Stereotactic high dose fraction radiation therapy of extracranial tumors using an accelerator. Clinical experience of the first thirty-one patients

Extracranial stereotactic radiotherapy for primary and metastatic renal cell carcinoma

BACKGROUND AND PURPOSE

We investigated the results of using stereotactic radiotherapy (SRT) for 58 patients with renal cell carcinomas (RCC) who were evaluated restrospectively for response rates, local control rates and side effects.

PATIENTS AND METHODS

From October 1997 to January 2003, 50 patients suffering from metastatic RCC and eight patients with inoperable primary RCC received high-dose fraction SRT while placed in a stereotactic body-frame. The most common dose/fractionation schedules used were 8 Gyx4, 10 Gyx4 and 15 Gyx3 during approximately 1 week.

RESULTS

SRT-treated tumor lesions regressed totally in 30% of the patients at 3-36 months, whereas 60% of the patients had a partial volume reduction or no change after a median follow-up of 37 months (SD 17.4) for censored and 13 months (SD 12.9) for uncensored patients. Side effects were generally mild. Of 162 treated tumors, only three recurred, yielding a local control rate of 90-98%, considering the 8% non-evaluable sites as defined here. For patients with one to three metastases, the time to new spread was 9 months.

CONCLUSIONS

Our use of SRT for patients with primary and metastatic RCC yielded a high local control rate with low toxicity. Patients with one to three metastases, local recurrences after nephrectomy or inoperable primary tumors benefited the most, i.e. had fewer distant recurrences (13/23) and longer survival times compared to patients with >3 metastases (24/27 recurrences).

Stereotaktische Strahlentherapie von Lebermetastasen

Advances in radiation oncology made possible the locally curative treatment approach of stereotactically guided radiation therapy of liver tumours. Results of this highly focussed therapy were published by only a few centres. The radiation dose is delivered in one or a few fractions with high single doses. All published results show high local tumour control with low treatment morbidity. The treatment results of this noninvasive technique are similar to those of minimally invasive ablative therapies. Our own and other published data are summarized and discussed. The long-term results of this technique are currently being evaluated in a prospective multicentre trial.

Impact of IMRT and leaf width on stereotactic body radiotherapy of liver and lung lesions

PURPOSE

The present study explored the impact of intensity-modulated radiotherapy (IMRT) on stereotactic body RT (SBRT) of liver and lung lesions. Additionally, because target dose conformity can be affected by the leaf width of a multileaf collimator (MLC), especially for small targets and stereotactic applications, the use of a micro-MLC on "uniform intensity" conformal and intensity-modulated SBRT was evaluated.

METHODS AND MATERIALS

The present study included 10 patients treated previously with SBRT in our institution (seven lung and three liver lesions). All patients were treated with 3 x 12 Gy prescribed to the 65% isodose level. The actual MLC-based conformal treatment plan served as the standard for additional comparison. In total, seven alternative treatment plans were made for each patient: a standard (actual) plan and an IMRT plan, both calculated with Helax TMS (Nucletron) using a pencil beam model; and a recalculated standard and a recalculated IMRT plan on Helax TMS using a point dose kernel approach. These four treatment plans were based on a standard MLC with 1-cm leaf width. Additionally, the following micro-MLC (central leaf width 3 mm)-based treatment plans were calculated with the BrainSCAN (BrainLAB) system: standard, IMRT, and dynamic arc treatments. For each treatment plan, various target parameters (conformity, coverage, mean, maximal, and minimal target dose, equivalent uniform doses, and dose-volume histogram), as well as organs at risk parameters (3 Gy and 6 Gy volume, mean dose, dose-volume histogram) were evaluated. Finally, treatment efficiency was estimated from monitor units and the number of segments for IMRT solutions.

RESULTS

For both treatment planning systems, no significant difference could be observed in terms of target conformity between the standard and IMRT dose distributions. All dose distributions obtained with the micro-MLC showed significantly better conformity values compared with the standard and IMRT plans using a regular MLC. Dynamic arc plans were characterized by the steepest dose gradient and thus the smallest V(6 Gy) values, which were on average 7% smaller than the standard plans and 20% lower than the IMRT plans. Although the Helax TMS IMRT plans show about 18% more monitor units than the standard plan, BrainSCAN IMRT plans require approximately twice the number of monitor units relative to the standard plan. All treatment plans optimized with a pencil beam model but recalculated with a superposition method showed significant qualitative, as well as quantitative, differences, especially with respect to conformity and the dose to organs at risk.

CONCLUSION

Standard conformal treatment techniques for SBRT could not be improved with inversely planned IMRT approaches. Dose calculation algorithms applied in optimization modules for IMRT applications in the thoracic region need to be based on the most accurate dose calculation algorithms, especially when using higher energy photon beams.

Multifractionated image-guided and stereotactic intensity-modulated radiotherapy of paraspinal tumors: A preliminary report

PURPOSE

The use of image-guided and stereotactic intensity-modulated radiotherapy (IMRT) techniques have made the delivery of high-dose radiation to lesions within close proximity to the spinal cord feasible. This report presents clinical and physical data regarding the use of IMRT coupled with noninvasive body frames (stereotactic and image-guided) for multifractionated radiotherapy.

METHODS AND MATERIALS

The Memorial Sloan-Kettering Cancer Center (Memorial) stereotactic body frame (MSBF) and Memorial body cradle (MBC) have been developed as noninvasive immobilizing devices for paraspinal IMRT using stereotactic (MSBF) and image-guided (MBC) techniques. Patients were either previously irradiated or prescribed doses beyond spinal cord tolerance (54 Gy in standard fractionation) and had unresectable gross disease involving the spinal canal. The planning target volume (PTV) was the gross tumor volume with a 1 cm margin. The PTV was not allowed to include the spinal cord contour. All treatment planning was performed using software developed within the institution. Isocenter verification was performed with an in-room computed tomography scan (MSBF) or electronic portal imaging devices, or both. Patients were followed up with serial magnetic resonance imaging every 3-4 months, and no patients were lost to follow-up. Kaplan-Meier statistics were used for analysis of clinical data.

RESULTS

Both the MSBF and MBC were able to provide setup accuracy within 2 mm. With a median follow-up of 11 months, 35 patients (14 primary and 21 secondary malignancies) underwent treatment. The median dose previously received was 3000 cGy in 10 fractions. The median dose prescribed for these patients was 2000 cGy/5 fractions (2000-3000 cGy), which provided a median PTV V100 of 88%. In previously unirradiated patients, the median prescribed dose was 7000 cGy (5940-7000 cGy) with a median PTV V100 of 90%. The median Dmax to the cord was 34% and 68% for previously irradiated and never irradiated patients, respectively. More than 90% of patients experienced palliation from pain, weakness, or paresthesia; 75% and 81% of secondary and primary lesions, respectively, exhibited local control at the time of last follow-up. No cases of radiation-induced myelopathy or radiculopathy have thus far been encountered.

CONCLUSIONS

Precision stereotactic and image-guided paraspinal IMRT allows the delivery of high doses of radiation in multiple fractions to tumors within close proximity to the spinal cord while respecting cord tolerance. Although preliminary, the clinical results are encouraging.

Stereotactic hypofractionated radiation therapy for stage I non-small cell lung cancer

We reviewed our initial institutional experience with the use of stereotactic hypofractionated radiation therapy (SFRT) in patients with stage I non-small cell lung cancer (NSCLC). Thirty patients with inoperable stage I non-small cell lung cancer due to a severe chronic obstructive pulmonary disease (COPD) and/or chronic heart disease (Eastern Cooperative Oncology Group (ECOG) performance status of 0-2) were treated between December 2000 and October 2003 with SFRT in curative intent. Infiltration of locoregional lymph nodes and distant metastases were ruled out by computerized tomography (CT) scan of the brain, thorax, and abdomen, and by whole body FDG-positron emission tomography scan in all patients. Total RT doses ranged from 24.0 to 37.5 Gy, given in 3-5 fractions to the 60% isodose encompassing the planning target volume. Immobilization was carried out by a vacuum couch and a low-pressure foil. The clinical target volume was the tumor as it appeared in lung windowing on lung CT scan. Organ movements (caused by breathing; range, 6-22 mm) and reproducibility of patient positioning in the couch (range, 3-12 mm) were calculated by sequential CT and orthogonal films. The individual values were taken into account as a safety margin for the definition of the planning target volume (PTV). The median follow-up of living patients is 18 months (range, 6-38 months). As maximum response, there were 10 (33%) complete responses (CRs) and 14 (47%) partial responses (PRs), resulting in a total response rate of 80%. Stable disease was observed in 6 (20%) patients, while no patient experienced progressive disease. During follow-up, 2 (7%) local recurrences were observed (after 17 and 18 months, respectively). Of 5 (17%) patients who developed distant metastasis, 1 patient developed it in liver (3 months), another one in brain (6 months), and another one in the lung (36 months), while 2 patients developed it in mediastinal lymph nodes (after 8, and 11 months, respectively) only. Of 9 (30%) patients who have died, only 3 (10%) died of cancer, while 6 (20%) died of cancer-unrelated or unknown causes. Acute side effects were mild and affected 9 (33%) patients during the RT course (fatigue being the most frequent one in 6 patients). There were 22 acute events occurring in 19 (63%) patients during the first 3 months post-SFRT, the most frequent one being pneumonitis observed in 14 (46%) patients. However, there was only one (3%) grade 3 acute toxicity and no patient experienced greater than grade 3 toxicity during this study. One (3%) patient experienced rib fracture as the late event. SFRT is a feasible and safe treatment method in inoperable patients with stage I NSCLC having reduced lung capacity. Longer follow-up is necessary to get robust data on late toxicity as well as survival.

Treatment planning of stereotactic radiotherapy for solitary lung tumor

PURPOSE

To analyze the stereotactic radiotherapy (SRT) plans in terms of internal target volume (ITV) and organs at risk (OARs).

METHODS AND MATERIALS

Treatment planning and dose distributions were analyzed using dose-volume histograms (DVHs) of ITV and OARs in 37 patients, who were treated for a solitary lung tumor with SRT. The stereotactic body frame (SBF) was used for immobilization and accurate setup. Prescription dose was 48 Gy in four fractions at the isocenter.

RESULTS

Use of SBF limits the extent of the noncoplanar beam directions to prevent a collision with the Linac gantry. DVH analyses showed that the homogeneity index, defined as the ratio of maximum and minimum dose to ITV, ranged from 1.03 to 1.25 (mean, 1.12). The volume irradiated with 20 Gy or more (V(20)) of the lung ranged from 0.3 to 11.6% (mean, 4.4%) of the whole lung volume. The maximum dose to the other OARs ranged from 0 to 11.8 Gy (mean, 0.5-2.7) per fraction. No clinically significant complications were encountered.

CONCLUSIONS

Despite the limitation of the beam arrangement, a homogeneous target dose distribution, while avoiding high doses to normal tissues, was obtained.

Nonsurgical Therapy for Stages I and II Non–Small Cell Lung Cancer

For patients who have stages I and II non-small cell lung cancer (NSCLC) and who are unable or unwilling to undergo surgical resection, nonsurgical treatment modalities have been used with curative intent. Conventionally fractionated radiotherapy has been the mainstay of nonsurgical therapy; however, advances in technology and the clinical application of radiobiologic principles have allowed more accurately targeted treatment that delivers higher effective doses to the tumor, while respecting the tolerance of surrounding normal tissues. This article discusses nonsurgical approaches to the treatment of early-stage NSCLC, including several promising techniques, such as radiation dose escalation, altered radiation fractionation, stereotactic radiotherapy, and radiofrequency ablation.

Hypofractionation in non-small cell lung cancer (NSCLC): suggestions from modelling both acute and chronic hypoxia

Based on experimental estimates for acute and chronic tumour hypoxia, a speculative analysis of the therapeutic ratio dependence on the number of once-daily five-days-per-week fractions (n) for non-small cell lung cancer (NSCLC) radiotherapy is proposed. For this purpose an adapted formulation of the linear-quadratic model has been derived, including the effects of tumour repopulation, inter-tumour alpha-heterogeneity and oxygen enhancement ratio dependence on the dose per fraction. The relation between the curative dose D50, assuring 50% tumour control probability, and n has been computed: for (n, D50) fractionation schemes, the therapeutic ratios have been compared in terms of effective normalized total doses to the lungs (NTD(eff)L), estimated by a few supposed fractions of the normalized total dose to the tumour. Results suggest that D50 is dominated by chronic hypoxia for shortly hypofractionated treatments and by acute hypoxia for multifractionated treatments. Furthermore, the optimum number of fractions depends on the rapidity of the reoxygenation from chronically hypoxic cells, almost independently of the extent of both chronic and acute hypoxia. For NSCLC, both the reduction of n until about 20 fractions in hypofractionated dose-escalation trials, and the extension of extra-cranial stereotactic radiotherapy schedules to include at least 5-10 fractions, seem to be supported by this model.

Four-dimensional radiotherapy planning for DMLC-based respiratory motion tracking

Four-dimensional (4D) radiotherapy is the explicit inclusion of the temporal changes in anatomy during the imaging, planning, and delivery of radiotherapy. Temporal anatomic changes can occur for many reasons, though the focus of the current investigation is respiration motion for lung tumors. The aim of this study was to develop 4D radiotherapy treatment-planning methodology for DMLC-based respiratory motion tracking. A 4D computed tomography (CT) scan consisting of a series of eight 3D CT image sets acquired at different respiratory phases was used for treatment planning. Deformable image registration was performed to map each CT set from the peak-inhale respiration phase to the CT image sets corresponding to subsequent respiration phases. Deformable registration allows the contours defined on the peak-inhale CT to be automatically transferred to the other respiratory phase CT image sets. Treatment planning was simultaneously performed on each of the eight 3D image sets via automated scripts in which the MLC-defined beam aperture conforms to the PTV (which in this case equaled the GTV due to CT scan length limitations) plus a penumbral margin at each respiratory phase. The dose distribution from each respiratory phase CT image set was mapped back to the peak-inhale CT image set for analysis. The treatment intent of 4D planning is that the radiation beam defined by the DMLC tracks the respiration-induced target motion based on a feedback loop including the respiration signal to a real-time MLC controller. Deformation with respiration was observed for the lung tumor and normal tissues. This deformation was verified by examining the mapping of high contrast objects, such as the lungs and cord, between image sets. For the test case, dosimetric reductions for the cord, heart, and lungs were found for 4D planning compared with 3D planning. 4D radiotherapy planning for DMLC-based respiratory motion tracking is feasible and may offer tumor dose escalation and/or a reduction in treatment-related complications. However, 4D planning requires new planning tools, such as deformable registration and automated treatment planning on multiple CT image sets.

Toxicity and outcome results of RTOG 9311: a phase I-II dose-escalation study using three-dimensional conformal radiotherapy in patients with inoperable non-small-cell lung carcinoma

PURPOSE

To evaluate prospectively the acute and late morbidities from a multiinstitutional three-dimensional radiotherapy dose-escalation study for inoperable non-small-cell lung cancer.

METHODS AND MATERIALS

A total of 179 patients were enrolled in a Phase I-II three-dimensional radiotherapy dose-escalation trial. Of the 179 patients, 177 were eligible. The use of concurrent chemotherapy was not allowed. Twenty-five patients received neoadjuvant chemotherapy. Patients were stratified at escalating radiation dose levels depending on the percentage of the total lung volume that received >20 Gy with the treatment plan (V(20)). Patients with a V(20) <25% (Group 1) received 70.9 Gy in 33 fractions, 77.4 Gy in 36 fractions, 83.8 Gy in 39 fractions, and 90.3 Gy in 42 fractions, successively. Patients with a V(20) of 25-36% (Group 2) received doses of 70.9 Gy and 77.4 Gy, successively. The treatment arm for patients with a V(20) > or =37% (Group 3) closed early secondary to poor accrual (2 patients) and the perception of excessive risk for the development of pneumonitis. Toxicities occurring or persisting beyond 90 days after the start of radiotherapy were scored as late toxicities. The estimated toxicity rates were calculated on the basis of the cumulative incidence method.

RESULTS

The following acute Grade 3 or worse toxicities were observed for Group 1: 70.9 Gy (1 case of weight loss), 77.4 Gy (nausea and hematologic toxicity in 1 case each), 83.8 Gy (1 case of hematologic toxicity), and 90.3 Gy (3 cases of lung toxicity). The following acute Grade 3 or worse toxicities were observed for Group 2: none at 70.9 Gy and 2 cases of lung toxicity at 77.4 Gy. No patients developed acute Grade 3 or worse esophageal toxicity. The estimated rate of Grade 3 or worse late lung toxicity at 18 months was 7%, 16%, 0%, and 13% for Group 1 patients receiving 70.9, 77.4, 83.8, or 90.3 Gy, respectively. Group 2 patients had an estimated late lung toxicity rate of 15% at 18 months for both 70.9 and 77.4 Gy. The prognostic factors for late pneumonitis in multivariate analysis were the mean lung dose and V(20). The estimated rate of late Grade 3 or worse esophageal toxicity at 18 months was 8%, 0%, 4%, and 6%, for Group 1 patients receiving 70.9, 77.4, 83.8, 90.3 Gy, respectively, and 0% and 5%, respectively, for Group 2 patients receiving 70.9 and 77.4 Gy. The dyspnea index scoring at baseline and after therapy for functional impairment, magnitude of task, and magnitude of effort revealed no change in 63%, functional pulmonary loss in 23%, and pulmonary improvement in 14% of patients. The observed locoregional control and overall survival rates were each similar among the study arms within each dose level of Groups 1 and 2. Locoregional control was achieved in 50-78% of patients. Thirty-one patients developed regional nodal failure. The location of nodal failure in relationship to the RT volume was documented in 28 of these 31 patients. Twelve patients had isolated elective nodal failures. Fourteen patients had regional failure in irradiated nodal volumes. Two patients had both elective nodal and irradiated nodal failure.

CONCLUSIONS

The radiation dose was safely escalated using three-dimensional conformal techniques to 83.8 Gy for patients with V(20) values of <25% (Group 1) and to 77.4 Gy for patients with V(20) values between 25% and 36% (Group 2), using fraction sizes of 2.15 Gy. The 90.3-Gy dose level was too toxic, resulting in dose-related deaths in 2 patients. Elective nodal failure occurred in <10% of patients.

Treatment of locally advanced non-small cell lung cancer in the elderly

PURPOSE OF REVIEW

Non-small cell lung cancer (NSCLC) may be considered typical of advanced age. Most cases of NSCLC are diagnosed in the advanced or locally advanced stage. It has been shown that combined chemo-radiotherapy is more efficient than either chemotherapy alone or radiation alone, for the therapeutic management of localized unresectable NSCLC. However, chemo-radiotherapy, even if given with sequential approach, in clinical practice can be contraindicated in elderly patients. In fact, this patient population often present at diagnosis with cardiovascular and/or pulmonary comorbidities that increase the risk of severe side effects from chemo-radiotherapy. The present review aims at focusing the currently available evidences on the treatment of elderly patients affected by locally advanced NSCLC and at giving future perspectives on this topic.

RECENT FINDINGS

Very few specific prospective data are available on the treatment of locally advanced NSCLC in the elderly. Some phase II studies suggest that low-dose chemotherapy given concurrently with radiotherapy could be safely administered to this patient population. Retrospective analyses on full-dose sequential and concurrent chemo-radiation are to be considered globally ambiguous and at risk of selection bias.

SUMMARY

Only specifically designed prospective studies will elucidate the real role and feasibility of combined chemo-radiotherapy in the treatment of locally advanced NSCLC in the elderly. Future perspectives on this topic include the evaluation of alternative schedules of chemo-radiotherapy, innovative radiation techniques more suitable to elderly patients, and the introduction of new, well-tolerated, molecularly targeted agents combined with standard treatments.

How can we further improve radiotherapy for stage-III non-small-cell lung cancer?

Combined modality treatment in advanced NSCLC has produced some gain in treatment outcome. Local control as addressed by radiotherapy is still a significant site of failure. Doses higher than achieved by conventional conformal radiotherapy are shown to result in better control rates. Volume restriction seems to be the most important issue in dose escalation. Integration of PET imaging into target definition, omission of clinically uninvolved lymph-node areas and measures to decrease set-up and movement uncertainties are explored. Introduction of risk estimation based on dose-volume analysis for dose prescription may further optimise individual treatment.

A challenge to traditional radiation oncology

PURPOSE

To investigate and compare the biologically effective doses, equivalent doses in 2-Gy fractions, log tumor cells killed, and late effects that can be estimated for the large fractions in short overall times that are now being delivered in various clinically used schedules in several countries for the treatment of cancer in human lungs, liver, and kidney.

METHODS AND MATERIALS

Linear quadratic (LQ) modeling is employed with only the standard assumptions that tumor alpha/beta ratio is 10 Gy, pneumonitis and late complication alpha/beta ratios are 3 Gy, that intrinsic radiosensitivity of tumor cells is 0.35 ln/Gy, that no tumor repopulation occurs within 2 weeks, and that LQ modeling is valid up to 23 Gy per fraction. As well as the planning target volume (PTV), we propose a practical term called the prescription isodose volume (PIV) to be used in this discussion. In the ideal case of 100% conformity, PIV equals PTV, but usually PIV is larger than the PTV. Biologically effective doses (BED) in Gy(10) for tumors or Gy(3) for normal lung are calculated and converted to equivalent doses in 2 Gy fractions (= normalized total doses [NTD]), and to estimated log cell kill. How such large biologic doses might be delivered to tissues is discussed.

RESULTS

Tumor cell kill varies between 16 and 27 logs to base 10 for schedules from 4F x 12 Gy to 3F x 23 Gy. The rationale for the high end of this scale is the possible presence of hypoxic or otherwise extraordinarily resistant cells, but how many tumors and which ones require such doses is not known. How can such large doses be tolerated? In "parallel type organs," it is shown to be theoretically possible, provided that suitably small volumes are irradiated, with rapid fall-off of dose outside the PTV, and a mean dose (excluding PTV and allowing for local fraction size) to both lungs of less than 19 Gy NTD. If suitably small PTVs were used, local late BEDs have been given which were as large as 600 Gy(3), equivalent to 2 Gy x 180F = 360 Gy in 2-Gy fractions, with remarkably few complications reported clinically. Questions of concurrent chemotherapy and microscopic extension of lung tumor cells are discussed briefly.

CONCLUSIONS

Such large doses can apparently be given, with suitable precautions and experience. Ongoing clinical trials from an increasing number of centers will be reporting the results of tumor control and complications from this new modality of biologically higher doses.

External beam radiation therapy for hepatocellular carcinoma: potential of intensity-modulated and image-guided radiation therapy

External beam radiotherapy has historically played a minor role in the primary treatment of hepatocellular carcinoma. Although there is evidence for tumor response to external beam radiotherapy and despite the fact that a radiation dose-response relationship has been established, the limited radiation tolerance of the adjacent normal liver has prohibited wider use of radiation therapy in this disease. Recent technological and conceptual developments in the field of radiation therapy-such as intensity-modulated radiation therapy, image-guided radiation therapy, and stereotactic body radiation therapy-have the potential to improve radiation treatments by conforming the delivered radiation dose distribution tightly to the tumor or target volume outline while sparing normal liver tissue from high-dose radiation. Image guidance allows for a reduction of added (normal tissue) safety margins designed to account for interfraction patient and target setup variability, and stereotactic targeting will further reduce residual target setup uncertainty. Combining improvements in tumor targeting with normal tissue sparing, radiation dose delivery will enable clinically effective and safe radiation delivery for liver tumors such as hepatocellular carcinoma. This article reviews the role of radiotherapy for hepatocellular carcinoma; presents modern radiation therapy modalities and concepts such as intensity-modulated, image-guided, and stereotactic body radiation therapy; and hypothesizes about their future effect on primary treatment alternatives.

Stereotactic radiotherapy for primary lung cancer and pulmonary metastases: a noninvasive treatment approach in medically inoperable patients

PURPOSE

The clinical results of dose escalation using stereotactic radiotherapy to increase local tumor control in medically inoperable patients with Stage I-II non-small-cell lung cancer or pulmonary metastases were evaluated.

METHODS AND MATERIALS

Twenty patients with Stage I-II non-small-cell lung cancer and 41 patients with 51 pulmonary metastases not amenable to surgery were treated with stereotactic radiotherapy at 3 x 10 Gy (n = 19), 3 x 12-12.5 Gy to the planning target volume enclosing 100%-isodose, with normalization to 150% at the isocenter; n = 26) or 1 x 26 Gy to the planning target volume enclosing 80%-isodose (n = 26). The median follow-up was 11 months (range, 2-61 months) for primary lung cancer patients and 9 months (range, 2-37 months) for patients with metastases.

RESULTS

The actuarial local control rate was 92% for lung cancer patients and 80% for metastasis patients > or =1 year after treatment and was significantly improved by increasing the dose from 3 x 10 Gy to 3 x 12-12.5 Gy or 1 x 26 Gy (p = 0.038). The overall survival rate after 1 and 2 years was 52% and 32%, respectively, for lung cancer patients and 85% and 33%, respectively, for metastasis patients, impaired because of systemic disease progression. After 12 months, 60% of patients with primary lung cancer and 35% of patients with pulmonary metastases were without systemic progression. No severe acute or late toxicity was observed, and only 2 patients (3%) developed symptomatic Grade 2 pneumonitis, which was successfully treated with oral steroids.

CONCLUSION

Stereotactic radiotherapy for lung tumors offers a very effective treatment option locally without significant complications in medically impaired patients who are not amenable to surgery. Patient selection is important, because those with a low risk of systemic progression are more likely to benefit from this approach.

The role of radiotherapy in the treatment of liver metastases

Radiotherapy has historically played a minor role in the treatment of patients with unresectable liver metastases from colorectal cancer and other malignancies. This can be attributed chiefly to the low tolerance of the whole liver to radiation. High-precision radiotherapy planning techniques have allowed much higher doses of radiation to be delivered safely to focal liver metastases, while sparing most of the normal liver. When combined with hepatic arterial fluorodeoxyuridine, high-dose focal liver radiotherapy is associated with excellent response rates, local control, and survival in patients with unresectable liver metastases from colorectal cancer. Radiotherapy, with and without concurrent systemic chemotherapy, has also been used with encouraging outcomes for patients with liver metastases from colorectal cancer and other cancers. There appears to be a radiation dose response for liver metastases; tumors treated with doses of 70 Gy or greater are likelier to have durable local control. Advancements in tumor imaging, in radiotherapy techniques that will allow the safe delivery of higher doses of radiation, and in novel tumor radiation sensitizers and normal tissue radioprotectors should substantially improve the outcome of patients with unresectable liver metastases treated with radiotherapy.

Daily ultrasound-based image-guided targeting for radiotherapy of upper abdominal malignancies

PURPOSE

Development and implementation of a strategy to use a stereotactic ultrasound (US)-based image-guided targeting device (BAT) to align intensity-modulated radiotherapy (IMRT) target volumes accurately in the upper abdomen. Because the outlines of such targets may be poorly visualized by US, we present a method that uses adjacent vascular guidance structures as surrogates for the target position. We assessed the potential for improvement of daily repositioning and the feasibility of daily application.

METHODS AND MATERIALS

A total of 62 patients were treated by sequential tomotherapeutic IMRT between October 2000 and June 2003 for cholangiocarcinoma and gallbladder carcinoma (n = 10), hepatocellular carcinoma (n = 10), liver metastases (n = 11), pancreatic carcinoma (n = 20), neuroblastoma (n = 3), and other abdominal and retroperitoneal tumors (n = 8). The target volumes (TVs) and organs at risk were delineated in contrast-enhanced CT data sets. Additionally, vascular guidance structures in close anatomic relation to the TV, or within the TV, were delineated. Throughout the course of IMRT, US BAT images were acquired during daily treatment positioning. In addition to the anatomic structures typically used for US targeting (e.g., the TV and dose-limiting organs at risk), CT contours of guidance structures were superimposed onto the real-time acquired axial and sagittal US images, and target position adjustments, as indicated by the system, were performed accordingly. We report the BAT-derived distribution of shifts in the three principal room axes compared with a skin-mark-based setup, as well as the time required to perform BAT alignment. The capability of the presented method to improve target alignment was assessed in 15 patients by comparing the organ and fiducial position between the respective treatment simulation CT with a control CT study after US targeting in the CT suite.

RESULTS

A total of 1,337 BAT alignments were attempted. US images were not useful in 56 setups (4.2%), mainly because of limited visibility due to daily variations in colonic and gastric air. US imaging was facilitated in intrahepatic tumors and asthenic patients. The mean +/- SD shift from the skin mark position was 4.9 +/- 4.35, 6.0 +/- 5.31, and 6.0 +/- 6.7 mm in the x, y, and z direction, respectively. The mean magnitude vector of three-dimensional alignment correction was 11.4 +/- 7.6 mm. The proportion of daily alignments corrected by a magnitude of >10, >15, and >20 mm was 48.9%, 25.1%, and 12.7%, respectively. The magnitude of shifts in the principal directions, as well as the three-dimensional vector of displacement, was statistically significant (test against the zero hypothesis) at p <0.0001. The guidance structures that were the most valuable for identification of the TV position were the branches of the portal vein, hepatic artery, and dilated bile ducts in intrahepatic lesions and the aorta, celiac trunk, superior mesenteric artery, and extrahepatic aspects of the portal vein system in retroperitoneal and extrahepatic lesions. The mean total setup time was 4.6 min. The correlation of BAT targeting with target setup error assessment in the control CT scans in 15 patients revealed setup error reduction in 14 of 15 alignments. The average setup error reduction, assessed as a reduction in the length of setup error three-dimensional magnitude vector, was 54.4% +/- 26.9%, with an observed mean magnitude of residual setup error of 4.6 +/- 3.4 mm. The sole worsening of an initial setup was by a magnitude of <2 mm. US targeting resulted in statistically significant improvements in patient setup (p = 0.03).

CONCLUSION

Daily US-guided BAT targeting for patients with upper abdominal tumors was feasible in the vast majority of attempted setups. This method of US-based image-guided tumor targeting has been successfully implemented in clinical routine. The observed improved daily repositioning accuracy might allow for individualized reduction of safety margins and optional dose escalation. Compared with the established application of the BAT device for prostate radiotherapy, in which the target can be directly visualized, the TV in the present study was predominantly positioned relative to guidance vascular structures in close anatomic relation. We perceived an enormous potential in improved and individualized patient positioning for fractionated radiotherapy and also for stereotactic extracranial radiotherapy and radiosurgery, especially for tumors of the liver and pancreas.

Stereotactic body radiation therapy: an ablative treatment option for primary and secondary liver tumors

Only a subset of patients with primary and secondary liver tumors are eligible for surgical resection because of either the presence of extrahepatic disease, increased number of hepatic lesions, the anatomical distribution of tumors within the liver, and/or general medical inoperability. Nonsurgical, ablative tumor treatment may benefit selected patients by preserving normal liver function. This review presents the concept and technology of stereotactic body radiation therapy and summarizes available clinical data describing applications in the treatment of malignant liver tumors. We present predominantly peer-reviewed data but also summarize recent clinical developments along with discussions of current ongoing and planned multicenter studies.

Advanced radiation treatment planning and delivery approaches for treatment of lung cancer

Great technologic progress has been made in the last decade in the radiation treatment of lung cancer. In particular, the widespread use of 3D conformal therapy has the potential to escalate the dose to the tumor while sparing dose to normal tissue. Current technology, however, has yet to impact local control and survival. It could be hypothesized that this is due to geographic misses because of poor target definition, movement of the tumor due to respiration, and dose/ fractionation levels. Several emerging technologies that are described in this article have the potential to address these problems, with results expected in the near future. The technical delivery of radiation has not reached its limit.

Stereotactic boost irradiation for targets in the abdomen and pelvis

Based on the experience of stereotactic irradiation of lung and liver tumors the feasibility of stereotactic boost irradiation to abdominal and pelvic tumors was evaluated. Twenty-one patients with inoperable tumors received a stereotactic boost of 2-3 x 5Gy/PTV-enclosing-100% isodose with normalization to 150% at the isocenter after normofractionated irradiation of 45-50.4Gy. Actuarial local control (16/21 targets) was 96/70% after 12 and 24 months. Treatment was feasible and well tolerated.

Stereotactic hypofractionated high-dose irradiation for stage I nonsmall cell lung carcinoma

BACKGROUND

Stereotactic irradiation (STI) has been actively performed using various methods to achieve better local control of Stage I nonsmall cell lung carcinoma (NSCLC) in Japan. The authors retrospectively evaluated results from a Japanese multiinstitutional study.

METHODS

Patients with Stage I NSCLC (n = 245; median age, 76 years; T1N0M0, n = 155; T2N0M0, n = 90) were treated with hypofractionated high-dose STI in 13 institutions. Stereotactic three-dimensional treatment was performed using noncoplanar dynamic arcs or multiple static ports. A total dose of 18-75 gray (Gy) at the isocenter was administered in 1-22 fractions. The median calculated biologic effective dose (BED) was 108 Gy (range, 57-180 Gy).

RESULTS

During follow-up (median, 24 months; range, 7-78 months), pulmonary complications of National Cancer Institute-Common Toxicity Criteria Grade > 2 were observed in only 6 patients (2.4%). Local progression occurred in 33 patients (14.5%), and the local recurrence rate was 8.1% for BED > or = 100 Gy compared with 26.4% for < 100 Gy (P < 0.05). The 3-year overall survival rate of medically operable patients was 88.4% for BED > or = 100 Gy compared with 69.4% for < 100 Gy (P < 0.05).

CONCLUSIONS

Hypofractionated high-dose STI with BED < 150 Gy was feasible and beneficial for curative treatment of patients with Stage I NSCLC. For all treatment methods and schedules, local control and survival rates were better with BED > or = 100 Gy compared with < 100 Gy. Survival rates in selected patients (medically operable, BED > or = 100 Gy) were excellent, and were potentially comparable to those of surgery.

Evaluation of Lung Injury after Three-dimensional Conformal Stereotactic Radiation Therapy for Solitary Lung Tumors: CT Appearance

PURPOSE

To evaluate the computed tomographic (CT) appearance of tumors and lung injury in patients who have undergone stereotactic radiation therapy (SRT) for solitary lung tumors.

MATERIALS AND METHODS

Twenty-seven patients with primary lung cancer and four with metastatic lung cancer who underwent SRT for solitary lung tumors were enrolled for evaluation. SRT was delivered by using a three-dimensional conformal technique with a stereotactic body frame. A total dose of 48 Gy was administered in four fractions during a period of 2 weeks. After SRT, follow-up CT images were obtained every 2-3 months. Radiation-induced pulmonary injuries were classified into four patterns on CT images. The minimal lung dose to areas demonstrating pulmonary injury at CT was evaluated, and the correlation between the dose and the percentage volume of the whole lung irradiated by more than 20 Gy in total (V20) was assessed by using Spearman rank correlation.

RESULTS

Tumor shrinkage continued for 2-15 months after SRT. Asymptomatic changes in the irradiated lung were noted at CT in all patients within 2-6 months (median, 4 months) after SRT. As the pattern at pulmonary CT changed, patchy consolidation was more predominantly seen as an acute change than were slight homogeneous increase in opacity, discrete consolidation, or solid consolidation; solid consolidation was the more predominantly seen late change. The minimal lung dose to the area demonstrating pulmonary injury in each patient ranged between 16 and 36 Gy (median, 24 Gy). The dose was significantly (P <.001) inversely correlated with the V20 in each patient.

CONCLUSION

The reaction to SRT of the lungs seems similar to the reaction to conventional radiation therapy.

Conformal chemoradiation for primary and metastatic liver malignancies

Historically, radiation therapy has played a minor role in the management of patients with unresectable primary hepatobiliary malignancies and liver metastases from colorectal cancer. This can be attributed chiefly to the low tolerance of the whole liver to radiation. Three-dimensional radiation planning techniques have allowed much higher doses of radiation to be delivered to focal liver tumors, while sparing the majority of the normal liver. When combined with fluorodeoxyuridine (FUdR), high-dose focal liver radiation is associated with excellent response rates, local control, and survival in patients with large unresectable tumors. There appears to be a radiation dose response for intrahepatic malignancies. Advancements in tumor imaging, radiation techniques that can safely deliver higher doses of radiation, novel tumor radiation sensitizers, and normal-tissue radioprotectors should substantially improve the outcome of patients with unresectable intrahepatic malignancies treated with chemoradiation.

Extracranial Stereotactic Radioablation *

INTRODUCTION

Surgical resection is standard therapy for patients with stage I non-small cell lung cancer (NSCLC), however, many patients are medically inoperable. We set out to investigate a new therapy akin to brain radiosurgery called extracranial stereotactic radioablation (ESR) in a phase I trial.

PATIENTS AND METHODS

Eligible patients included those with clinically staged T1 or T2 (tumor size, < or = 7 cm) N0M0 biopsy confirmed NSCLC. All patients had comorbid medical problems that precluded thoracotomy. The median age was 75 years, and the median Karnofsky performance status was 80. ESR was administered in three separate fractions over 2 weeks. Three to five patients were treated within each dose cohort starting at 800 cGy per fraction (total, 2,400 cGy) followed by successive dose escalations of 200 cGy per fraction (total increase per cohort, 600 cGy). Waiting periods occurred between dose cohorts to observe toxicity. Patients with T1 vs T2 tumors underwent separate independent dose escalations.

RESULTS

A total of 37 patients were enrolled since February 2000. One patient experienced grade 3 pneumonitis, and another patient had grade 3 hypoxia. For the entire population, there was no appreciable decline in cardiopulmonary function as measured by symptoms, physical examination, need for oxygen supplementation, pulmonary function testing, arterial blood gas determinations, or regular chest imaging. Both T-stage groups ultimately reached and tolerated 2,000 cGy per fraction for three fractions (total, 6,000 cGy). The maximum tolerated dose for this therapy in either T-stage group has yet to be reached. Tumors responded to treatment in 87% of patients (complete response, 27%). After a median follow-up period of 15.2 months, six patients experienced local failure, all of whom had received doses of < 1,800 cGy per fraction.

CONCLUSIONS

Very high radiation dose treatments were tolerated in this population of medically inoperable patients with stage I NSCLC using ESR techniques.

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.

Stereotactic single-dose radiotherapy of stage I non-small-cell lung cancer (NSCLC)

PURPOSE

The treatment of early-stage lung cancers is a primary domain of thoracic surgery, leading to persuasive results. In patients with medical contraindications, radiotherapy is an alternative, although with considerably worse outcome. Radiotherapy is associated with the risk of severe acute side effects and a permanent decrease of lung function. By the introduction of an extracranial stereotactic treatment technique, the amount of normal tissue in the high-dose region can be reduced, allowing the performance of single-dose treatment with high, biologically effective doses.

METHODS AND MATERIALS

Between October 1998 and May 2001, 10 patients with histologically confirmed Stage I non-small-cell lung cancer were treated with stereotactic single-dose radiotherapy. A self-developed stereotactic frame was used for patient positioning and navigation. Total doses applied ranged from 19 to 26 Gy. After treatment, regular CT-based follow-up was performed.

RESULTS

During a median follow-up period of 14.9 months, the tumors in 8 of 10 patients were locally controlled. The actuarial overall survival was 80% and 64%, respectively, 12 and 24 months after therapy. Actuarial local recurrence-free survival reached 88.9% and 71.1%, respectively. Therapy-related perifocal normal-tissue reaction occurred in 70% of all treated patients, although no major clinical symptoms were seen. In 5 patients, systemic metastases were found during follow-up; 1 patient developed suspect mediastinal lymph nodes.

CONCLUSION

Stereotactic single-fraction radiotherapy is a feasible, safe, and effective procedure for the treatment of Stage I non-small-cell lung cancer. It promises high local control with a reduced overall treatment time. However, further investigation in a larger patient collective with extended follow-up is necessary.

Stereotactic body frame based fractionated radiosurgery on consecutive days for primary or metastatic tumors in the lung

To evaluate the feasibility and treatment outcomes of stereotactic radiosurgery (SRS) using a stereotactic body frame (Precision Therapy), we prospectively reviewed 34 tumors of the 28 patients with primary or metastatic intrathoracic lung tumors. Eligible patients included were nine with primary lung cancer and 19 with metastatic tumors from the lung, liver, and many other organs. A single dose of 10 Gy to the clinical target volume (CTV) was delivered to a total dose of 30-40 Gy with three to four fractions. Four to eight coplanar or non-coplanar static fields were generated to adequately cover the planning target volume (PTV) as well as to exclude the critical structures as much as possible. More than 90% of the PTV was delivered the prescribed dose in the majority of cases (average; 96%, range; 74-100%). The mean PTV was 41.4 cm(3) ranging from 4.4 to 230 cm(3). Set-up error was within 5 mm in all directions (X, Y, Z axis). The response was evaluated by using a chest CT and/or 18FDG-PET scans after SRS treatment, 11 patients (39%) showed complete response, 12 (43%) partial response (decrease of more than 50% of the tumor volume), and four patients showed minimally decreased tumor volume or stable disease, but one patient showed progression disease. With a median follow-up period of 18 months, a local disease progression free interval was ranging from 7 to 35 months. Although all patients developed grade one radiation pneumonitis within 3 months, none had symptomatic or serious late complications after completing SRS treatment. Given these observations, it is concluded that the stereotactic body frame based SRS is a safe and effective treatment modality for the local management of primary or metastatic lung tumors. However, the optimum total dose and fractionation schedule used should be determined after the longer follow-up of these results.

Tolerance of organs at risk in small-volume, hypofractionated, image-guided radiotherapy for primary and metastatic lung cancers

PURPOSE

To determine the organ at risk and the maximum tolerated dose (MTD) of radiation that could be delivered to lung cancer using small-volume, image-guided radiotherapy (IGRT) using hypofractionated, coplanar, and noncoplanar multiple fields.

MATERIALS AND METHODS

Patients with measurable lung cancer (except small-cell lung cancer) 6 cm or less in diameter for whom surgery was not indicated were eligible for this study. Internal target volume was determined using averaged CT under normal breathing, and for patients with large respiratory motion, using two additional CT scans with breath-holding at the expiratory and inspiratory phases in the same table position. Patients were localized at the isocenter after three-dimensional treatment planning. Their setup was corrected by comparing two linacographies that were orthogonal at the isocenter with corresponding digitally reconstructed images. Megavoltage X-rays using noncoplanar multiple static ports or arcs were used to cover the parenchymal tumor mass. Prophylactic nodal irradiation was not performed. The radiation dose was started at 60 Gy in 8 fractions over 2 weeks (60 Gy/8 Fr/2 weeks) for peripheral lesions 3.0 cm or less, and at 48 Gy/8 Fr/2 weeks at the isocenter for central lesions or tumors more than 3.0 cm at their greatest dimension.

RESULTS

Fifty-seven lesions in 45 patients were treated. Tumor size ranged from 0.6 to 6.0 cm, with a median of 2.6 cm. Using the starting dose, 1 patient with a central lesion died of a radiation-induced ulcer in the esophagus after receiving 48 Gy/8 Fr at isocenter. Although the contour of esophagus received 80% or less of the prescribed dose in the planning, recontouring of esophagus in retrospective review revealed that 1 cc of esophagus might have received 42.5 Gy, with the maximum dose of 50.5 Gy. One patient with a peripheral lesion experienced Grade 2 pain at the internal chest wall or visceral pleura after receiving 54 Gy/8 Fr. No adverse respiratory reaction was noted in the symptoms or respiratory function tests. The 3-year local control rate was 80.4% +/- 7.1% (a standard error) with a median follow-up period of 17 months for survivors. Because of the Grade 5 toxicity, we have halted this Phase I/II study and are planning to rearrange the protocol setting accordingly. The 3-year local control rate was 69.6 +/- 10.6% for patients who received 48 Gy and 100% for patients who received 60 Gy (p = 0.0442).

CONCLUSIONS

Small-volume IGRT using 60 Gy in eight fractions is highly effective for the local control of lung tumors, but MTD has not been determined in this study. The organs at risk are extrapleural organs such as the esophagus and internal chest wall/visceral pleura rather than the pulmonary parenchyma in the present protocol setting. Consideration of the uncertainty in the contouring of normal structures is critically important, as is uncertainty in setup of patients and internal organ in the high-dose hypofractionated IGRT.

Tumor location, cirrhosis, and surgical history contribute to tumor movement in the liver, as measured during stereotactic irradiation using a real-time tumor-tracking radiotherapy system

PURPOSE

To investigate the three-dimensional (3D) intrafractional motion of liver tumors during real-time tumor-tracking radiotherapy (RTRT).

MATERIALS AND METHODS

The data of 20 patients with liver tumors were analyzed. Before treatment, a 2-mm gold marker was implanted near the tumor. The RTRT system used fluoroscopy image processor units to determine the 3D position of the implanted marker. A linear accelerator was triggered to irradiate the tumor only when the marker was located within a permitted region. The automatically recorded tumor-motion data were analyzed to determine the amplitude of the tumor motion, curve shape of the tumor motion, treatment efficiency, frequency of movement, and hysteresis. Each of the following clinical factors was evaluated to determine its contribution to the amplitude of movement: tumor position, existence of cirrhosis, surgical history, tumor volume, and distance between the isocenter and the marker.

RESULTS

The average amplitude of tumor motion in the 20 patients was 4 +/- 4 mm (range 1-12), 9 +/- 5 mm (range 2-19), and 5 +/- 3 mm (range 2-12) in the left-right, craniocaudal, and anterior-posterior (AP) direction, respectively. The tumor motion of the right lobe was significantly larger than that of the left lobe in the left-right and AP directions (p = 0.01). The tumor motion of the patients with liver cirrhosis was significantly larger than that of the patients without liver cirrhosis in the left-right and AP directions (p < 0.004). The tumor motion of the patients who had received partial hepatectomy was significantly smaller than that of the patients who had no history of any operation on the liver in the left-right and AP directions (p < 0.03). Thus, three of the five clinical factors examined (i.e., tumor position in the liver, cirrhosis, and history of surgery on the liver) significantly affected the tumor motion of the liver in the transaxial direction during stereotactic irradiation. Frequency analysis revealed that for 9 (45%) of the 20 tumors, the cardiac beat caused measurable motion. The 3D trajectory of the tumor showed hysteresis for 4 (20%) of the 20 tumors. The average treatment efficiency of RTRT was 40%.

CONCLUSIONS

Tumor location, cirrhosis, and history of surgery on the liver all had an impact on the intrafractional tumor motion of the liver in the transaxial direction. This finding should be helpful in determining the smallest possible margin in individual cases of radiotherapy for liver malignancy.

Dynamic conical conformal radiotherapy using a C-arm-mounted accelerator: dose distribution and clinical application

PURPOSE

The aim of this study was to solve anisotropy in the dose distributions from rotational conformal radiotherapy (RCRT) by using a C-arm-mounted accelerator.

MATERIALS AND METHODS

The linac head was designed to move along the C-arm with a maximum angle of 60 degrees (from a vertical position toward the gantry). Simultaneous rotation of the gantry creates a dynamic conical irradiation technique. Dynamic conical conformal radiation therapy (Dyconic CRT) was developed by combining the technique with continuous motion of a multileaf collimator. Dose distributions were measured in phantoms using film densitometry and compared with conventional RCRT. Dose distributions in actual radiation therapy patients are also presented.

RESULTS

Dyconic CRT enabled the precise delivery of noncoplanar beams without rotating the table. The measurements showed that three-dimensionally isotropic dose falloff was achieved with Dyconic CRT. Dose inhomogeneity in the sagittal direction with Dyconic CRT was compensated for by use of wedge filters.

CONCLUSIONS

The drawbacks of the dose distributions produced by RCRT were overcome with the use of Dyconic CRT.

Stereotactic radiosurgery for lung tumors: preliminary report of a phase I trial

BACKGROUND

Stereotactic radiosurgery is well established for the treatment of intracranial neoplasms but its use for lung tumors is novel.

METHODS

Twenty-three patients with biopsy-proven lung tumors were recruited into a two-institution, dose-escalation, phase I clinical trial using a frameless stereotactic radiosurgery system (CyberKnife). Fifteen patients had primary lung tumors and 8 had metastatic tumors. The age range was 23 to 87 years (mean, 63 years). After undergoing computed tomography-guided percutaneous placement of two to four small metal fiducials directly into the tumor, patients received 1,500 cGY of radiation in a single fraction using a linear accelerator mounted on a computer-controlled robotic arm. Safety, feasibility, and efficacy were studied.

RESULTS

Nine patients were treated with a breath-holding technique, and 14 with a respiratory-gating, automated, robotic technique. Tumor size ranged from 1 to 5 cm in maximal diameter. There were four complications related to fiducial placement: three pneumothoraces requiring chest tube insertion and one emphysema exacerbation. There were no grade 3 to 5 radiation-related complications. Follow-up ranged from 1 to 26 months (mean, 7.0 months). Radiographic response was scored as complete in 2 patients, partial in 15, stable in 4, and progressive in 2. Four patients died of non-treatment-related causes at 1, 5, 9, and 11 months after radiation.

CONCLUSIONS

Single-fraction stereotactic radiosurgery is safe and feasible for the treatment of selected lung tumors. Additional studies are planned to investigate the optimal radiation dose, best motion-suppression technique, and overall treatment efficacy.

Extracranial stereotactic radiation delivery: expansion of technology beyond the brain

The development of improved immobilization systems, and a greater understanding of the radiobiologic considerations associated with stereotactic radiotherapy has recently led to the clinical implementation of this technology to extracranial sites. The shared principles of targeting and treatment delivery has led to a greater understanding of the potential role this therapy may have in the management of extracranial disease. This article will review, the radiobiologic considerations and the basic principles of physics and dosimetry that help govern the utilization of extracranial stereotactic radiotherapy. In addition, this article will summarize the data that exists in the literature to date, that has documented the rationale, and efficacy of this novel therapeutic approach.

Extracranial stereotactic radiotherapy: evaluation of PTV coverage and dose conformity

During the past few years the concept of cranial stereotactic radiotherapy has been successfully extended to extracranial tumoral targets. In our department, hypofractionated treatment of tumours in lung, liver, abdomen, and pelvis is performed in the Stereotactic Body Frame (ELEKTA Instrument AB) since 1997. We present the evaluation of 63 consecutively treated targets (22 lung, 21 liver, 20 abdomen/pelvis) in 58 patients with respect to dose coverage of the planning target volume (PTV) as well as conformity of the dose distribution. The mean PTV coverage was found to be 96.3% +/- 2.3% (lung), 95.0% +/- 4.5% (liver), and 92.1% +/- 5.2% (abdomen/pelvis). For the so-called conformation number we obtained values of 0.73 +/- 0.09 (lung), 0.77 +/- 0.10 (liver), and 0.70 +/- 0.08 (abdomen/pelvis). The results show that highly conformal treatment techniques can be applied also in extracranial stereotactic radiotherapy. This is primarily due to the relatively simple geometrical shape of most of the targets. Especially lung and liver targets turned out to be approximately spherically/cylindrically shaped, so that the dose distribution can be easily tailored by rotational fields.

How should we describe the radioblologic effect of extracranial stereotactic radlosurgery: equivalent uniform dose or tumor control probability?

Extracranial stereotactic radiosurgery (ESR) is now undergoing clinical investigation at numerous institutions as a treatment for solitary malignant lesions. Because there is no standard ESR technique, the same minimum dose might be applied through widely variable target dose-volume histograms. For multicenter trials of ESR or interinstitutional comparisons, a reliable index of radiobiological dose equivalency might facilitate the evaluation of dose-response relationships. Equivalent uniform dose (EUD) and tumor control probability (TCP) were considered for this application. While EUD appears more robust for the prospective description of ESR, TCP is expected to remain more valuable for a post hoc estimation of radiosensitivity parameters.

What can we expect from dose escalation using proton beams?

It has been demonstrated without doubt in the literature, including elsewhere in this issue, that much better conformal dose distributions in radiation therapy can be obtained with proton beams than with photons (X-rays) or electrons. It is also clear that this remains entirely true--for the fundamental reason of particle range--even after the latest and projected developments in computer-generated IMRT (intensity-modulated radiation therapy) photon dose escalation are fully considered. We consider several examples of tumour dose-response curves that illustrate the quite large gains to be obtained when dose escalation can be achieved, if normal tissue complications can also be avoided. Two contrasting types of tumour are considered in detail, prostate tumours and non-small-cell lung carcinomas. There is a considerable way to go yet to achieve really high non-recurrence rates, especially in the lung tumours. Proton beams would make this progress much safer and more effective than any variants with photons.

Impact of target reproducibility on tumor dose in stereotactic radiotherapy of targets in the lung and liver

BACKGROUND AND PURPOSE

Previous analyses of target reproducibility in extracranial stereotactic radiotherapy have revealed standard security margins for planning target volume (PTV) definition of 5mm in axial and 5-10mm in longitudinal direction. In this study the reproducibility of the clinical target volume (CTV) of lung and liver tumors within the PTV over the complete course of hypofractionated treatment is evaluated. The impact of target mobility on dose to the CTV is assessed by dose-volume histograms (DVH).

MATERIALS AND METHODS

Twenty-two pulmonary and 21 hepatic targets were treated with three stereotactic fractions of 10 Gy to the PTV-enclosing 100%-isodose with normalization to 150% at the isocenter. A conformal dose distribution was related to the PTV, which was defined by margins of 5-10mm added to the CTV. Prior to each fraction a computed tomography (CT)-simulation over the complete target volume was performed resulting in a total of 60 CT-simulations for lung and 58 CT-simulations for hepatic targets. The CTV from each CT-simulation was segmented and matched with the CT-study used for treatment planning. A DVH of the simulated CTV was calculated for each fraction. The target coverage (TC) of dose to the simulated CTV was defined as the proportion of the CTV receiving at least the reference dose (100%).

RESULTS

A decrease of TC to <95% was found in 3/60 simulations (5%) of pulmonary and 7/58 simulations (12%) of hepatic targets. In two of 22 pulmonary targets (9%) and in four of 21 hepatic targets (19%) a TC of <95% occurred in at least one fraction. At risk for a decreased TC <95% were pulmonary targets with increased breathing mobility and hepatic targets with a CTV exceeding 100 cm(3).

CONCLUSIONS

Target reproducibility was precise within the reference isodose in 91% of lung and 81% of liver tumors with a TC of the complete CTV >or=95% at each fraction of treatment. Pulmonary targets with increased breathing mobility and liver tumors >100 cm(3) are at risk for target deviation exceeding the standard security margins for PTV-definition at least for one fraction and require individual evaluation of sufficient margins.

Real-time tumor-tracking radiation therapy for lung carcinoma by the aid of insertion of a gold marker using bronchofiberscopy

BACKGROUND

The authors developed fluoroscopic real-time tumor-tracking radiation therapy (RTRT) by insertion of a gold marker using bronchofiberscopy to reduce uncertainties in organ motion and set-up error in external radiotherapy for moving tumors. The purpose of the current study was to evaluate RTRT's feasibility in lung carcinoma treatment.

METHODS

The three-dimensional position of a 1.0-2.0 mm gold marker in or near the tumor was detected by two sets of fluoroscopies every 0.03 seconds. The treatment beam was gated to irradiate the tumor only when the position of the marker coincided with its planned position using the RTRT system. Bronchofiberscopic equipment for insertion of the marker into the lung tumor was developed and used for 20 lung tumors in 18 patients. Patients were given high dose hypofractionated focal irradiation (35-48 Gy in 4-8 fractions in 4-10 days) with a planning target volume margin of 5 mm for the tumor.

RESULTS

The markers were successfully inserted and maintained at the inserted position during and after the radiotherapy in 14 (88%) of 16 peripheral-type lung tumors and in none of four central-type lung tumors, indicating that this method of RTRT was not feasible for central-type lung tumors. Tracking of the marker was successfully performed in 1 of 2 tumors with a 1.0 mm marker and in all of 12 tumors with a 1.5-2.0 mm marker. On the whole, 13 (65%) of the 20 tumors were successfully treated with RTRT. Local tumor control was achieved and maintained for all 12 patients (13 tumors), who were treated with RTRT, with a median followup of 9 months (range, 5-15). Localized radiation pneumonitis was found radiographically at the lung volume that was irradiated with about 20 Gy, without symptoms in all but one patient.

CONCLUSIONS

The insertion of a gold marker into or near peripheral-type lung tumors using bronchofiberscopy is a feasible and safe technique. Excellent initial response and low incidence of clinical complications suggest that the high dose hypofractionated focal irradiation using the RTRT system can be a good local treatment for peripheral-type lung tumors.

Small-volume image-guided radiotherapy using hypofractionated, coplanar, and noncoplanar multiple fields for patients with inoperable Stage I nonsmall cell lung carcinomas

BACKGROUND

Occasionally, medically compromised and/or elderly patients with nonsmall cell lung carcinomas (NSCLCs) cannot be treated surgically. We investigated small-volume hypofractionated image-guided radiotherapy (IGRT) without the need for breath control in patients with inoperable Stage I NSCLCs.

METHODS

Between September 1996 and September 1999, 22 patients with Stage I NSCLCs, including 19 males and 3 females, were treated with IGRT. Among these patients, there were 13 Stage IA and 9 Stage IB tumors. The tumors ranged in size from 14.2 to 58.5 mm, with a median size of 26.7 mm. Of the 22 patients, 19 were unfit for surgical treatment due to poor pulmonary function, complications, and/or advanced age and 3 refused surgery. Computed tomographic scans (CT) of the primary tumor were taken during three respiratory phases and they were analyzed to determine the planning target volume, which included only the primary tumor with allowances for respiratory movement. The radiation doses administered at the edge of the moving tumor during normal breathing were 80% of the prescribed dose, either 48 or 60 Gy given in eight fractions over 2 weeks. Clinical evaluation, chest CT scan, and pulmonary function tests were performed before irradiation and at regular intervals for the post-IGRT follow-up. The median follow-up period was 24 months (range, 2-44 months; mean, 21.8 months) (at least 24 months for survivors).

RESULTS

Of 17 tumors assessed at the initial follow-up 2-6 months after treatment (5 complete responses, 11 partial responses, and 1 progressive disease), 16 (94%) were controlled locally. One local recurrence was observed during the follow-up. The lung carcinoma-specific survival rate at 1 year was 94% and the 1-year actuarial recurrence-free survival rate was 71%. The lung carcinoma-specific survival rate at 2 years was 73% and the 2-year actuarial recurrence-free survival rate was 67%. The treatment was well tolerated and no major side effects were observed. Localized radiation pneumonitis was observed in all patients who were examined by CT scan, but the patients were asymptomatic. Parameters of pulmonary function, including vital capacity, total lung capacity, and diffusion capacity for carbon monoxide, decreased very little or not at all, indicating that IGRT rarely deteriorated pulmonary functions.

CONCLUSIONS

Small-volume hypofractionated IGRT without breath control is a feasible and beneficial method for the curative treatment of patients with Stage I NSCLCs. It has the potential of a high local tumor control rate and low morbidity.

Stereotactic single high dose irradiation of lung tumors under respiratory gating

PURPOSE

To investigate the feasibility of a stereotactic single high dose irradiation of lung tumors under respiratory gating and the clinical response.

METHODS AND MATERIALS

Twenty-three malignant lung tumors less than 40mm in diameter were treated by a single fractional irradiation.

RESULTS AND DISCUSSION

Local regrowth was seen in three of ten tumors irradiated less than 30Gy, the minimal dose. Only one regrowth was observed in the tumors treated by 30Gy of with a follow up length of 3-24 months. Apparently 30Gy is able to control the lung tumors with a diameter less than 40mm.

Daily targeting of intrahepatic tumors for radiotherapy

INTRODUCTION

A system has been developed for daily targeting of intrahepatic tumors using a combination of ventilatory immobilization, in-room diagnostic imaging, and on-line setup adjustment. By reducing geometric position uncertainty, as well as organ movement, this system permits reduction of margins and thus potentially higher treatment doses. This paper reports our initial experience treating 8 patients with focal liver tumors using this system.

METHODS AND MATERIALS

The system includes diagnostic X-ray tubes mounted on the wall and ceiling of a treatment room, an active matrix flat panel imager, in-room control for image acquisition and setup adjustment, and a ventilatory immobilization system via active breathing control (ABC). Eight patients participated in the study, two using an early prototype ABC unit, and the remaining six with a commercial ABC system and improved setup measurement tools. Treatment margins were reduced, and dose consequently increased because of increased confidence in target position under this protocol. After daily setup via skin marks, orthogonal radiographs were acquired at suspended ventilation. The images were aligned to the CT model using the diaphragm for inferior-superior (IS) alignment, and the skeleton for left-right (LR) and anterior-posterior (AP) alignment. Adjustments were made for positioning errors greater than a threshold (3 or 5 mm). After treatment, retrospective analysis determined the final setup accuracy, as well as the error in initial setup measurement performed before setup adjustment.

RESULTS

Two hundred sixty-two treatment fractions were delivered on eight patients, with 171 treatments requiring repositioning. Typical treatment times were 25-30 min. Patients were able to tolerate ABC throughout the course of treatment. Breath holds up to 35 s long were used for treatment. The use of on-line imaging and setup adjustment reduced setup errors (sigma) from 4.0 mm (LR), 6.7 mm (IS), and 3.8 mm (AP) to 2.1 mm (LR), 3.5 mm (IS), and 2.3 mm (AP). Prescribed doses were increased using this system by an average of 5 Gy.

CONCLUSIONS

Daily targeting of intrahepatic targets has been demonstrated to be feasible. The potential for reduction in treatment margin and consequential safe dose escalation has been demonstrated, while maintaining reasonable treatment delivery times.

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.

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.

Partial irradiation of the liver

The use of three-dimensional radiotherapy (RT) and the prospective follow-up of patients for radiation-induced liver disease (RILD) have led to a more quantitative understanding of the partial organ tolerance of the liver compared with previous estimates based on clinical judgment alone. Parameters of both the Lyman normal tissue complication probability (NTCP) model and a local damage-organ injury (D-I) NTCP model have been fit to clinical data from patients who have received hepatic radiation. Based on analyses of over 180 patients, the liver exhibits a large volume effect and a low threshold volume for RILD. Mean liver dose is associated with RILD, and no cases of RILD have been reported in patients with a mean liver dose of less than 31 Gy. Most recent estimates of the partial liver tolerance to RT suggest that if less than 25% of the normal liver is treated with RT, then there may be no upper limit on dose associated with RILD. Estimates of the liver doses associated with a 5% risk of RILD for uniform irradiation of one third, two thirds, and the whole liver are 90 Gy, 47 Gy, and 31 Gy, respectively.

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.

Calibration of three-dimensional ultrasound images for image-guided radiation therapy

A new technique of patient positioning for radiotherapy/radiosurgery of extracranial tumours using three-dimensional (3D) ultrasound images has been developed. The ultrasound probe position is tracked within the treatment room via infrared light emitting diodes (IRLEDs) attached to the probe. In order to retrieve the corresponding room position of the ultrasound image, we developed an initial ultrasound probe calibration technique for both 2D and 3D ultrasound systems. This technique is based on knowledge of points in both room and image coordinates. We first tested the performance of three algorithms in retrieving geometrical transformations using synthetic data with different noise levels. Closed form solution algorithms (singular value decomposition and Horn's quaternion algorithms) were shown to outperform the Hooke and Jeeves iterative algorithm in both speed and accuracy. Furthermore, these simulations show that for a random noise level of 2.5, 5, 7.5 and 10 mm, the number of points required for a transformation accuracy better than 1 mm is 25, 100, 200 and 500 points respectively. Finally, we verified the tracking accuracy of this system using a specially designed ultrasound phantom. Since ultrasound images have a high noise level, we designed an ultrasound phantom that provides a large number of points for the calibration. This tissue equivalent phantom is made of nylon wires, and its room position is optically tracked using IRLEDs. By obtaining multiple images through the nylon wires, the calibration technique uses an average of 300 points for 3D ultrasound volumes and 200 for 2D ultrasound images, and its stability is very good for both rotation (standard deviation: 0.4 degrees) and translation (standard deviation: 0.3 mm) transformations. After this initial calibration procedure, the position of any voxel in the ultrasound image volume can be determined in world space, thereby allowing real-time image guidance of therapeutic procedures. Finally, the overall tracking accuracy of our 3D ultrasound image-guided positioning system was measured to be on average 0.2 mm, 0.9 mm and 0.6 mm for the AP, lateral and axial directions respectively.

Stereotactic single-dose radiation therapy of liver tumors: results of a phase I/II trial

PURPOSE

To investigate the feasibility and the clinical response of a stereotactic single-dose radiation treatment for liver tumors.

PATIENTS AND METHODS

Between April 1997 and September 1999, a stereotactic single-dose radiation treatment of 60 liver tumors (four primary tumors, 56 metastases) in 37 patients was performed. Patients were positioned in an individually shaped vacuum pillow. The applied dose was escalated from 14 to 26 Gy (reference point), with the 80% isodose surrounding the planning target volume. Median tumor size was 10 cm(3) (range, 1 to 132 cm(3)). The morbidity, clinical outcome, laboratory findings, and response as seen on computed tomography (CT) scan were evaluated.

RESULTS

Follow-up data could be obtained from 55 treated tumors (35 patients). The median follow-up period was 5.7 months (range, 1.0 to 26.1 months; mean, 9.5 months). The treatment was well tolerated by all patients. There were no major side effects. Fifty-four (98%) of 55 tumors were locally controlled after 6 weeks at the initial follow-up based on the CT findings (22 cases of stable disease, 28 partial responses, and four complete responses). After a dose-escalating and learning phase, the actuarial local tumor control rate was 81% at 18 months after therapy. A total of 12 local failures were observed during follow-up. So far, the longest local tumor control is 26.1 months.

CONCLUSION

Stereotactic single-dose radiation therapy is a feasible method for the treatment of singular inoperable liver metastases with the potential of a high local tumor control rate and low morbidity.

Stereotactic radiotherapy of extracranial targets: CT-simulation and accuracy of treatment in the stereotactic body frame

BACKGROUND AND PURPOSE

Evaluation of set-up accuracy and analysis of target reproducibility in the stereotactic body frame (SBF), designed by Blomgren and Lax from Karolinska Hospital, Stockholm. Different types of targets were analyzed for the risk of target deviation. The correlation of target deviation to bony structures was analyzed to evaluate the value of bones as reference structures for isocenter verification.

MATERIALS AND METHODS

Thirty patients with 32 targets were treated in the SBF for primary or metastatic peripheral lung cancer, liver metastases, abdominal and pelvic tumor recurrences or bone metastases. Set-up accuracy and target mobility were evaluated by CT-simulation and port films. The contours of the target at isocenter level, bony structures and body outline were compared by matching the CT-slices for treatment planning and simulation using the stereotactic coordinates of the SBF as external reference system. The matching procedure was performed by using a 3D treatment planning program.

RESULTS

Set-up accuracy represented by bony structures revealed standard deviations (SD) of 3.5 mm in longitudinal, 2.2 mm in anterior-posterior and 3.9 mm in lateral directions. Target reproducibility showed a SD of 4.4 mm in longitudinal, 3.4 mm ap and 3.3 mm in lateral direction prior to correction. Correlation of target deviation to bones ranged from 33% (soft tissue targets) to 100% (bones).

CONCLUSION

A security margin of 5 mm for PTV definition is sufficient, if CT simulation is performed prior to each treatment to correct larger target deviations or set-up errors. Isocenter verification relative to bony structures is only safe for bony targets but not for soft tissue targets.

Intrafractional tumor position stability during computed tomography (CT)-guided frameless stereotactic radiation therapy for lung or liver cancers with a fusion of CT and linear accelerator (FOCAL) unit

PURPOSE

To evaluate intrafractional tumor position stability during computed tomography (CT)-guided frameless stereotactic radiation therapy (SRT) for lung or liver cancers, we checked repeated CT scanning, with a fusion of CT and linear accelerator (FOCAL) unit.

METHODS AND MATERIALS

The FOCAL unit is a combination of a linear accelerator (Linac), CT scanner, X-ray simulator (X-S), and carbon table, and is designed to achieve CT-guided SRT with daily CT positioning followed by immediate irradiation while patients keep reduced shallow respirations. To evaluate intrafractional tumor position stability, 50 lung or liver lesions in 20 patients were checked by repeated CT scanning just before and after irradiation, and the obtained images were compared.

RESULTS

There was no case with the intrafractional error judged to be greater than 10 mm. In 68% of cases, the intrafractional positioning errors were negligible (0-5 mm).

CONCLUSIONS

Using the FOCAL unit, SRT for lung or liver cancers could be performed with intrafractional positioning errors not greater than 10 mm.

Megavoltage CT-assisted stereotactic radiosurgery for thoracic tumors: original research in the treatment of thoracic neoplasms

PURPOSE

The aim of the study was to evaluate the efficacy of stereotactic radiosurgery (SRS) for thoracic tumors with megavoltage computed tomography (MVCT) from the point of view of symptom palliation as well as local control.

METHODS AND MATERIALS

MVCT-assisted positioning verification and real-time monitoring for a multileaf collimator (MLC) were used to enhance the accuracy of the thoracic SRS. Twenty-two thoracic tumors in 15 patients underwent the present treatment. All but 1 tumor were metastases from various primary malignancies. Eleven patients were symptomatic. The treatment site was the chest wall/pleura in 10 tumors, and the lung in 12 tumors. The median volume of the clinical target was 4.5 cc and the median peripheral dose was 20 Gy, for the lung tumors. For the chest wall/pleura tumors, the median volume of the clinical target was 40 cc and the median peripheral dose was 20 Gy. Conventional fractionated conformal radiation therapy (CRT) followed SRS in 10 tumors.

RESULTS

Of 21 tumors eligible for evaluation, there were 13 with complete responses, 6 with partial responses, and 2 without response. Duration of local control ranged from 0.6 to 82 months with a median of 8 months, with only one local recurrence seen. Immediate palliation was obtained in most symptomatic patients. Interstitial changes in the lung were limited. Autopsy performed for a patient revealed remarkable histologic effects with minimal injuries to the lung.

CONCLUSION

The geometric accuracy of MVCT-assisted SRS appeared to enhance the clinical efficacy and safety of treatment to thoracic malignancies.