT scans. For all organs, average E-I SI organ motion was 12.8 mm vs. 2.0 mm for E-E studies. Index coefficients were closer to 1.0 for E-E than end-inspiration scans, indicating gating reproducibility. The average SI displacement of diaphragm apex on gated portal images compared with DRR was 2.3 mm. Treatment was prolonged less than 10 minutes with gating. The reproducible decrease in organ motion with gating enabled reduction in gross tumor volume-to-planning target volume margin from 2 to 1 cm. This allowed for calculated dose increases of 7%-27% (median: 21.3%) in 6 patients and enabled treatment in 2.

CONCLUSION

Gating of radiotherapy for liver tumors enables safe margin reduction on tumor volume, which, in turn, may allow for dose escalation.

[Thoracic radiotherapy and control of respiration: current perspectives]

Three-dimensional conformal radiotherapy (3D CRT) is adversely affected by setup error and organ motion. In thoracic 3D CRT, breathing accounts for most of intra-fraction movements, thus impairing treatment quality. Breath control clearly exhibits dosimetric improvement compared to free breathing, leading to various techniques for gated treatments. We review benefits of different breath control methods--i.e. breath-holding or beam gating, with spirometric, isometric or X-ray respiration sensor--and argument the choice of expiration versus inspiration, with consideration to dosimetric concerns. All steps of 3D-CRT can be improved with breath control. Contouring of organs at risk (OAR) and target are easier and more accurate on breath controlled CT-scans. Inter- and intra-fraction target immobilisation allows smaller margins with better coverage. Lung outcome predictors (NTCP, Mean Dose, LV20, LV30) are improved with breath-control. In addition, inspiration breath control facilitates beam arrangement since it widens the distance between OAR and target, and leaves less lung normal tissue within the high dose region. Last, lung density, as of CT-scan, is more accurate, improving dosimetry. Our institution's choice is to use spirometry driven, patient controlled high-inspiration breath-hold; this technique gives excellent immobilization results, with high reproducibility, yet it is easy to implement and costs little extra treatment time. Breath control, whatever technique is employed, proves superior to free breathing treatment when using 3D-CRT. Breath control should then be used whenever possible, and is probably mandatory for IMRT.

[Non-small-cell bronchial cancers: improvement of survival probability by conformal radiotherapy]

The conformal radiotherapy approach, three-dimensional conformal radiotherapy (3DCRT) and intensity-modulated radiotherapy (IMRT), is based on modern imaging modalities, efficient 3D treatment planning systems, sophisticated immobilization devices and demanding quality assurance and treatment verification. The main goal of conformal radiotherapy is to ensure a high dose distribution tailored to the limits of the target volume while reducing exposure of healthy tissues. These techniques would then allow a further dose escalation increasing local control and survival. Non-small cell lung cancer (NSCLC) is one of the most difficult malignant tumors to be treated. It combines geometrical difficulties due to respiratory motion, and number of low tolerance neighboring organs, and dosimetric difficulties because of the presence of huge inhomogeneities. This localization is an attractive and ambitious example for the evaluation of new techniques. However, the published clinical reports in the last years described very heterogeneous techniques and, in the absence of prospective randomized trials, it is somewhat difficult at present to evaluate the real benefits drawn from those conformal radiotherapy techniques. After reviewing the rationale for 3DCRT for NSCLC, this paper will describe the main studies of 3DCRT, in order to evaluate its impact on lung cancer treatment. Then, the current state-of-the-art of IMRT and the last technical and therapeutic innovations in NSCLC will be discussed.

Precise and real-time measurement of 3D tumor motion in lung due to breathing and heartbeat, measured during radiotherapy

PURPOSE

In this work, three-dimensional (3D) motion of lung tumors during radiotherapy in real time was investigated. Understanding the behavior of tumor motion in lung tissue to model tumor movement is necessary for accurate (gated or breath-hold) radiotherapy or CT scanning.

METHODS

Twenty patients were included in this study. Before treatment, a 2-mm gold marker was implanted in or near the tumor. A real-time tumor tracking system using two fluoroscopy image processor units was installed in the treatment room. The 3D position of the implanted gold marker was determined by using real-time pattern recognition and a calibrated projection geometry. The linear accelerator was triggered to irradiate the tumor only when the gold marker was located within a certain volume. The system provided the coordinates of the gold marker during beam-on and beam-off time in all directions simultaneously, at a sample rate of 30 images per second. The recorded tumor motion was analyzed in terms of the amplitude and curvature of the tumor motion in three directions, the differences in breathing level during treatment, hysteresis (the difference between the inhalation and exhalation trajectory of the tumor), and the amplitude of tumor motion induced by cardiac motion.

RESULTS

The average amplitude of the tumor motion was greatest (12 +/- 2 mm [SD]) in the cranial-caudal direction for tumors situated in the lower lobes and not attached to rigid structures such as the chest wall or vertebrae. For the lateral and anterior-posterior directions, tumor motion was small both for upper- and lower-lobe tumors (2 +/- 1 mm). The time-averaged tumor position was closer to the exhale position, because the tumor spent more time in the exhalation than in the inhalation phase. The tumor motion was modeled as a sinusoidal movement with varying asymmetry. The tumor position in the exhale phase was more stable than the tumor position in the inhale phase during individual treatment fields. However, in many patients, shifts in the exhale tumor position were observed intra- and interfractionally. These shifts are the result of patient relaxation, gravity (posterior direction), setup errors, and/or patient movement.The 3D trajectory of the tumor showed hysteresis for 10 of the 21 tumors, which ranged from 1 to 5 mm. The extent of hysteresis and the amplitude of the tumor motion remained fairly constant during the entire treatment. Changes in shape of the trajectory of the tumor were observed between subsequent treatment days for only one patient. Fourier analysis revealed that for 7 of the 21 tumors, a measurable motion in the range 1-4 mm was caused by the cardiac beat. These tumors were located near the heart or attached to the aortic arch. The motion due to the heartbeat was greatest in the lateral direction. Tumor motion due to hysteresis and heartbeat can lower treatment efficiency in real-time tumor tracking-gated treatments or lead to a geographic miss in conventional or active breathing controlled treatments.

CONCLUSION

The real-time tumor tracking system measured the tumor position in all three directions simultaneously, at a sampling rate that enabled detection of tumor motion due to heartbeat as well as hysteresis. Tumor motion and hysteresis could be modeled with an asymmetric function with varying asymmetry. Tumor motion due to breathing was greatest in the cranial-caudal direction for lower-lobe unfixed tumors.

Evaluation of deep inspiration breath-hold lung treatment plans with Monte Carlo dose calculation

PURPOSE

To evaluate dosimetry of deep inspiration breath-hold (DIBH) relative to free breathing (FB) for three-dimensional conformal radiation therapy of lung cancer with 6-MV photons and Monte Carlo (MC) dose calculations.

METHODS AND MATERIALS

Static three-dimensional conformal radiation therapy, 6-MV plans, based on DIBH and FB CT images for five non-small-cell lung cancer patients, were generated on a clinical treatment planning system with equivalent path length tissue inhomogeneity correction. Margins of gross to planning target volume were not reduced for DIBH plans. Cord and lung toxicity determined the maximum treatment dose for each plan. Dose distributions were recalculated for the same beams with an MC dose calculation algorithm and electron density distributions derived from the CT images.

RESULTS

MC calculations showed decreased target coverage relative to treatment-planning system predictions. Lateral disequilibrium caused more degradation of target coverage for DIBH than for FB (approximately 4% worse than expected for FB vs. 8% for DIBH). However, with DIBH higher treatment doses could be delivered without violating normal tissue constraints, resulting in higher total doses to gross target volume and to >99% of planning target volume.

CONCLUSIONS

If DIBH enables prescription dose increases exceeding 10%, MC calculations indicate that, despite lateral disequilibrium, higher doses will be delivered to medium-to-large, partly mediastinal gross target volumes, providing that 6-MV photons are used and margins are not reduced.

Dose-volume specification: new challenges with intensity-modulated radiation therapy

It has long been recognized that the specification of volumes and doses is an important issue for radiation oncology. Although in any individual center, policies and procedures of treatment delivery may be well understood by staff, reporting of treatment techniques in the archival literature in an unambiguous manner has been found to be less than desirable in many instances. For clinical studies utilizing three-dimensional conformal radiation therapy (3D-CRT), and even more so, intensity-modulated radiation therapy (IMRT), the situation has become even more complex. 3D-CRT and IMRT are now recognized to be more sensitive to geometric uncertainties than conventional radiation therapy because of their ability to create sharper dose gradients around target volumes and organs at risk (OARs). This article reviews the current status of specifying target volumes and doses for 3D-CRT and IMRT, and discusses some of the pertinent issues regarding the use of recommendations in Reports 50 and 62 of the International Commission on Radiation Units and Measurements (ICRU) in this task. It is imperative that physician and physicist fully appreciate the need to account for clinical and spatial uncertainties in the planning and delivery of cancer patients' treatment, paying even more attention to these issues for those cases in which 3D-CRT and/or IMRT is used. A brief review of the reporting requirements for Radiation Therapy Oncology Group (RTOG) 3D-CRT and IMRT protocols is also presented.

The effectiveness of breath-holding to stabilize lung and pancreas tumors during radiosurgery

PURPOSE

To evaluate the effect of breath-holding on the short-term reproducibility and long-term variability of tumor position during image-guided radiosurgery.

METHOD

Thirteen patients have undergone single-fraction radiosurgery treatments during which the tumor was repeatedly imaged radiographically to observe its position. The imaging data were used to monitor the efficacy of breath-holding and to periodically readjust the alignment of the treatment beam with the tumor. These measurements have allowed the effects of breathing, heartbeat, patient movement, and instrumental uncertainties to be separately identified in the record of tumor position.

RESULTS

During inspiration breath-holding, the lung tumor position was reproducible to within 1 mm, on average, in the direction of maximum displacement during regular breathing, and to within 1.8 mm in three dimensions overall. The pancreas tumor position in three dimensions was reproducible to within 2.5 mm on average. Some patients showed a slow, steady drift of tumor position during the extended sequence of breath-holds, which was compensated by periodic retargeting of the treatment beam.

CONCLUSION

Breath-holding can allow the reduction of tumor motion dosimetry margins to 2 mm or less for lung cancer treatments, provided that the treatment system can detect and adapt to long-term variations in the mean tumor position during a lengthy treatment fraction.

Has 3-D conformal radiotherapy (3D CRT) improved the local tumour control for stage I non-small cell lung cancer?

AIMS AND BACKGROUND

The high local failure rates observed after radiotherapy in stage I non-small cell lung cancer (NSCLC) may be improved by the use of 3-dimensional conformal radiotherapy (3D CRT).

MATERIALS AND METHODS

The case-records of 113 patients who were treated with curative 3D CRT between 1991 and 1999 were analysed. No elective nodal irradiation was performed, and doses of 60Gy or more, in once-daily fractions of between 2 and 3Gy, were prescribed.

RESULTS

The median actuarial survival of patients was 20 months, with 1-, 3- and 5-year survival of 71, 25 and 12%, respectively. Local disease progression was the cause of death in 30% of patients, and 22% patients died from distant metastases. Grade 2-3 acute radiation pneumonitis (SWOG) was observed in 6.2% of patients. The median actuarial local progression-free survival (LPFS) was 27 months, with 85 and 43% of patients free from local progression at 1 and 3 years, respectively. Endobronchial tumour extension significantly influenced LPFS, both on univariate (P=0.023) and multivariate analysis (P=0.023). The median actuarial cause-specific survival (CSS) was 19 months, and the respective 1- and 3-year rates were 72 and 30%. Multivariate analysis showed T2 classification (P=0.017) and the presence of endobronchial tumour extension (P=0.029) to be adverse prognostic factors for CSS. On multivariate analysis, T-stage significantly correlated with distant failure (P=0.005).

CONCLUSIONS

Local failure rates remain substantial despite the use of 3D CRT for stage I NSCLC. Additional improvements in local control can come about with the use of radiation dose escalation and approaches to address the problem of tumour mobility.

Issues in respiratory motion compensation during external-beam radiotherapy

PURPOSE

To investigate how respiration influences the motion of lung and pancreas tumors and to relate the observations to treatment procedures intended to improve dose alignment by predicting the moving tumor's position from external breathing indicators.

METHODS AND MATERIALS

Breathing characteristics for five healthy subjects were observed by optically tracking the displacement of the chest and abdomen, and by measuring tidal air volume with a spirometer. Fluoroscopic imaging of five radiotherapy patients detected the motion of lung and pancreas tumors synchronously with external breathing indicators.

RESULTS

The external and fluoroscopic data showed a wide range of behavior in the normal breathing pattern and its effects on the position of lung and pancreas tumors. This included transient phase shifts between two different external measures of breathing that diminished to zero over a period of minutes, modulated phase shifts between tumor and chest wall motion, and other complex phenomena.

CONCLUSIONS

Respiratory compensation strategies that infer tumor position from external breathing signals, including methods of beam gating and dynamic beam tracking, require three-dimensional knowledge of the tumor's motion trajectory as well as the ability to detect and adapt to transient and continuously changing characteristics of respiratory motion during treatment.

Potential radiotherapy improvements with respiratory gating

Gating is a relatively new and potentially useful therapeutic addition to external beam radiotherapy applied to regions affected by intra-fraction motion. The impact was of gating on treatment margins, image artifacts, and volume and positional accuracy was investigated by CT imaging of sinusoidally moving spheres. The motion of the spheres simulates target motion. During the CT imaging of dynamically moving spheres, gating reproduced the static volume to within 1%, whereas errors of over 20% were observed where gating was not used. Using a theoretical analysis of margins, gating alone or in combination with an electronic portal imaging device may allow a 2-11 mm reduction in the CTV to PTV margin, and thus less healthy tissue need be irradiated. Gating may allow a reduction of treatment margins, an improvement in image quality, and an improvement in positional and volumetric accuracy of the gross tumor volume.

[Radiotherapy of lung cancer: the inspiration breath hold with spirometric monitoring]

A CT acquisition during a free breathing examination generates images of poor quality. It creates an uncertainty on the reconstructed gross tumour volume and dose distribution. The aim of this study is to test the feasibility of a breath hold method applied in all preparation and treatment days. Five patients received a thoracic radiotherapy with the benefit of this procedure. The breathing of the patient was measured with a spirometer. The patient was coached to reproduce a constant level of breath-hold in a deep inspiration. Video glasses helped the patients to fix the breath-hold at the reference level. The patients followed the coaching during preparation and treatment, without any difficulty. The better quality of the CT reconstructed images resulted in an easier contouring. No movements of the gross tumour volume lead to a better coverage. The deep breath hold decreased the volume of irradiated lung. This method improves the reproducibility of the thoracic irradiation. The decrease of irradiated lung volume offers prospects in dose escalation and intensity modulation radiotherapy.

Dosimetric advantage of using 6 MV over 15 MV photons in conformal therapy of lung cancer: Monte Carlo studies in patient geometries

Many lung cancer patients who undergo radiation therapy are treated with higher energy photons (15-18 MV) to obtain deeper penetration and better dose uniformity. However, the longer range of the higher energy recoil electrons in the low-density medium may cause lateral electronic disequilibrium and degrade the target coverage. To compare the dose homogeneity achieved with lower versus higher energy photon beams, we performed a dosimetric study of 6 and 15 MV three-dimensional (3D) conformal treatment plans for lung cancer using an accurate, patient-specific dose-calculation method based on a Monte Carlo technique. A 6 and 15 MV 3D conformal treatment plan was generated for each of two patients with target volumes exceeding 200 cm(3) on an in-house treatment planning system in routine clinical use. Each plan employed four conformally shaped photon beams. Each dose distribution was recalculated with the Monte Carlo method, utilizing the same beam geometry and patient-specific computed tomography (CT) images. Treatment plans using the two energies were compared in terms of their isodose distributions and dose-volume histograms (DVHs). The 15 MV dose distributions and DVHs generated by the clinical treatment planning calculations were as good as, or slightly better than, those generated for 6 MV beams. However, the Monte Carlo dose calculation predicted increased penumbra width with increased photon energy resulting in decreased lateral dose homogeneity for the 15 MV plans. Monte Carlo calculations showed that all target coverage indicators were significantly worse for 15 MV than for 6 MV; particularly the portion of the planning target volume (PTV) receiving at least 95% of the prescription dose (V(95)) dropped dramatically for the 15 MV plan in comparison to the 6 MV. Spinal cord and lung doses were clinically equivalent for the two energies. In treatment planning of tumors that abut lung tissue, lower energy (6 MV) photon beams should be preferred over higher energies (15-18 MV) because of the significant loss of lateral dose equilibrium for high-energy beams in the low-density medium. Any gains in radial dose uniformity across steep density gradients for higher energy beams must be weighed carefully against the lateral beam degradation due to penumbra widening.

The reproducibility of organ position using active breathing control (ABC) during liver radiotherapy

PURPOSE

To evaluate the intrafraction and interfraction reproducibility of liver immobilization using active breathing control (ABC).

METHODS AND MATERIALS

Patients with unresectable intrahepatic tumors who could comfortably hold their breath for at least 20 s were treated with focal liver radiation using ABC for liver immobilization. Fluoroscopy was used to measure any potential motion during ABC breath holds. Preceding each radiotherapy fraction, with the patient setup in the nominal treatment position using ABC, orthogonal radiographs were taken using room-mounted diagnostic X-ray tubes and a digital imager. The radiographs were compared to reference images using a 2D alignment tool. The treatment table was moved to produce acceptable setup, and repeat orthogonal verification images were obtained. The positions of the diaphragm and the liver (assessed by localization of implanted radiopaque intra-arterial microcoils) relative to the skeleton were subsequently analyzed. The intrafraction reproducibility (from repeat radiographs obtained within the time period of one fraction before treatment) and interfraction reproducibility (from comparisons of the first radiograph for each treatment with a reference radiograph) of the diaphragm and the hepatic microcoil positions relative to the skeleton with repeat breath holds using ABC were then measured. Caudal-cranial (CC), anterior-posterior (AP), and medial-lateral (ML) reproducibility of the hepatic microcoils relative to the skeleton were also determined from three-dimensional alignment of repeat CT scans obtained in the treatment position.

RESULTS

A total of 262 fractions of radiation were delivered using ABC breath holds in 8 patients. No motion of the diaphragm or hepatic microcoils was observed on fluoroscopy during ABC breath holds. From analyses of 158 sets of positioning radiographs, the average intrafraction CC reproducibility (sigma) of the diaphragm and hepatic microcoil position relative to the skeleton using ABC repeat breath holds was 2.5 mm (range 1.8-3.7 mm) and 2.3 mm (range 1.2-3.7 mm) respectively. However, based on 262 sets of positioning radiographs, the average interfraction CC reproducibility (sigma) of the diaphragm and hepatic microcoils was 4.4 mm (range 3.0-6.1 mm) and 4.3 mm (range 3.1-5.7 mm), indicating a change of diaphragm and microcoil position relative to the skeleton over the course of treatment with repeat breath holds at the same phase of the respiratory cycle. The average population absolute intrafraction CC offset in diaphragm and microcoil position relative to skeleton was 2.4 mm and 2.1 mm respectively; the average absolute interfraction CC offset was 5.2 mm. Analyses of repeat CT scans demonstrated that the average intrafraction excursion of the hepatic microcoils relative to the skeleton in the CC, AP, and ML directions was 1.9 mm, 0.6 mm, and 0.6 mm respectively and the average interfraction CC, AP, and ML excursion of the hepatic microcoils was 6.6 mm, 3.2 mm, and 3.3 mm respectively.

CONCLUSION

Radiotherapy using ABC for patients with intrahepatic cancer is feasible, with good intrafraction reproducibility of liver position using ABC. However, the interfraction reproducibility of organ position with ABC suggests the need for daily on-line imaging and repositioning if treatment margins smaller than those required for free breathing are a goal.

Multiple "slow" CT scans for incorporating lung tumor mobility in radiotherapy planning

PURPOSE

The high local recurrence rates after radiotherapy in early-stage lung cancer may be due to geometric errors that arise when target volumes are generated using fast spiral CT scanners. A "slow" CT technique that generates more representative target volumes was evaluated.

METHODS AND MATERIALS

Planning CT scans (slice thickness 3 mm, reconstruction index 2.5 mm) were performed during quiet respiration in 10 patients with peripheral lung lesions. Planning CT scans were repeated twice, followed by three slow CT scans (slice thickness 4 mm, index 3 mm, revolution time 4 s/slice). All, except the first scan, were limited to the tumor region. Three-dimensional registration of all scans was performed. The reproducibility of the imaged volumes was evaluated with each technique using (1) the common overlapping volume (COM), the component of the clinical target volume (CTV) covered by all three CT scans, and (2) the encompassing volume (SUM), which is the volume enveloped by all CTVs.

RESULTS

In all patients, the target volumes generated using slow CT scans were larger than those derived using planning scans (mean ratio of planning-CTV:slow-CTV of 88.8% +/- 5.6%), and also more reproducible. The mean ratio of the respective COM:SUM volumes was 62.6% +/- 10.8% and 54.9% +/- 12.9%.

CONCLUSIONS

Larger, and more reproducible, target volumes are generated for peripheral lung tumors with the use of slow CT scans, thereby indicating that slow scans can better capture tumor movement.

Intensity-modulated radiotherapy: current status and issues of interest

PURPOSE

To develop and disseminate a report aimed primarily at practicing radiation oncology physicians and medical physicists that describes the current state-of-the-art of intensity-modulated radiotherapy (IMRT). Those areas needing further research and development are identified by category and recommendations are given, which should also be of interest to IMRT equipment manufacturers and research funding agencies.

METHODS AND MATERIALS

The National Cancer Institute formed a Collaborative Working Group of experts in IMRT to develop consensus guidelines and recommendations for implementation of IMRT and for further research through a critical analysis of the published data supplemented by clinical experience. A glossary of the words and phrases currently used in IMRT is given in the. Recommendations for new terminology are given where clarification is needed.

RESULTS

IMRT, an advanced form of external beam irradiation, is a type of three-dimensional conformal radiotherapy (3D-CRT). It represents one of the most important technical advances in RT since the advent of the medical linear accelerator. 3D-CRT/IMRT is not just an add-on to the current radiation oncology process; it represents a radical change in practice, particularly for the radiation oncologist. For example, 3D-CRT/IMRT requires the use of 3D treatment planning capabilities, such as defining target volumes and organs at risk in three dimensions by drawing contours on cross-sectional images (i.e., CT, MRI) on a slice-by-slice basis as opposed to drawing beam portals on a simulator radiograph. In addition, IMRT requires that the physician clearly and quantitatively define the treatment objectives. Currently, most IMRT approaches will increase the time and effort required by physicians, medical physicists, dosimetrists, and radiation therapists, because IMRT planning and delivery systems are not yet robust enough to provide totally automated solutions for all disease sites. Considerable research is needed to model the clinical outcomes to allow truly automated solutions. Current IMRT delivery systems are essentially first-generation systems, and no single method stands out as the ultimate technique. The instrumentation and methods used for IMRT quality assurance procedures and testing are not yet well established. In addition, many fundamental questions regarding IMRT are still unanswered. For example, the radiobiologic consequences of altered time-dose fractionation are not completely understood. Also, because there may be a much greater ability to trade off dose heterogeneity in the target vs. avoidance of normal critical structures with IMRT compared with traditional RT techniques, conventional radiation oncology planning principles are challenged. All in all, this new process of planning and treatment delivery has significant potential for improving the therapeutic ratio and reducing toxicity. Also, although inefficient currently, it is expected that IMRT, when fully developed, will improve the overall efficiency with which external beam RT can be planned and delivered, and thus will potentially lower costs.

CONCLUSION

Recommendations in the areas pertinent to IMRT, including dose-calculation algorithms, acceptance testing, commissioning and quality assurance, facility planning and radiation safety, and target volume and dose specification, are presented. Several of the areas in which future research and development are needed are also indicated. These broad recommendations are intended to be both technical and advisory in nature, but the ultimate responsibility for clinical decisions pertaining to the implementation and use of IMRT rests with the radiation oncologist and radiation oncology physicist. This is an evolving field, and modifications of these recommendations are expected as new technology and data become available.

Conformal radiotherapy (CRT) planning for lung cancer: analysis of intrathoracic organ motion during extreme phases of breathing

PURPOSE

Conformal radiotherapy beams are defined on the basis of static computed tomography acquisitions by taking into account setup errors and organ/tumor motion during breathing. In the absence of precise data, the size of the margins is estimated arbitrarily. The objective of this study was to evaluate the amplitude of maximum intrathoracic organ motion during breathing.

METHODS AND MATERIALS

Twenty patients treated for non-small-cell lung cancer were included in the study: 10 patients at the Institut Curie with a personalized alpha cradle immobilization and 10 patients at Tenon Hospital with just the Posirest device below their arms. Three computed tomography acquisitions were performed in the treatment position: the first during free breathing and the other two during deep breath-hold inspiration and expiration. For each acquisition, the displacements of the various intrathoracic structures were measured in three dimensions.

RESULTS

Patients from the two centers were comparable in terms of age, weight, height, tumor site, and stage. In the overall population, the greatest displacements were observed for the diaphragm, and the smallest displacements were observed for the lung apices and carina. The relative amplitude of motion was comparable between the two centers. The use of a personalized immobilization device reduced lateral thoracic movements (p < 0.02) and lung apex movements (p < 0.02).

CONCLUSION

Intrathoracic organ movements during extreme phases of breathing are considerable. Quantification of organ motion is necessary for definition of the safety margins. A personalized immobilization device appears to effectively reduce apical and lateral displacement.

Computed tomographic-pathologic correlation of gross tumor volume and clinical target volume in non-small cell lung cancer: a pilot experience

CONTEXT

Computed tomographic (CT) scan data are used regularly in radiation treatment planning for patients with lung cancer. To our knowledge, the relationship of the CT images of tumors and their corresponding microscopic extent has not yet been studied in detail.

OBJECTIVE

To correlate tumor sizes on CT with tumor sizes measured microscopically (ie, the gross tumor volume [GTV]-clinical target volume margin) in non-small cell lung cancers.

DESIGN

Prospective pilot study.

SETTING

Single institution.

PATIENTS

Patients with operable non-small cell lung cancer were identified preoperatively.

INTERVENTIONS

Once the surgical specimen was available, it was oriented with the surgeon and the pathologist. Seven whole-mount, cross-sectional histologic glass slides were made from 5 tumors using formalin fixation and hematoxylin-eosin staining. The pathologist then outlined the cancer-containing area under the microscope (Micro-GTV) and the area of surrounding inflammatory response (Micro-GTV + inflammation). Preoperative CT scans were used for outlining tumor on the corresponding slice (CT-GTV).

MAIN OUTCOME MEASURES

Correlation of the areas of Micro-GTV, Micro-GTV + inflammation, and CT-GTV was performed.

RESULTS

There was an obvious trend that the CT-GTV was bigger than the Micro-GTV, except in specimen 1, in which the 2 areas were about equal. However, on comparing the values for the CT-GTV and the Micro-GTV + inflammation, the difference between the 2 areas became smaller.

CONCLUSIONS

Modern CT scans might overestimate the GTV in non-small cell lung cancer. The GTV-clinical target volume margin could actually be zero or even a negative value. The findings in this small study are interesting and provoking. Further study with a larger number of patients and more rigid quality control is warranted to confirm our findings.

Three-Dimensional Conformal Radiation Therapy (3D-CRT) for Early-Stage Non–Small-Cell Lung Cancer

The standard treatment for early-stage non-small-cell lung cancer is surgical resection. However, many patients are inoperable due to medical comorbidities. Thirty-two medically inoperable patients with early-stage non-small-cell lung cancer were treated with 3-dimensional conformal radiation therapy between January 1991 and December 2000. The median dose was 70.2 Gy, and the median follow-up time in survivors was 30 months. The 2-year actuarial local control, overall survival, and cancer-specific survival rates were 43%, 54%, and 57%, respectively. The 5-year actuarial local control, overall survival, and cancer-specific survival rates were 43%, 33%, and 39%, respectively. This report suggests that local control is improved with high-dose conformal radiation therapy when compared to other institutions' retrospective experiences.

Determining parameters for respiration-gated radiotherapy

Respiration-gated radiotherapy for tumor sites affected by respiratory motion will potentially improve radiotherapy outcomes by allowing reduced treatment margins leading to decreased complication rates and/or increased tumor control. Furthermore, for intensity-modulated radiotherapy (IMRT), respiratory gating will minimize the hot and cold spot artifacts in dose distributions that may occur as a result of interplay between respiratory motion and leaf motion. Most implementations of respiration gating rely on the real time knowledge of the relative position of the internal anatomy being treated with respect to that of an external marker. A method to determine the amplitude of motion and account for any difference in phase between the internal tumor motion and external marker motion has been developed. Treating patients using gating requires several clinical decisions, such as whether to gate during inhale or exhale, whether to use phase or amplitude tracking of the respiratory signal, and by how much the intrafraction tumor motion can be decreased at the cost of increased delivery time. These parameters may change from patient to patient. A method has been developed to provide the data necessary to make decisions as to the CTV to PTV margins to apply to a gated treatment plan.

Fluoroscopic evaluation of diaphragmatic motion reduction with a respiratory gated radiotherapy system

We report on initial patient studies to evaluate the performance of a commercial respiratory gating radiotherapy system. The system uses a breathing monitor, consisting of a video camera and passive infrared reflective markers placed on the patient's thorax, to synchronize radiation from a linear accelerator with the patient's breathing cycle. Six patients receiving treatment for lung cancer participated in a study of system characteristics during treatment simulation with fluoroscopy. Breathing synchronized fluoroscopy was performed initially without instruction, followed by fluoroscopy with recorded verbal instruction (i.e., when to inhale and exhale) with the tempo matched to the patient's normal breathing period. Patients tended to inhale more consistently when given instruction, as assessed by an external marker movement. This resulted in smaller variation in expiration and inspiration marker positions relative to total excursion, thereby permitting more precise gating tolerances at those parts of the breathing cycle. Breathing instruction also reduced the fraction of session times having irregular breathing as measured by the system software, thereby potentially increasing the accelerator duty factor and decreasing treatment times. Fluoroscopy studies showed external monitor movement to correlate well with that of the diaphragm in four patients, whereas time delays of up to 0.7 s in diaphragm movement were observed in two patients with impaired lung function. From fluoroscopic observations, average patient diaphragm excursion was reduced from 1.4 cm (range 0.7-2.1 cm) without gating and without breathing instruction, to 0.3 cm (range 0.2-0.5 cm) with instruction and with gating tolerances set for treatment at expiration for 25% of the breathing cycle. Patients expressed no difficulty with following instruction for the duration of a session. We conclude that the external monitor accurately predicts internal respiratory motion in most cases; however, it may be important to check with fluoroscopy for possible time delays in patients with impaired lung function. Furthermore, we observe that verbal instruction can improve breathing regularity, thus improving the performance of gated treatments with this system.

Respiratory-driven lung tumor motion is independent of tumor size, tumor location, and pulmonary function

PURPOSE

To determine whether superior-inferior lung tumor motion is predictable by tumor size or location, or pulmonary function test results.

METHODS AND MATERIALS

Superior-inferior tumor motion was measured on orthogonal radiographs taken during simulation of 22 patients with inoperable lung cancer diagnosed by orthogonal radiographs.

RESULTS

The tumor size averaged 5.5 +/- 3.1 cm (range 1.5-12 cm). Seven of 11 central tumors demonstrated some motion compared with 5 of 11 peripheral tumors. Four of 5 upper lobe tumors moved compared with 8 of 17 tumors that were either middle or lower lobe lesions. The mean fourth rib motion was 7.3 +/- 3.2 mm (range 2-15). The mean FeV(1) was 1.8 +/- 1.2 (range 0.55-5.33. The mean diffusing capacity of the lung for carbon monoxide was 14.0 +/- 6.5 (range 7.8-21.9). The mean total lung capacity was 6.5 +/- 1.2 (range 3.3-8.4). None of these parameters correlated with tumor motion. Although lateral tumor motion could not be consistently determined, 1 tumor moved 10 mm anterior-posteriorly.

CONCLUSIONS

Lung tumors often move significantly during respiration. Tumor motion is not predictable by tumor size or location, or pulmonary function test results. Therefore, tumor motion must be measured in all patients. Measurement in three dimensions will likely be necessary to maximize the irradiated lung volumes or choose beam arrangements parallel to the major axis of motion.

Fluoroscopic study of tumor motion due to breathing: facilitating precise radiation therapy for lung cancer patients

Target motion due to breathing is one of the major obstacles in dose escalation of radiation therapy to some tumors in the thoracoabdominal region. The development of beam gating or target motion tracking techniques provides a possibility to reduce normal tissue volume in a treatment field. Tumor motion monitoring in those techniques plays a crucial role, but has not yet been adequately explored. This paper reports our preliminary investigation on breath introduced tumor motion. Tumor locations and motion properties were determined from digitized fluoroscopic videos acquired during patient simulation. Image distortion due to irregularities in the imaging chain, such as the pincushion distortion, was corrected with a polynomial unwarping method. Temporal Fourier transformation of the fluoroscopic video was introduced to convert the motion information over time to a static view of a motion field, in which regions with different motion ranges can be directly measured. Patient breathing patterns vary from patient to patient and so does the kinematic behavior of individual tumors. In order to evaluate the feasibility for tracking internal target motion with nonionizing-radiation techniques, motion patterns between internal targets and external radio opaque markers placed on patient's chest during fluoroscopic video acquisition were compared. For some patients, significant motion phase discrepancies between an internal target and an external marker have been observed. Quantitative measurements are reported. These results will be useful in the design of a motion tracking or gated radiotherapy system.

Dosimetric evaluation of lung tumor immobilization using breath hold at deep inspiration

PURPOSE

To examine the dosimetric benefit of self-gated radiotherapy at deep-inspiration breath hold (DIBH) in the treatment of patients with non-small-cell lung cancer (NSCLC). The relative contributions of tumor immobilization at breath hold (BH) and increased lung volume at deep inspiration (DI) in sparing high-dose lung irradiation (> or = 20 Gy) were examined.

METHODS AND MATERIALS

Ten consecutive patients undergoing radiotherapy for Stage I-IIIB NSCLC who met the screening criteria were entered on this study. Patients were instructed to BH at DI without the use of external monitors or breath-holding devices (self-gating). Computed tomography (CT) scans of the thorax were performed during free breathing (FB) and DIBH. Fluoroscopy screened for reproducible tumor position throughout DIBH, and determined the maximum superior-inferior (SI) tumor motion during both FB and DIBH. Margins used to define the planning target volume (PTV) from the clinical target volume included 1 cm for setup error and organ motion, plus an additional SI margin for tumor motion, as determined from fluoroscopy. Three conformal treatment plans were then generated for each patient, one from the FB scan with FB PTV margins, a second from the DIBH scan with FB PTV margins, and a third from the DIBH scan with DIBH PTV margins. The percent of total lung volume receiving > or = 20 Gy (using a prescription dose of 70.9 Gy to isocenter) was determined for each plan.

RESULTS

Self-gating at DIBH was possible for 8 of the 10 patients; 2 patients were excluded, because they were not able to perform a reproducible DIBH. For these 8 patients, the median BH time was 23 (range, 19-52) s. The mean percent of total lung volume receiving > or = 20 Gy under FB conditions (FB scan with FB PTV margins) was 12.8%. With increased lung volume alone (DIBH scan with FB PTV margins), this was reduced to 11.0%, tending toward a significant decrease in lung irradiation over FB (p = 0.086). With both increased lung volume and tumor immobilization (DIBH scan with DIBH PTV margins), the mean percent lung volume receiving > or = 20 Gy was further reduced to 8.8%, a significant decrease in lung irradiation compared to FB (p = 0.011). Furthermore, at DIBH, the additional benefit provided by tumor immobilization (i.e., using DIBH instead of FB PTV margins) was also significant (p = 0.006). The relative contributions of tumor immobilization and increased lung volume toward reducing the percent total lung volume receiving > or = 20 Gy were patient specific; however, all 8 of the patients analyzed showed a dosimetric benefit with this DIBH technique.

CONCLUSION

Compared to FB conditions, at DIBH the mean reduction in percent lung volume receiving > or = 20 Gy was 14.3% with the increase in lung volume alone, 22.1% with tumor immobilization alone, and 32.5% with the combined effect. The dosimetric benefit seen at DIBH was patient specific, and due to both the increased lung volume seen at DI and the PTV margin reduction seen with tumor immobilization.

Organ motion and its management

PURPOSE

To compile and review data on the topic of organ motion and its management.

METHODS AND MATERIALS

Data were classified into three categories: (a) patient position-related organ motion, (b) interfraction organ motion, and (c) intrafraction organ motion. Data on interfraction motion of gynecological tumors, the prostate, bladder, and rectum are reviewed. Literature pertaining to the intrafraction movement of the liver, diaphragm, kidneys, pancreas, lung tumors, and prostate is compiled. Methods for managing interfraction and intrafraction organ motion in radiation therapy are also reviewed.

Technical aspects of the deep inspiration breath-hold technique in the treatment of thoracic cancer

PURPOSE

The goal of this paper is to describe our initial experience with the deep inspiration breath-hold (DIBH) technique in conformal treatment of non-small-cell lung cancer with particular emphasis on the technical aspects required for implementation.

METHODS AND MATERIALS

In the DIBH technique, the patient is verbally coached through a modified slow vital capacity maneuver and brought to a reproducible deep inspiration breath-hold level. The goal is to immobilize the tumor and to expand normal lung out of the high-dose region. A physicist or therapist monitors and records patient breathing during simulation, verification, and treatment using a spirometer with a custom computer interface. Examination of internal anatomy during fluoroscopy over multiple breath holds establishes the reproducibility of the DIBH maneuver for each patient. A reference free-breathing CT scan and DIBH planning scan are obtained. To provide an estimate of tumor motion during normal tidal breathing, additional scan sets are obtained at end inspiration and end expiration. These are also used to set the spirometer action levels for treatment. Patient lung inflation is independently verified over the course of treatment by comparing the distance from the isocenter to the diaphragm measured from the DIBH digitally reconstructed radiographs to the distance measured on the portal films. Patient breathing traces obtained during treatment were examined retrospectively to assess the reproducibility of the technique.

RESULTS

Data from the first 7 patients, encompassing over 250 treatments, were analyzed. The inferred displacement of the centroid of gross tumor volume from its position in the planning scan, as calculated from the spirometer records in over 350 breath holds was 0.02 +/- 0.14 cm (mean and standard deviation). These data are consistent with the displacements of the diaphragm (-0.1 +/- 0.4 cm; range, from -1.2 to 1.1 cm) relative to the isocenter, as measured on the (92) portal films. The latter measurements include the patient setup error. The patient averaged displacement of the tumor during free breathing, determined from the tumor displacement between end inspiration and end expiration, was 0.8 +/- 0.5 cm in both the superior-inferior and anterior-posterior directions and 0.1 cm (+/- 0.1 cm) medial-laterally.

CONCLUSION

Treatment of patients with the DIBH technique is feasible in a clinical setting. With this technique, consistent lung inflation levels are achieved in patients, as judged by both spirometry and verification films. Breathing-induced tumor motion is significantly reduced using DIBH compared to free breathing, enabling better target coverage.