An evaluation of two techniques for beam intensity modulation in patients irradiated for stage III non-small cell lung cancer

Functional lung volume mapping with perfusion Single-Photon Emission Computed Tomography scan for radiotherapy planning in patients with locally advanced nonsmall cell lung cancer

OBJECTIVES

Radical chemotherapy-radiotherapy represents the standard treatment for locally-advanced nonsmall cell lung cancer (NSCLC). Conventional radiotherapy achieves limited local tumor control, but dose escalation to the primary tumor is prevented by radiotherapy-induced toxicity. The aim of this study was to evaluate feasibility of tailored intensity-modulated radiotherapy (IMRT) planning based on lung single-photon emission computed tomography (SPECT) perfusion data and to compare functional and conventional dose-volume parameters.

METHODS

A total of 21 patients were prospectively enrolled. Patients underwent IMRT treatment with 2 Gy/fraction (median total dose of 60 Gy). Lung perfusion SPECT images were acquired before radiotherapy and 3 and 6 months after radiotherapy completion. SPECT and planning computed tomography images were co-registered using MIM-MAESTRO software with 3D-PET Edge algorithm. Lung volumes were defined anatomically as total lung and functionally as total not functional lung and total functional lung. Dose-volume histograms were calculated using QUANTEC constraints [mean lung dose (MLD)<20 Gy, V20<20%]. For each patient, conventional and functional radiotherapy plans were generated and compared.

RESULTS

A total of 19 of 21 patients with NSCLC were included (mean age 66 years, 11 stage IIIA, 8 stage IIIB), 12/19 patients completed the 6-months follow-up. A significant reduction of mean V20 was observed in functional radiotherapy planning compared to conventional plan (405.9 cc, P < 0.001). Mean MLD was also lower in the SPECT-based plans, but the difference was not statistically relevant (0.8 Gy, P = 0.299). G2 radiation pneumonitis was observed in two patients.

CONCLUSIONS

Functional radiotherapy planning allowed to decrease functional lung irradiation compared to conventional planning. The possibility to limit radiotherapy-induced toxicity could allow us to perform an effective dose-escalation to target volume.

Radiation-induced lung injury: current evidence

Chemo-radiotherapy and systemic therapies have proven satisfactory outcomes as standard treatments for various thoracic malignancies; however, adverse pulmonary effects, like pneumonitis, can be life-threatening. Pneumonitis is caused by direct cytotoxic effect, oxidative stress, and immune-mediated injury. Radiotherapy Induced Lung Injury (RILI) encompasses two phases: an early phase known as Radiation Pneumonitis (RP), characterized by acute lung tissue inflammation as a result of exposure to radiation; and a late phase called Radiation Fibrosis (RF), a clinical syndrome that results from chronic pulmonary tissue damage. Currently, diagnoses are made by exclusion using clinical assessment and radiological findings. Pulmonary function tests have constituted a significant step in evaluating lung function status during radiotherapy and useful predictive tools to avoid complications or limit toxicity. Systemic corticosteroids are widely used to treat pneumonitis complications, but its use must be standardized, and consider in the prophylaxis setting given the fatal outcome of this adverse event. This review aims to discuss the clinicopathological features of pneumonitis and provide practical clinical recommendations for prevention, diagnosis, and management.

Planning and delivery of intensity-modulated radiation therapy

Intensity modulated radiation therapy (IMRT) is an advanced form of external beam radiation therapy. IMRT offers an additional dimension of freedom as compared with field shaping in three-dimensional conformal radiation therapy because the radiation intensities within a radiation field can be varied according to the preferences of locations within a given beam direction from which the radiation is directed to the tumor. This added freedom allows the treatment planning system to better shape the radiation doses to conform to the target volume while sparing surrounding normal structures. The resulting dosimetric advantage has shown to translate into clinical advantages of improving local and regional tumor control. It also offers a valuable mechanism for dose escalation to tumors while simultaneously reducing radiation toxicities to the surrounding normal tissue and sensitive structures. In less than a decade, IMRT has become common practice in radiation oncology. Looking forward, the authors wonder if IMRT has matured to such a point that the room for further improvement has diminished and so it is pertinent to ask what the future will hold for IMRT. This article attempts to look from the perspective of the current state of the technology to predict the immediate trends and the future directions. This article will (1) review the clinical experience of IMRT; (2) review what we learned in IMRT planning; (3) review different treatment delivery techniques; and finally, (4) predict the areas of advancements in the years to come.

A potential to reduce pulmonary toxicity: The use of perfusion SPECT with IMRT for functional lung avoidance in radiotherapy of non-small cell lung cancer

BACKGROUND AND PURPOSE

The study aimed to examine specific avoidance of functional lung (FL) defined by a single photon emission computerized tomography (SPECT) lung perfusion scan, using intensity modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3-DCRT) in patients with non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Patients with NSCLC underwent planning computerized tomography (CT) and lung perfusion SPECT scan in the treatment position using fiducial markers to allow co-registration in the treatment planning system. Radiotherapy (RT) volumes were delineated on the CT scan. FL was defined using co-registered SPECT images. Two inverse coplanar RT plans were generated for each patient: 4-field 3-DCRT and 5-field step-and-shoot IMRT. 3-DCRT plans were created using automated AutoPlan optimisation software, and IMRT plans were generated employing Pinnacle(3) treatment planning system (Philips Radiation Oncology Systems). All plans were prescribed to 64 Gy in 32 fractions using data for the 6 MV beam from an Elekta linear accelerator. The objectives for both plans were to minimize the volume of FL irradiated to 20 Gy (fV(20)) and dose variation within the planning target volume (PTV). A spinal cord dose was constrained to 46 Gy. Volume of PTV receiving 90% of the prescribed dose (PTV(90)), fV(20), and functional mean lung dose (fMLD) were recorded. The PTV(90)/fV(20) ratio was used to account for variations in both measures, where a higher value represented a better plan.

RESULTS

Thirty-four RT plans of 17 patients with stage I-IIIB NSCLC suitable for radical RT were analysed. In 6 patients with stage I-II disease there was no improvement in PTV(90), fV(20), PTV/fV(20) ratio and fMLD using IMRT compared to 3-DCRT. In 11 patients with stage IIIA-B disease, the PTV was equally well covered with IMRT and 3-DCRT plans, with IMRT producing better PTV(90)/fV(20) ratio (mean ratio - 7.2 vs. 5.3, respectively, p=0.001) and reduced fMLD figures compared to 3-DCRT (mean value - 11.5 vs. 14.3 Gy, p=0.001). This was due to reduction in fV(20) while maintaining PTV coverage.

CONCLUSION

The use of IMRT compared to 3-DCRT improves the avoidance of FL defined by perfusion SPECT scan in selected patients with locally advanced NSCLC. If the dose to FL is shown to be the primary determinant of lung toxicity, IMRT would allow for effective dose escalation by specific avoidance of FL.

Radiation pneumonitis and pulmonary fibrosis in non-small-cell lung cancer: pulmonary function, prediction, and prevention

Although radiotherapy improves locoregional control and survival in patients with non-small-cell lung cancer, radiation pneumonitis is a common treatment-related toxicity. Many pulmonary function tests are not significantly altered by pulmonary toxicity of irradiation, but reductions in D(L(CO)), the diffusing capacity of carbon monoxide, are more commonly associated with pneumonitis. Several patient-specific factors (e.g. age, smoking history, tumor location, performance score, gender) and treatment-specific factors (e.g. chemotherapy regimen and dose) have been proposed as potential predictors of the risk of radiation pneumonitis, but these have not been consistently demonstrated across different studies. The risk of radiation pneumonitis also seems to increase as the cumulative dose of radiation to normal lung tissue increases, as measured by dose-volume histograms. However, controversy persists about which dosimetric parameter optimally predicts the risk of radiation pneumonitis, and whether the volume of lung or the dose of radiation is more important. Radiation oncologists ought to consider these dosimetric factors when designing radiation treatment plans for all patients who receive thoracic radiotherapy. Newer radiotherapy techniques and technologies may reduce the exposure of normal lung to irradiation. Several medications have also been evaluated for their ability to reduce radiation pneumonitis in animals and humans, including corticosteroids, amifostine, ACE inhibitors or angiotensin II type 1 receptor blockers, pentoxifylline, melatonin, carvedilol, and manganese superoxide dismutase-plasmid/liposome. Additional research is warranted to determine the efficacy of these medications and identify nonpharmacologic strategies to predict and prevent radiation pneumonitis.

Use of CD-ROM–based tool for analyzing contouring variations in involved-field radiotherapy for Stage III NSCLC

BACKGROUND

Interclinician variability in defining target volumes is a problem in conformal radiotherapy. A CD-ROM-based contouring tool was used to conduct a dummy run in an international trial of involved-field chemoradiotherapy for Stage III non-small-cell lung cancer.

METHODS AND MATERIALS

The CT scan of an eligible patient was installed on an "auto-run" CD-ROM incorporating a contouring program based on ImageJ for Windows, which runs on any personal computer equipped with a CD-ROM drive. This tool was initially piloted at four academic centers and was subsequently mailed, together with all relevant clinical, radiologic, and positron emission tomography findings, to all participating centers in the international trial. Clinicians were instructed to contour separate gross tumor volumes (GTVs) for the tumor and two enlarged nodes and a clinical target volume for the hilus. A reference "consensus" target volume for each target was jointly generated by three other clinicians.

RESULTS

The data received from the four academic centers and 16 study participants were suitable for analysis. Data from one center was unsuitable for detailed analysis because the target volumes were contoured at 1.2-cm intervals. GTVs were available for a total of 21 tumors and 19 nodes, and 15 hilar clinical target volumes were available. The mean GTV of the primary tumor was 13.6 cm(3) (SD, 5.2; median, 12.3; range, 8.3-26.9). The variation in the center of the mass relative to the mean center of the mass in the left-right, ventrodorsal, and craniocaudal axes was 1.5, 0.4, and 1.0 mm, respectively. The largest volume variation was observed for the right hilar clinical target volume (mean, 33.7 cm(3); SD, 31.2; median, 20.3; range, 4.8-109.9). Smaller variations were observed for the subcarinal node (mean, GTV, 1.9 cm(3); SD, 1.2; median, 1.7; range, 0.5-5.3), except caudally where the node was difficult to distinguish from the pericardium. The "consensus" volumes for all targets were generally close to the median of the contoured values.

CONCLUSION

Most clinicians were able to use this CD-ROM tool to contour target volumes in compliance with the study protocol. The rapid completion of the dummy run indicated the suitability of this approach for quality assurance in multicenter clinical trials. Routine use of similar tools will reduce the risk that new techniques (or study objectives) are misunderstood and/or misapplied in clinical trials.

A treatment planning study evaluating a 'simultaneous integrated boost' technique for accelerated radiotherapy of stage III non-small cell lung cancer

PURPOSE

As local tumour control is poor in stage III non-small cell lung cancer (NSCLC), a radiotherapy planning study was performed to evaluate the potential for treatment acceleration by using a simultaneous integrated boost (SIB) technique in patients who had completed induction chemotherapy.

METHODS AND MATERIALS

Co-registered pre- and post-chemotherapy planning CT scans from 10 patients who showed tumour regression after induction chemotherapy were used to compare different treatment schedules: (a) a sequential boost plan delivering, in 2 Gy per fraction, 50 Gy to the pre-chemotherapy tumour volume, followed by a sequential boost of 20 Gy to the post-chemotherapy tumour volume; (b) a SIB technique in which the pre- and post-chemotherapy tumour volumes were treated to different dose levels during each treatment fraction using identical total doses and number of fractions as above; (c) progressively more hypofractionated schedules that delivered the SIB technique in 25 and 20 once-daily fractions; (d) the actual clinical treatment plan in which 70 Gy was delivered to the pre-chemotherapy tumour volume in 35 daily fractions. Differences in the fractionation schemes used for these plans were accounted for by using the normalised total dose (NTD) for comparison, thereby assuming an alpha/beta ratio of 10 Gy for tumour and 3 Gy for normal tissues. The risk of normal tissue toxicity was estimated using the average lung NTD, the lung volume receiving NTD > 20 Gy, the oesophageal volume receiving NTD > 50 Gy, and the length of full circumference irradiated to at least 50 Gy.

RESULTS

With respect to the sequential boost technique, the SIB technique improved the sparing of the normal tissues in all patients. In most patients, the SIB plan could also be delivered in 25 fractions without increasing the estimated normal tissue toxicity. With SIB25, the mean lung NTD was reduced from 12.1 to 11.7 Gy, and the fraction of healthy lung tissue receiving NTD > 20 Gy by 2% on average. Although the length and volume of oesophagus irradiated to at least 50 Gy increased for some of the patients, the observed values were less than that was the case for the actual delivered treatment. However, special care should be taken to avoid exceeding the spinal cord tolerance in patients whose tumours are located close to the cord.

CONCLUSIONS

A SIB technique that delivers at least 50 Gy to the pre-chemotherapy tumour volume permits accelerated radiotherapy in patients with stage III NSCLC without increasing the expected risks of normal tissue toxicity. By reducing the overall treatment time, the SIB technique may improve local tumour control and survival.

Literature-based recommendations for treatment planning and execution in high-dose radiotherapy for lung cancer

BACKGROUND AND PURPOSE

To review the literature on techniques used in high-dose radiotherapy of lung cancer in order to develop recommendations for clinical practice and for use in research protocols.

PATIENTS AND METHODS

A literature search was performed for articles and abstracts that were considered both clinically relevant and practical to use. The relevant information was arbitrarily categorized under the following headings: patient positioning, CT scanning, incorporating tumour mobility, definition of target volumes, radiotherapy planning, treatment delivery, and scoring of response and toxicity.

RESULTS

Recommendations were made for each of the above steps from the published literature. Although most of the recommended techniques have yet to be evaluated in multicenter clinical trials, their use in high-dose radiotherapy to the thorax appears to be rational on the basis of current evidence.

CONCLUSIONS

Recommendations for the clinical implementation of high-dose conformal radiotherapy for lung tumours were identified in the literature. Procedures that are still considered to be investigational were also highlighted.

Feasibility of sparing lung and other thoracic structures with intensity-modulated radiotherapy for non-small-cell lung cancer

PURPOSE

To investigate the possibility of using intensity-modulated radiotherapy (IMRT) to reduce the irradiated volumes of the normal lung and other critical structures in the treatment of non-small-cell lung cancer (NSCLC) and to investigate the effect of IMRT on the potential of spreading low doses to large volumes of normal tissues in such treatment.

METHODS AND MATERIALS

A retrospective treatment planning study was performed to compare IMRT and conventional three-dimensional conformal radiation therapy (3D-CRT) for 10 NSCLC patients (Stage I-IIIB). In the IMRT plans, three to nine coplanar beams were designed to treat 95% of the planning target volume with 63 Gy and to minimize the volumes of the normal lung, esophagus, heart, and spinal cord irradiated above their tolerance doses. The two types of plans were compared with respect to the planning target volume coverage, dose-volume histograms, and other dosimetric indexes of the normal structures.

RESULTS

Comparing the nine-beam IMRT plan with the 3D-CRT plan, the percentage of lung volume that received >20 Gy and the mean lung dose were reduced for all cases, with a median reduction of 8% and 2 Gy, respectively. An additional reduction of the >5-Gy volume and >10-Gy volume for the lung and thoracic tissue was more difficult with IMRT, although still possible using fewer beams in IMRT. The integral dose to the entire thorax was equivalent and even reduced for 8 of 10 cases using IMRT.

CONCLUSION

It is possible to reduce the volumes of low doses (such as the >10-Gy volume and >20-Gy volume) for thoracic normal tissues using IMRT. The increased integral dose and low-dose volumes can be avoided for IMRT if such concerns are addressed carefully in the inverse planning process and with optimization of the IMRT beam configuration.

Clinical use of intensity-modulated radiotherapy: part I

Intensity-modulated radiotherapy (IMRT) is a novel conformal radiotherapy technique which is gaining increasing clinical use worldwide. This article aims to summarize the published data pertaining to clinical indications of this therapy for head and neck, central nervous system, and lung tumours. The main indications in head and neck cancer are parotid gland sparing and dose escalation to tumours close to organs at risk. For central nervous system tumours, IMRT has been used to reduce normal tissue radiation by more conformal dose distributions. To date, the majority of reports concern patients treated in the context of clinical trials, and for most tumour types longer term follow up of treated patients will be required to confirm the clinical benefits of IMRT.

Dose and volume reduction for normal lung using intensity-modulated radiotherapy for advanced-stage non–small-cell lung cancer

PURPOSE

To investigate dosimetric improvements with respect to tumor-dose conformity and normal tissue sparing using intensity-modulated radiotherapy (IMRT) compared with three-dimensional conformal radiotherapy (3D-CRT) for advanced-stage non-small-cell lung cancer (NSCLC).

METHODS AND MATERIALS

Forty-one patients with Stage III-IV and recurrent NSCLC who previously underwent 3D-CRT were included. IMRT plans were designed to deliver 63 Gy to 95% of the planning target volume using nine equidistant coplanar 6-MV beams. Inverse planning was performed to minimize the volumes of normal lung, heart, esophagus, and spinal cord irradiated above their tolerance doses. Dose distributions and dosimetric indexes for the tumors and critical structures in both plans were computed and compared.

RESULTS

Using IMRT, the median absolute reduction in the percentage of lung volume irradiated to >10 and >20 Gy was 7% and 10%, respectively. This corresponded to a decrease of >2 Gy in the total lung mean dose and of 10% in the risk of radiation pneumonitis. The volumes of the heart and esophagus irradiated to >40-50 Gy and normal thoracic tissue volume irradiated to >10-40 Gy were reduced using the IMRT plans. A marginal increase occurred in the spinal cord maximal dose and lung volume >5 Gy in the IMRT plans, which could be have resulted from the significant increase in monitor units and thus leakage dose in IMRT.

CONCLUSION

IMRT planning significantly improved target coverage and reduced the volume of normal lung irradiated above low doses. The spread of low doses to normal tissues can be controlled in IMRT with appropriately selected planning parameters. The dosimetric benefits of IMRT for advanced-stage non-small-cell lung cancer must be evaluated further in clinical trials.

[New radiotherapy techniques for non-small-cell lung cancer]

Lung cancer is one of the most difficult challenges for radiotherapy. Problems include ballistic targeting compromised by respiratory movements, poor tolerance of neighboring healthy tissues and difficult dosimetry due to the heterogeneous nature of the thoracic tIssues. New perspectives are offered by recent developments allowing a more comprehensive approach to thoracic radiotherapy integrating new advances in imaging techniques, contention, dosimetry, and treatment devices. Two techniques are particularly promising: conformal radiotherapy and respiration-gated radiotherapy. Conformal radiotherapy, a three-dimensional conformal mode of irradiation with or without intensity modulation, is designed to achieve high-precision dose delivery by integrating advanced imaging techniques into the irradiation protocol. These tools are used to optimize irradiation of target Volumes and avoid recurrence while sparing as much as possible healthy tissues. If healthy tissue can be correctly protected, increased doses can be delivered to the target tumor. Respiration-gated techniques offer promising prospects for the treatment of tumors which are displaced by respiratory movements. These techniques allow better adaptation of the irradiation fields to the target tumor and better protection of healthy tissues (lung, heart...). These new approaches are now routine practices in many centers. Early results have been very promising. We describe here the currently available techniques for thoracic radiotherapy.

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.

A survey of intensity-modulated radiation therapy use in the United States

BACKGROUND

The objective of this study was to assess the current level of intensity-modulated radiation therapy (IMRT) use in the United States.

METHODS

Three-hundred thirty-three randomly selected radiation oncologists were sent a 13-question survey regarding IMRT use. IMRT users were asked about the number of patients and sites treated, their reasons for adopting IMRT, and future plans for its use. Physicians who did not use IMRT were asked about their reasons for not using IMRT; whether they intended to adopt it in the future; and, if so, their reasons.

RESULTS

One-hundred sixty-eight responses (50.5%) were received. Fifty-four respondents (32.1%) stated that they currently used IMRT. Most IMRT users (79.6%) had adopted IMRT since 2000. Academic physicians were more likely to use IMRT (P = 0.003) compared with private practitioners. The percent of physicians using IMRT in practices comprised of 1 physician, 2-4 physicians, or > 4 physicians were 15.4%, 28.4%, and 44.2%, respectively (P = 0.02). The most common sites treated were head and neck malignancies and genitourinary tumors. Of the 114 IMRT nonusers, 96.5% planned to use IMRT in the future, with 91.8% planning to use IMRT within 3 years. Among IMRT nonusers, the most common reason cited for not using IMRT was lack of necessary equipment. The most common reasons for adopting IMRT (users) or wanting to adopt IMRT (nonusers) were to improve delivery of conventional doses and to escalate dose.

CONCLUSIONS

Approximately one-third of radiation oncologists in the United States use IMRT. However, this number appears to be growing rapidly. Efforts to ensure the safe and appropriate application of this new technology are warranted.

Can errors in reconstructing pre-chemotherapy target volumes contribute to the inferiority of sequential chemoradiation in stage III non-small cell lung cancer (NSCLC)?

Concurrent chemo-radiotherapy (CT-RT) has been shown to be superior to sequential CT-RT for stage III non-small cell lung cancer (NSCLC). Pre-chemotherapy gross tumor volumes (GTV) are commonly contoured for sequential CT-RT and, as significant inter-clinician variability exists in defining GTV's for lung cancer, we postulated that the poorer local control observed with sequential CT-RT may partly be due to the larger errors in defining GTV after chemotherapy-induced tumor regression. Pre-and post-chemotherapy CT scans for RT planning (RTP) were performed in ten patients who received induction chemotherapy for NSCLC. Image registration of pre- and post-chemotherapy RTP scans was performed for all patients. GTV's were first contoured in the conventional manner by two clinicians, i.e. by visual reconstruction from hard copies of the pre-chemotherapy diagnostic CT scans ('GTV-visual'). A 'GTV-match' was then contoured after image-registration, and the 'gold standard' volume was considered to be the overlap of the 'GTV-match' generated by both clinicians. The 'GTV-match' was on average 31-40% larger than 'GTV-visual'. The mean percentage of the 'gold standard', which was not covered by the 'GTV-visual' was similar for both clinicians, i.e. 26.3+/-12.5 and 28.0+/-15.0%. The inter-clinician agreement in contouring improved after image registration. These data suggest that conventional visual contouring of pre-chemotherapy GTV's may fail to treat the actual pre-chemotherapy tumor volume, and thus confound studies evaluating optimal sequencing of chemo-radiotherapy in NSCLC.

Can elective nodal irradiation be omitted in stage III non-small-cell lung cancer? Analysis of recurrences in a phase II study of induction chemotherapy and involved-field radiotherapy

PURPOSE

To establish the recurrence patterns when elective mediastinal irradiation was omitted, patients with Stage III non-small-cell lung cancer were treated with sequential chemotherapy (CHT) and involved-field radiotherapy (RT).

METHODS AND MATERIALS

Fifty patients were treated with either two or four cycles of induction CHT, followed by once-daily involved-field RT to 70 Gy, delivered using three-dimensional treatment planning. The contoured gross tumor volume consisted of the pre-CHT tumor volume and nodes with a short-axis diameter of > or = 1 cm. Patients were reevaluated at 3 and 6 months after RT using bronchoscopy and chest CT. Elective nodal failure was defined as recurrence in the regional nodes outside the clinical target volume, in the absence of in-field failure.

RESULTS

Of 43 patients who received doses > or = 50 Gy, 35% were disease free at last follow-up; in-field recurrences developed in 27% (of whom 16% had exclusively in-field recurrences); 18% had distant metastases exclusively. No elective nodal failure was observed. The median actuarial overall survival was 18 months (95% confidence interval 14-22) and the median progression-free survival was 12 months (95% confidence interval 6-18).

CONCLUSION

Omitting elective mediastinal irradiation did not result in isolated nodal failure. Future studies of concurrent CHT and RT for Stage III non-small-cell lung cancer should use involved-field RT to limit toxicity.

[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.

What margins are necessary for incorporating mediastinal nodal mobility into involved-field radiotherapy for lung cancer?

PURPOSE

The mobility of mediastinal nodes was studied on multiple CT scans of the thorax from patients with non-small-cell lung cancer.

PATIENTS AND METHODS

A total of 10 enlarged mediastinal nodes/masses were identified in 8 patients with non-small-cell lung cancer. Nodal locations were classified using the Naruke/ATS-LCSG system, and between 3 and 6 scans were available for each site. The CT data sets were coregistered, and the contoured nodes were automatically projected onto the initial planning CT scan. An encompassing nodal volume (ENV) of all contours of a particular node was manually contoured on all scans. Individual nodal volumes were expanded in three dimensions to establish additional margins required to encompass the ENV.

RESULTS

The mean volume of nodes studied ranged from 0.8 to 23.2 cc. The addition to individual nodes of a margin of 5 mm was found to result in a mean ENV coverage of >or=95% at all sites. For individual nodes at locations N4R, N5, and N6, however, the coverage ranged from 87.8% to 92.6%.

CONCLUSION

The addition of a margin of 5 mm to individual mediastinal nodes seems to be adequate to account for variations in both contouring and mobility.