Three-dimensional radiation treatment planning study for patients with carcinoma of the lung

Janus ACSP Nanoparticle for Synergistic Chemodynamic Therapy and Radiosensitization

Protective autophagy and DNA damage repair lead to tumor radio-resistance. Some hypoxic tumors exhibit a low radiation energy absorption coefficient in radiation therapy. High doses of X-rays may lead to side effects in the surrounding normal tissues. In order to overcome the radio-resistance and improve the efficacy of radiotherapy based on the characteristics of the tumor microenvironment, the development of radiosensitizers has attracted much attention. In this study, a Janus ACSP nanoparticle (NP) was developed for chemodynamic therapy and radiosensitization. The reactive oxygen species generated by the Fenton-like reaction regulated the distribution of cell cycles from a radioresistant phase to a radio-sensitive phase. The high-Z element, Au, enhanced the production of hydroxyl radicals (•OH) under X-ray radiation, promoting DNA damage and cell apoptosis. The NP delayed DNA damage repair by interfering with certain proteins involved in the DNA repair signaling pathway. In vivo experiments demonstrated that the combination of the copper-ion-based Fenton-like reaction and low-dose X-ray radiation enhanced the effectiveness of radiotherapy, providing a novel approach for synergistic chemodynamic and radiosensitization therapy. This study provides valuable insights and strategies for the development and application of NPs in cancer treatment.

Impact of Interobserver Variability in Manual Segmentation of Non-Small Cell Lung Cancer (NSCLC) Applying Low-Rank Radiomic Representation on Computed Tomography

Simple Summary

Discovery of predictive and prognostic radiomic features in cancer is currently of great interest to the radiologic and oncologic community. Tumor phenotypic and prognostic information can be obtained by extracting features on tumor segmentations, and it is typically imaging analysts, physician trainees, and attending physicians who provide these labeled datasets for analysis. The potential impact of level and type of specialty training on interobserver variability in manual segmentation of NSCLC was examined. Although there was some variability in segmentation between readers, the subsequently extracted radiomic features were overall well correlated. High fidelity radiomic feature extraction relies on accurate feature extraction from imaging that produce robust prognostic and predictive radiomic NSCLC biomarkers. This study concludes that this goal can be obtained using segmenters of different levels of training and clinical experience.

Abstract

This study tackles interobserver variability with respect to specialty training in manual segmentation of non-small cell lung cancer (NSCLC). Four readers included for segmentation are: a data scientist (BY), a medical student (LS), a radiology trainee (MH), and a specialty-trained radiologist (SK) for a total of 293 patients from two publicly available databases. Sørensen–Dice (SD) coefficients and low rank Pearson correlation coefficients (CC) of 429 radiomics were calculated to assess interobserver variability. Cox proportional hazard (CPH) models and Kaplan-Meier (KM) curves of overall survival (OS) prediction for each dataset were also generated. SD and CC for segmentations demonstrated high similarities, yielding, SD: 0.79 and CC: 0.92 (BY-SK), SD: 0.81 and CC: 0.83 (LS-SK), and SD: 0.84 and CC: 0.91 (MH-SK) in average for both databases, respectively. OS through the maximal CPH model for the two datasets yielded c-statistics of 0.7 (95% CI) and 0.69 (95% CI), while adding radiomic and clinical variables (sex, stage/morphological status, and histology) together. KM curves also showed significant discrimination between high- and low-risk patients (p-value < 0.005). This supports that readers’ level of training and clinical experience may not significantly influence the ability to extract accurate radiomic features for NSCLC on CT. This potentially allows flexibility in the training required to produce robust prognostic imaging biomarkers for potential clinical translation.

Size and Predictive Factors of Microscopic Tumor Extension in Locally Advanced Non-Small Cell Lung Cancer

PURPOSE

Radiation therapy for locally advanced non-small cell lung cancer (NSCLC) should treat the whole tumor, including its microscopic extensions, and protect adjacent organs at risk as much as possible. The aim of our study is to evaluate the size of microscopic tumor extension (MEmax) in NSCLC, and search for potential predictive factors.

METHODS AND MATERIALS

We retrospectively selected 70 patients treated with postoperative radiation therapy for a NSCLC with N2 nodal status, then 34 additional patients operated for a squamous cell lung cancer with N1 or N2 nodal status. On the digitized slides originating from the resected tumors of these 104 patients, we outlined the border of the tumor, as seen with the naked eye. We then searched for microscopic tumor extension outside of these borders with a magnification as high as 40 × and measured the maximum size of MEmax.

RESULTS

The median MEmax in the whole cohort was 0.85 mm (0-9.95). The MEmax was <5.3 mm in 95% of adenocarcinomas (6.5 mm in the subgroup without neoadjuvant chemotherapy) and <3.5 mm in 95% of squamous cell carcinomas (3.7 mm in the subgroup without neoadjuvant chemotherapy). After multivariate analysis, the factors associated with the size of MEmax were vascular invasion (P = .0002), histologic type, with a wider MEmax for adenocarcinomas in comparison with squamous cell carcinomas (P = .002), tumor size, which was inversely related with the size of MEmax (P = .024), and high blood pressure (P = .03). Macroscopic histologic tumor size was well correlated with both radiologic tumor size on a mediastinal setting computed tomography (correlation coefficient of 0.845) and on a parenchymal setting computed tomography (correlation coefficient of 0.836).

CONCLUSIONS

The clinical target volume margin, accounting for microscopic tumoral extension, could be reduced to 7 mm for adenocarcinomas and 4 mm for squamous cell carcinomas.

Current challenges in clinical target volume definition: tumour margins and microscopic extensions

Determination of optimal clinical target volume (CTV) margins around gross tumour volume (GTV) for modern radiotherapy techniques, requiring more precise target definitions, is controversial and complex. Tumour localisation has been greatly improved using molecular imaging integrated with conventional imaging techniques. However, the exact incidence and extent of microscopic disease, to be encompassed by CTV, cannot be visualised by any techniques developed to date and remain uncertain. As a result, the CTV is generally determined by clinicians based on their experience and patients' histopathological data. In this article we review histopathological studies addressing the extent of subclinical disease and its possible correlation with tumour characteristics in various tumour sites. The data have been tabulated to facilitate a comparison between proposed margins by different investigations and with current margins generally accepted for each tumour site. It is concluded that there is a need for further studies to reach a consensus on the optimal CTV pertaining to each tumour site.

Extracting fuzzy classification rules from texture segmented HRCT lung images

Automatic tools for detection and identification of lung and lesion from high-resolution CT (HRCT) are becoming increasingly important both for diagnosis and for delivering high-precision radiation therapy. However, development of robust and interpretable classifiers still presents a challenge especially in case of non-small cell lung carcinoma (NSCLC) patients. In this paper, we have attempted to devise such a classifier by extracting fuzzy rules from texture segmented regions from HRCT images of NSCLC patients. A fuzzy inference system (FIS) has been constructed starting from a feature extraction procedure applied on overlapping regions from the same organs and deriving simple if-then rules so that more linguistically interpretable decisions can be implemented. The proposed method has been tested on 138 regions extracted from CT scan images acquired from patients with lung cancer. Assuming two classes of tissues C1 (healthy tissues) and C2 (lesion) as negative and positive, respectively; preliminary results report an AUC = 0.98 for lesions and AUC = 0.93 for healthy tissue, with an optimal operating condition related to sensitivity = 0.96, and specificity = 0.98 for lesions and sensitivity 0.99, and specificity = 0.94 for healthy tissue. Finally, the following results have been obtained: false-negative rate (FNR) = 6 % (C1), FNR = 2 % (C2), false-positive rate (FPR) = 4 % (C1), FPR = 3 % (C2), true-positive rate (TPR) = 94 %, (C1) and TPR = 98 % (C2).

Conformal radiotherapy for lung cancer: interobservers' variability in the definition of gross tumor volume between radiologists and radiotherapists

Background

Conformal external radiotherapy aims to improve tumor control by boosting tumor dose, reducing morbidity and sparing healthy tissues. To meet this objective careful visualization of the tumor and adjacent areas is required. However, one of the major issues to be solved in this context is the volumetric definition of the targets. This study proposes to compare the gross volume of lung tumors as delineated by specialized radiologists and radiotherapists of a cancer center.

Methods

Chest CT scans of a total of 23 patients all with non-small cell lung cancer, not submitted to surgery, eligible and referred to conformal radiotherapy on the Hospital A. C. Camargo (São Paulo, Brazil), during the year 2004 were analyzed. All cases were delineated by 2 radiologists and 2 radiotherapists. Only the gross tumor volume and the enlarged lymph nodes were delineated. As such, four gross tumor volumes were achieved for each one of the 23 patients.

Results

There was a significant positive correlation between the 2 measurements (among the radiotherapists, radiologists and intra-class) and there was randomness in the distribution of data within the constructed confidence interval.

Conclusion

There were no significant differences in the definition of gross tumor volume between radiologists and radiotherapists.

Continuous hyperfractionated accelerated radiation therapy week-end less in combination with neoadjuvant chemotherapy for the treatment of stage III non-small-cell lung cancer

PURPOSE

Current treatment for unresectable stage III lung cancer includes standard radiotherapy with chemotherapy. Continuous hyperfractionated radiotherapy has been shown to be more effective than standard radiotherapy but may be associated with increased toxicity. In this study, we evaluated the feasibility and outcomes of patients treated with a hyperfractionated accelerated regimen in combination with neoadjuvant chemotherapy.

METHODS AND MATERIALS

We prospectively studied 61 consecutive patients with unresectable stage III non-small-cell lung cancer. All patients received three dimensional conformal radiotherapy using three daily fractions of 1.5 Gy to a total dose of 54-60 Gy omitting elective mediastinal irradiation. Approximately two-thirds of the patients also received platinum-based neoadjuvant chemotherapy. The primary outcome was locoregional disease-free survival. Secondary analyses were performed to assess tolerability, response rates, and overall and disease-free survival among study participants.

RESULTS

Overall, 56% of patients had a complete response. Locoregional recurrence was observed in 55% of patients with only a 3% rate of dissemination to non-irradiated mediastinal lymph nodes. Median locoregional disease-free survival, disease-free survival, and overall survival were 16 months (95% CI: 12-20), 15 months (95% CI: 12-18), and 19 months (95% CI: 15-30), respectively. Additionally, no episodes of severe toxicity were reported among study participants. Poor performance status and radiation response were independent predictors of survival.

CONCLUSIONS

This study suggests that conformal three-dimensional hyperfractionated accelerated radiotherapy omitting elective node irradiation can be used in combination with neoadjuvant chemotherapy to treat patients with stage III lung cancer. Future studies should compare this approach with the standard treatments for patients with stage III lung cancer.

Change in dose distribution of three-dimensional conformal radiotherapy during treatment for lung tumor

PURPOSE

We investigated the changes in dose distribution of three-dimensional conformal radiotherapy (3D CRT) during lung tumor treatment.

MATERIALS AND METHODS

Ten patients with non-small cell lung cancer who had undergone planning for radical radiotherapy were selected for study. Computed tomography (CT) examination was performed at two time intervals during the course of conformal radiotherapy: t0 Gy at the time of planning and t40 Gy at 40 Gy of treatment. We transferred all the planned beam data at t0 Gy to each t40 Gy CT image. The isodose distribution was recalculated at time t40 Gy for the same beam characteristics. Variations in volumes and dose-volume histograms (DVHs) were analyzed and compared for lung, gross target volume (GTV), and planning target volumes (PTV) between t0 Gy and t40 Gy. A paired t-test was performed to compare the DVH between t0 Gy and t40 Gy.

RESULTS

The mean minimum doses for t40 y GTV, and PTV were lower than t0 y. However, there was no significant difference between t0 Gy and t40 Gy (p=0.493, 0.378, respectively). There was a patient whose minimum doses of GTV and PTV were decreased and who had notable improvement of lobar atelectasis after 40 Gy of radiotherapy. Comparison of the percent volume of received dose exceeding 20 Gy (V20) and the mean dose for the total lung revealed that t40 Gy was larger than to Gy (p=0.013, 0.012).

CONCLUSION

Incorporation of the time factor into 3D treatment planning is mandatory for frequent reiteration of treatment planning during treatment periods. Clearly, more work in this area should be considered.

Multivariate analysis of survival, local control, and time to distant metastases in patients with unresectable non-small-cell lung carcinoma treated with 3-dimensional conformal radiation therapy with or without concurrent chemotherapy

BACKGROUND

Three-dimensional (3D) conformal radiation therapy (CRT) and chemotherapy have recently improved lung cancer management.

PATIENTS AND METHODS

We reviewed outcomes in 68 patients with unresectable stage I-III non-small-cell lung cancer. Treatment consisted of 3D CRT alone or with concurrent chemotherapy (CCR).

RESULTS

Concurrent chemotherapy improved survival, to a median of 17 months +/- 4.9 months, compared with 8 months+/- 4.1 months for the radiation therapy (RT) alone group (P=0.0347). The 2- and 5-year survival rates were 40.3%+/-7.7% and 14.1%+/-6.4%, respectively, with CCR, compared with 19.6%+/- 9.6% and 0, respectively, for RT alone. In a subgroup analysis for age > 65, patients who received CCR (n=20) had significantly improved survival and local control (P=0.005 and P=0.0286, respectively). Acute esophageal toxicity Radiation Therapy Oncology Group grade >or= 3 was significantly higher in the CCR group and correlated with the RT dose (19% in CCR vs. 0 in RT, P=0.0234; P=0.050). The overall incidences of esophageal and pulmonary toxicity grade >or= 3 were 20.6% and 5.9%, respectively.

CONCLUSION

Our study confirms that CCR is associated with improved survival over RT alone, with a tolerable increase in acute toxicity.

Imaging of the Patient with Non–Small Cell Lung Cancer

Lung cancer is the most common type of cancer and is the leading cause of cancer deaths in the United States for both men and women. Even though the 5-year survival rate of patients with lung cancer remains dismal at 14% for all cancer stages, treatments are improving and newer agents for lung cancer appear promising. Therefore, an accurate assessment of the extent of disease is critical to determine whether the patient is treated with surgical resection, radiation therapy, chemotherapy, or a combination of these modalities. Radiologic imaging plays an important role in the staging evaluation of the patient; however, radiologists need to be aware that there are also important differences in what each specialist needs from imaging to provide appropriate treatment. This article reviews the role of imaging in patients with non-small cell lung cancer, with an emphasis on the radiologic imaging findings relevant for each specialty.

Treatment-related esophagitis

Current therapeutic approaches for lung cancer favor treatment intensification, with the presumption that dose-intense chemotherapy regimens and/or higher radiation therapy (RT) doses or novel fractionation schemes will result in increased patient survival. Also, the trend for non-operative therapy has favored concurrent over sequential regimens. The incidence of severe acute esophagitis in patients treated for lung cancer with standard (once daily) RT alone is 1.3%, and induction chemotherapy increases the risk of severe acute esophagitis slightly over that of standard RT alone. In contrast, a strong radiosensitizing effect of chemotherapy given concurrently with standard thoracic RT (chemoRT) is associated with an incidence of severe esophagitis of 14% to 49%. Acute esophagitis may be severe and disabling, and result in hospitalization, placement of a feeding tube in the stomach or intravenous feedings, and steady supportive care. Also, RT may need to be halted temporarily to allow for healing of the esophageal lining; treatment breaks in turn decrease survival of patients with unresectable lung cancer. Therefore, esophagitis as a dose-limiting toxicity of chemoRT may have a direct impact on tumor control and survival. Aggressive types of RT fractionation have also been associated with worsening esophagitis grades and duration. Moreover, it is commonly assumed in the radiation oncology clinic that the longer the length of the esophagus segment included in the RT field the higher the probability of esophageal toxicity, although differing opinions are commonly expressed. Recent advances in 3-dimensional conformal RT allow a unique chance to gain volumetric data pertaining to organ damage rather than rely on older estimates based on organ length (eg, esophagus) or portion (ie, lung, spinal cord). The Radiation Therapy Oncology Group (RTOG) conducted a large phase III, randomized study RTOG 98-01 examining chemoRT with or without the amifostine (Ethyol; MedImmune, Inc, Gaithersburg, MD), a cyto- and radioprotectant in locally advanced non-small cell lung cancer (n = 243). While amifostine did not significantly reduce severe esophagitis based on National Cancer Institute Common Toxicity Criteria and weekly physician dysphagia logs, swallowing dysfunction over time (based on patient diaries, the equivalent of Esophagitis Index) was significantly lower in the amifostine arm ( P = .03). Therefore, significant progress has been accomplished in our understanding of the basis of esophageal injury resulting from thoracic RT, and future effort may find other effective strategies to either minimize or eliminate esophagitis.

Imaging of non-small cell lung cancer

Radiologic evaluation is an important component of the clinical staging evaluation of lung cancer and can greatly influence whether the patient is treated with surgical resection, radiation therapy, chemotherapy, or a combination of these modalities. In addition to staging, the radiologic evaluation of the patient undergoing treatment and subsequent follow-up is important to the clinician for assessing treatment effects and complications. This article discusses the imaging of patients with non-small cell lung cancer and its use in management of these patients.

Comparison of three IMRT inverse planning techniques that allow for partial esophagus sparing in patients receiving thoracic radiation therapy for lung cancer

The purpose of this study is to compare 3 intensity-modulated radiation therapy (IMRT) inverse treatment planning techniques as applied to locally-advanced lung cancer. This study evaluates whether sufficient radiotherapy (RT) dose is given for durable control of tumors while sparing a portion of the esophagus, and whether large number of segments and monitor units are required. We selected 5 cases of locally-advanced lung cancer with large central tumor, abutting the esophagus. To ensure that no more than half of the esophagus circumference at any level received the specified dose limit, it was divided into disk-like sections and dose limits were imposed on each. Two sets of dose objectives were specified for tumor and other critical structures for standard dose RT and for dose escalation RT. Plans were generated using an aperture-based inverse planning (ABIP) technique with the Cimmino algorithm for optimization. Beamlet-based inverse treatment planning was carried out with a commercial simulated annealing package (CORVUS) and with an in-house system that used the Cimmino projection algorithm (CIMM). For 3 of the 5 cases, results met all of the constraints from the 3 techniques for the 2 sets of dose objectives. The CORVUS system without delivery efficiency consideration required the most segments and monitor units. The CIMM system reduced the number while the ABIP techniques showed a further reduction, although for one of the cases, a solution was not readily obtained using the ABIP technique for dose escalation objectives.

Segmentation of IMRT plans for radical lung radiotherapy delivery with the step-and-shoot technique

The purpose of this work was to determine a segmentation protocol for the treatment of localized non-small-cell lung cancer (NSCLC) with intensity-modulated radiotherapy (IMRT) that is as effective as possible while practically simple and hence robust to known practical inaccuracies. This study focused on the stratification of continuous profiles into a discrete number of intensity levels. The selection of the segmentation parameters for the delivery of the fluence profiles using multiple static fields has been considered. Five-field equispaced IMRT treatment plans of five patients with NSCLC were selected. The study comprised nine treatment plans for each patient, starting from a conformal plan, optimizing it for IMRT and then segmenting it utilizing different numbers of segments in each case and optimizing for segment weights separately. A conformal plan, optimized for beam directions, collimator and wedge angles, was also used for comparison with the IMRT plans, so as to consider the best coplanar conformal case. A dose objective for the PTV and the organs-at-risk plus a constraint for the spinal cord were set for all inverse plans. All stages were compared with the aid of dose-volume histograms, dose distributions at the plane of the isocenter, intensity maps for key beams and plots of PTV homogeneity and overall conformality versus complexity. The unsegmented IMRT plans gave the best results but cannot be realized in practice with an MLC. They were best approximated by plans that needed 106-167 segments to deliver, but did not deteriorate significantly when approximated by plans which required 26-40 segments in total. All segmented IMRT plans gave a better lung sparing than the conformal plans, indicating that the deterioration of IMRT plans following segmentation is not equivalent to that of unmodulated, conformal plans. However, optimized conformal plans have the potential to approach the lung sparing achieved by segmented IMRT plans. Among the IMRT situations examined, five-field treatment plans for the lung, utilizing a maximum of 40 segments in total, have proven to give a good approximation of the IMRT plans with continuous modulation.

Geometrically based optimization for extracranial radiosurgery

For static beam conformal intracranial radiosurgery, geometry of the beam arrangement dominates overall dose distribution. Maximizing beam separation in three dimensions decreases beam overlap, thus maximizing dose conformality and gradient outside of the target volume. Webb proposed arrangements of isotropically convergent beams that could be used as the starting point for a radiotherapy optimization process. We have developed an extracranial radiosurgery optimization method by extending Webb's isotropic beam arrangements to deliverable beam arrangements. This method uses an arrangement of N maximally separated converging vectors within the space available for beam delivery. Each bouquet of isotropic beam vectors is generated by a random sampling process that iteratively maximizes beam separation. Next, beam arrangement is optimized for critical structure avoidance while maintaining minimal overlap between beam entrance and exit pathways. This geometrically optimized beam set can then be used as a template for either conformal beam or intensity modulated extracranial radiosurgery. Preliminary results suggest that using this technique with conformal beam planning provides high plan conformality, a steep dose gradient outside of the tumour volume and acceptable critical structure avoidance in the majority of clinical cases.

Radioprotective effect of amifostine in radiation pneumonitis

Amifostine (Ethyol, WR-2721; MedImmune, Inc, Gaithersburg, MD) is a member of a sulfhydryl-containing class of compounds that protects normal tissue and organs against ionizing radiation damage by scavenging radiation-induced radicals. The goal of this study was to assess the preclinical and clinical data on the protective effect of amifostine in normal organs and tissue. The current literature was reviewed and assessed for progress in the pathogenesis of radiation-induced pulmonary injury. Preclinical and clinical data on the protective effect of amifostine in radiation-induced lung and esophageal injuries were also critically assessed. Significant progress has been made in understanding the pathogenesis of radiation pneumonitis. Preclinical studies have shown strong evidence of the protective effect of amifostine in radiation-induced toxicities in rodents and monkeys. However, available clinical data are not conclusive in showing the protective effect of amifostine in radiation pneumonitis and esophagitis. Amifostine has been well tolerated with a low incidence of toxicities, which included nausea and vomiting (3% to 5%) and transient hypotension during intravenous infusion (7%). Preclinical data are promising for amifostine in protecting thoracic organs from radiation-induced toxicities. Studies measuring the magnitude of gain in tumor control and survival as a result of the enhanced protective effect of amifostine on normal tissue over that of tumor tissue are lacking. Such data would help in designing new approaches to maximize outcome. Additional well-designed phase III studies are necessary to confirm the clinical benefit of amifostine in minimizing radiation- and chemoradiation-related toxicities in patients with lung cancer.

Normal-tissue toxicities of thoracic radiation therapy: esophagus, lung, and spinal cord as organs at risk

The evolution of therapeutic approaches for lung cancer illustrates the trend for treatment intensification, with hopes that dose-intense chemotherapy regimens, higher radiation therapy (RT) doses, or novel fractionation schemes will result in prolongation of survival. Current chemotherapy- and RT-intense regimens may not be intensified further without addressing dose-limiting toxicities such as esophagitis. It is important to understand factors pre-disposing to esophagitis so that strategies to minimize its severity can be investigated. Pulmonary complications such as pneumonitis and fibrosis from RT (with or without chemotherapy) are dose and volume dependent. Methods to better identify the target tissues and improved RT-delivery systems may facilitate increasing target doses or reducing doses to adjacent normal tissues. Biologic predictors may allow clinicians in the future to individualize RT treatment based on a patient's toxicity risk profile. Radiation myelopathy is still the most feared radiation complication of lung cancer treatment. The authors address the known parameters that influence the incidence of thoracic radiation myelopathy and the putative factors that could be considered when a clinician may be required to push the spinal cord dose in favor of tumor control.

A systematic overview of radiation therapy effects in non-small cell lung cancer

A systematic review of radiation therapy trials in several tumour types was performed by The Swedish Council of Technology Assessment in Health Care (SBU). The procedures for evaluation of the scientific literature are described separately (Acta Oncol 2003; 42: 357-365). This synthesis of the literature on radiation therapy for non-small cell lung cancer (NSCLC) is based on data from 4 meta-analyses and 31 randomized trials. Moreover, data from 12 prospective studies, 12 retrospective studies and 6 other articles were used. In total, 65 scientific articles are included, involving 18 310 patients. The results were compared with those of a similar overview from 1996 including 28 172 patients. The conclusions reached can be summarized as follows: Extensive clinical experience indicates that radiotherapy for medically inoperable patients or patients refusing surgery with NSCLC stage I/II prolongs survival, 15 -20% of these patients reaching long-term (5-year) survival. However, no randomized trials have addressed this issue. There is strong evidence that postoperative radiotherapy in radically resected stage I/II NSCLC does not prolong survival compared with observation alone. There is some evidence that continuous hyperfractionated accelerated radiotherapy (CHART) is associated with increased survival compared to conventional radiotherapy in locally advanced NSCLC and also in medically unfit patients with stage I/II NSCLC. However, the benefit is limited to squamous cell histology. There is strong evidence that combined modality treatment with platinum-based chemotherapy and radiotherapy, either neoadjuvant or concomitant, is superior to radiotherapy alone in terms of survival in locally advanced unresectable NSCLC and should be the standard of care in patients with good performance status. There is some evidence that concomitant chemo-radiotherapy is associated with increased survival compared with sequential chemo-radiotherapy, albeit at the price of increased toxicity Comment: Combined chemo-radiotherapy of primary non-resectable stage III NSCLC followed by surgery in responders lacks evidence from prospective randomized trials and cannot be recommended for routine use. There is strong evidence that radiotherapy can palliate symptoms associated with the intrathoracic tumour burden. There is some evidence that two large fractions may be as effective as conventional schedules consisting of 10-13 smaller fractions in terms of palliation of symptoms. There is some evidence that endobronchial brachytherapy for palliation of symptoms associated with endobronchial tumours is not superior to external beam radiotherapy.

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

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

[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.

Radiotherapy alone in technically operable, medically inoperable, early-stage (I/II) non-small-cell lung cancer

PURPOSE

To investigate the effectiveness of high-dose, curative radiotherapy (RT) given alone in technically operable, but medically inoperable, patients with early-stage (I-II) non-small-cell lung cancer (NSCLC).

METHODS AND MATERIALS

Computerized and manual searches were done to identify published reports dealing with curative RT for NSCLC. Relevant studies were identified and the information provided therein was extracted regarding patient and treatment characteristics, treatment outcome, and various pretreatment and treatment-related factors influencing outcome, as well as toxicity and quality-of-life issues.

RESULTS

Although a large variation of pretreatment and treatment characteristics was noted in the available studies, a median survival time of >30 months and a 5-year survival rate of up to 30% had been achieved. Accumulated experience seems to suggest that doses of at least 65 Gy with standard fractionation, or its equivalent when altered fractionation is used, are necessary for control of NSCLC. Smaller tumors seem to have a favorable prognosis, and the issue of elective nodal RT continues to be controversial. Analyses of patterns of failure have clearly identified local failure as the predominant pattern. Although a number of potential pretreatment patient- and tumor-related prognostic factors have been examined, none has been shown to clearly influence survival. Toxicity was usually low, but very high doses (e.g., 80 Gy) given with a conventional approach may carry a risk of an excessive rate of side effects.

CONCLUSION

High-dose, curative RT is an effective treatment modality in technically operable, but medically inoperable, patients with early-stage NSCLC.

Methodological issues in radiation dose-volume outcome analyses: summary of a joint AAPM/NIH workshop

This report represents a summary of presentations at a joint workshop of the National Institutes of Health and the American Association of Physicists in Medicine (AAPM). Current methodological issues in dose-volume modeling are addressed here from several different perspectives. Areas of emphasis include (a) basic modeling issues including the equivalent uniform dose framework and the bootstrap method, (b) issues in the valid use of statistics, including the need for meta-analysis, (c) issues in dealing with organ deformation and its effects on treatment response, (d) evidence for volume effects for rectal complications, (e) the use of volume effect data in liver and lung as a basis for dose escalation studies, and (f) implications of uncertainties in volume effect knowledge on optimized treatment planning. Taken together, these approaches to studying volume effects describe many implications for the development and use of this information in radiation oncology practice. Areas of significant interest for further research include the meta-analysis of clinical data; interinstitutional pooled data analyses of volume effects; analyses of the uncertainties in outcome prediction models, minimal parameter number outcome models for ranking treatment plans (e.g., equivalent uniform dose); incorporation of the effect of motion in the outcome prediction; dose-escalation/isorisk protocols based on outcome models; the use of functional imaging to study radioresponse; and the need for further small animal tumor control probability/normal tissue complication probability studies.

Three-dimensional conformal radiotherapy for lung cancer: promises and pitfalls

Lung cancer represents a major source of morbidity and mortality. Despite recent advances, long-term survival remains elusive in most patients with locally advanced cancer. A substantial proportion of these patients experience a relapse at the original site of disease within the thorax, making radiotherapy an important component of treatment. Of several approaches investigated to improve the therapeutic ratio in radiotherapy, three-dimensional conformal radiotherapy holds the most promise, primarily because it allows higher doses to be delivered to the target by improved shaping of radiation portals and conformal avoidance of normal structures. The rationale and evolution of this technology and its potential pitfalls are presented in this review.

The application of a radiotherapy-planning system: consideration from a case of intraoral squamous cell carcinoma that lacked a control

OBJECTIVE

The purpose of this case study was to present an applied example of a radiotherapy-planning system used during the treatment of a malignant tumor in the oral and maxillofacial region.

STUDY DESIGN

The various radiotherapy modalities were performed on a patient with oral squamous cell carcinoma of multiple metachronous recurrences. Estimated radiation dose-distribution curves for each radiotherapy modality were computed by using a commercially available radiotherapy-planning system. A personal computer was used to make the superimposed radiation dose-distribution curve.

RESULTS

The 3-dimensional dose-distribution curves were determined with the radiotherapy-planning system. In addition, with the use of superimposition of the dose-distribution curves from all sources of radiotherapy, it was possible to estimate regions receiving extremely high radiation dosages. This information serves as a road map to potential postradiation complication sites at follow-up examinations.

CONCLUSION

The radiotherapy-planning system is very useful for the evaluation of a radiotherapy dosage to treat malignant tumors in the oral and maxillofacial region.

Radiation injury of the lung after three-dimensional conformal radiation therapy

OBJECTIVE

The objective of this study is to describe the CT patterns of radiation injury in the lungs of patients who have undergone three-dimensional (3D) conformal radiation therapy (CRT).

MATERIALS AND METHODS

Over a 36-month period, the chest CT scans of 19 patients with non-small cell lung cancer who were treated with 3D CRT were reviewed. CT scans were evaluated for findings of radiation injury (ground-glass opacities, consolidation, bronchiectasis, and volume loss). The presence, extent, and distribution of these findings were reached by consensus.

RESULTS

Radiation pneumonitis limited to a small area immediately around the tumor was present in all patients who were imaged within 3 months after completion of the treatment (n = 7). Radiation-induced fibrosis occurred in all patients (n = 19). Three distinct patterns of fibrosis were consistently present, and these were classified as modified conventional, masslike, and scarlike. Modified conventional fibrosis (consolidation, volume loss, and bronchiectasis similar to, but less extensive than, conventional radiation fibrosis) was seen in five patients. Masslike fibrosis (focal consolidation with traction bronchiectasis limited to the site of the original tumor) was seen in eight patients. Scarlike fibrosis (linear opacity in the region of the original tumor associated with moderate to severe volume loss) was seen in six patients.

CONCLUSION

Three-dimensional conformal radiation therapy results in three patterns of radiation fibrosis that differ from the conventional radiation-induced lung injury. Knowledge of the full spectrum of these manifestations is useful in the correct interpretation of CT scans after 3D CRT.

Update on Results of Multifield Conformal Radiation Therapy of Non—Small-Cell Lung Cancer Using Multileaf Collimated Beams

We evaluated the treatment outcome for 5-field 3-dimensional conformal radiation therapy (3D-CRT) in 46 consecutive patients with unresectable, nonmetastatic non-small-cell lung cancer treated from 1993-2001. Four percent of the patients had stage I tumors, 6% had stage II, 44% had stage IIIA, and 46% had stage IIIB tumors. The median radiation therapy (RT) dose to the gross tumor volume with a median of 467.5 cc (range, 75.0-3073.0 cc) was 6120 cGy (range, 3000-6840 cGy). Thirty-one of 46 patients (67.4%) received combined chemoradiotherapy. Mean follow-up was 13.2 months (range, 3-159 months). Survival for stage III patients was 48.7% +/-9.1% at 1 year and 25.0% +/-8.4% at 2 years, with a median survival of 12.0 months+/-4.4 months. The local control rate for stage III patients was 66.8%+/- 9.4% at 1 year and 28.5%+/- 10.4% at 2 years. Patients who received chemotherapy had better survival (P = 0.0533) and local control (P = 0.0984) compared with patients receiving RT alone. Esophageal toxicity >or= grade 3 was significantly greater in combined chemoradiotherapy patients (29% early, 13% late) compared to the patients receiving RT alone (0% early and late). Pulmonary toxicity (early and late) was limited to grades 1/2 in 24% of patients and early grade 3 in 2% of patients. Chemotherapy appears to improve survival and local control when added to 3D-CRT in this series. The addition of concurrent chemotherapy to RT significantly increased esophageal toxicity (within acceptable levels) and did not effect pulmonary toxicity in this series.

Definition of gross tumor volume in lung cancer: inter-observer variability

BACKGROUND AND PURPOSE

To determine the inter-observer variation in gross tumor volume (GTV) definition in lung cancer, and its clinical relevance.

MATERIALS AND METHODS

Five clinicians involved in lung cancer were asked to define GTV on the planning CT scan of eight patients. Resulting GTVs were compared on the base of geometric volume, dimensions and extensions. Judgement of invasion of lymph node (LN) regions was evaluated using the ATS/LCSG classification of LN. Clinical relevance of the variation was studied through 3D-dosimetry of standard conformal plans: volume of critical organs (heart, lungs, esophagus, spinal cord) irradiated at toxic doses, 95% isodose volumes of GTVs, normal tissue complication probabilities (NTCP) and tumor control probabilities (TCP) were compared for evaluation of observer variability.

RESULTS

Before evaluation of observer variability, critical review of planning CT scan led to up- (two cases) and downstaging (one case) of patients as compared to the respective diagnostic scans. The defined GTVs showed an inter-observer variation with a ratio up to more than 7 between maximum and minimum geometric content. The dimensions of the primary tumor had inter-observer ranges of 4.2 (transversal), 7.9 (cranio-caudal) and 5.4 (antero-posterior) cm. Extreme extensions of the GTVs (left, right, cranial, caudal, anterior and posterior) varied with ranges of 2.8-7.3 cm due to inter-observer variation. After common review, only 63% of involved lymph node regions were delineated by the clinicians (i.e. 37% are false negative). Twenty-two percent of drawn in lymph node regions were accepted to be false positive after review. In the conformal plans, inter-observer ranges of irradiated normal tissue volume were on average 12%, with a maximum of 66%. The probability (in the population of all conformal plans) of irradiating at least 95% of the GTV with at least 95% of the nominal treatment dose decreased from 96 to 88% when swapping the matched GTV with an unmatched one. The average (over all patients) inter-observer range in NTCP varied from 5% (spinal cord) to 20% (ipsilateral lung), whereas the maximal ranges amounted 16% (spinal cord) to 45% (heart). The average TCP amounted 51% with an average range of 2% (maximally 5%) in case of matched GTVs. These values shifted to 42% (average TCP) with an average range of 14% (maximally 31%) when defining unmatched GTVs. Four groups of causes are suggested for the large inter-observer variation: (1) problems of methodology; (2) impossible differentiation between pathologic structures and tumor; or (3) between normal structures and tumor, and (4); lack of knowledge. Only the minority of these can be resolved objectively. For most of the causal factors agreements have to be made between clinicians, intra- and inter-departmentally. Some of the factors will never be unequivocally solved.

CONCLUSIONS

GTV definition in lung cancer is one of the cornerstones in quality assurance of radiotherapy. The large inter-observer variation in GTV definition jeopardizes comparison between clinicians, institutes and treatments.

Randomized phase III trial of radiation treatment +/- amifostine in patients with advanced-stage lung cancer

PURPOSE

This multicenter trial investigated whether daily pretreatment with amifostine (A) could reduce the incidence of acute and late lung toxicity and esophagitis without affecting antitumor efficacy of radiation in advanced lung cancer.

PATIENTS AND METHODS

Radiotherapy (XRT) patients (n = 146) received a daily fraction of 2 Gy/5 days/week to a total of 55-60 Gy +/- amifostine 340 mg/m(2) administered daily 15 min before irradiation. Acute and late toxicities were graded from 0 to 4 according to the Radiation Therapy Oncology Group/European Organization for the Research and Treatment of Cancer system.

RESULTS

Ninety-seven patients were evaluated 2 months post-XRT for the incidence of pneumonitis; 43% (23/53) of patients in the XRT arm and 9% (4/44) in the A + XRT arm experienced > or = Grade 2 pneumonitis (p < 0.001) [corrected]. Forty-nine percent (26/53) of patients in the XRT arm and 16% (7/44) in the A+XRT arm demonstrated changes representative of > or = Grade 2 lung damage (p < 0.001). At 6 months, fibrosis was present in 53% (19/36) receiving XRT vs. 28% (9/32) receiving A+XRT (p < 0.05). Incidence of esophagitis > or = Grade 2 during Week 4 was 42% (31/73) in the XRT arm vs. 4% (3/73) in the A+XRT arm (p < 0.001). Among 97 patients evaluable for response 2 months after XRT, complete or partial response was present in 76% (40/53) of patients in the XRT arm and 75% (33/44) in the A+XRT arm (p = 1.0).

CONCLUSION

Amifostine reduces the incidence of pneumonitis, lung fibrosis, and esophagitis in radiotherapy patients with lung cancer without compromising antitumor efficacy.

The effect of breathing and set-up errors on the cumulative dose to a lung tumor

BACKGROUND AND PURPOSE

To assess the impact of both set-up errors and respiration-induced tumor motion on the cumulative dose delivered to a clinical target volume (CTV) in lung, for an irradiation based on current clinically applied field sizes.

MATERIALS AND METHODS

A cork phantom, having a 50 mm spherically shaped polystyrene insertion to simulate a gross tumor volume (GTV) located centrally in a lung was irradiated with two parallel opposed beams. The planned 95% isodose surface was conformed to the planning target volume (PTV) using a multi leaf collimator. The resulting margin between the CTV and the field edge was 16 mm in beam's eye view. A dose of 70 Gy was prescribed. Dose area histograms (DAHs) of the central plane of the CTV (GTV+5 mm) were determined using radiographic film for different combinations of set-up errors and respiration-induced tumor motion. The DAHs were evaluated using the population averaged tumor control probability (TCP(pop)) and the equivalent uniform dose (EUD) model.

RESULTS

Compared with dose volume histograms of the entire CTV, DAHs overestimate the impact of tumor motion on tumor control. Due to the choice of field sizes a large part of the PTV will receive a too low dose resulting in an EUD of the central plane of the CTV of 68.9 Gy for the static case. The EUD drops to 68.2, 66.1 and 51.1 Gy for systematic set-up errors of 5, 10 and 15 mm, respectively. For random set-up errors of 5, 10 and 15 mm (1 SD), the EUD decreases to 68.7, 67.4 and 64.9 Gy, respectively. For similar amplitudes of respiration-induced motion, the EUD decreases to 68.8, 68.5 and 67.7 Gy, respectively. For a clinically relevant scenario of 7.5 mm systematic set-up error, 3 mm random set-up error and 5 mm amplitude of breathing motion, the EUD is 66.7 Gy. This corresponds with a tumor control probability TCP(pop) of 41.7%, compared with 50.0% for homogeneous irradiation of the CTV to 70 Gy.

CONCLUSION

Systematic set-up errors have a dominant effect on the cumulative dose to the CTV. The effect of breathing motion and random set-up errors is smaller. Therefore the gain of controlling breathing motion during irradiation is expected to be small and efforts should rather focus on minimizing systematic errors. For the current clinically applied field sizes and a clinically relevant combination of set-up errors and breathing motion, the EUD of the central plane of the CTV is reduced by 3.3 Gy, at maximum, relative to homogeneous irradiation of the CTV to 70 Gy, for our worst case scenario.

Skin markings in external radiotherapy by temporary tattooing with henna: improvement of accuracy and increased patient comfort

PURPOSE

To guarantee invariable skin markings in patients undergoing a course of external radiotherapy, especially using conformal techniques. Cutaneous markings with henna also increase patient comfort, because washing and showering are allowed.

METHODS AND MATERIALS

Henna, a completely natural product, is a skin colorant with a history of 5,000 years. It is applied to the skin in the form of a paste. While drying, henna stains the superficial skin layers for several weeks, and the marked area can be exposed to water arbitrarily. In case of fading of the stain before the end of radiotherapy, the marking procedure can be repeated. From November 1998 until March 2000, we performed skin markings with henna in 158 patients with different tumor sites. The majority of patients received conformal radiotherapy techniques. All patients have been evaluated concerning durability of the markings, the

RESULTS

The median durability of henna staining is 23 days (range 12-48 days). On average, two marking procedures (range 1-4) are necessary for a patient treated with curative intent. Although washing and showering are freely permitted, no adverse cutaneous side effects (e.g., erythema, allergic reactions) have been observed.

CONCLUSIONS

Skin marking by temporary tattooing with henna increases the accuracy of external radiotherapy. It yields stable and invariable markings for the entire course of radiotherapy and also increases the comfort of patients.

Dose escalation in non-small-cell lung cancer using three-dimensional conformal radiation therapy: update of a phase I trial

PURPOSE

High-dose radiation may improve outcomes in non-small-cell lung cancer (NSCLC). By using three-dimensional conformal radiation therapy and limiting the target volume, we hypothesized that the dose could be safely escalated.

MATERIALS AND METHODS

A standard phase I design was used. Five bins were created based on the volume of normal lung irradiated, and dose levels within bins were chosen based on the estimated risk of radiation pneumonitis. Starting doses ranged from 63 to 84 Gy given in 2.1-Gy fractions. Target volumes included the primary tumor and any nodes >or= 1 cm on computed tomography. Clinically uninvolved nodal regions were not included purposely. More recently, selected patients received neoadjuvant cisplatin and vinorelbine.

RESULTS

At the time of this writing, 104 patients had been enrolled. Twenty-four had stage I, four had stage II, 43 had stage IIIA, 26 had stage IIIB, and seven had locally recurrent disease. Twenty-five received chemotherapy, and 63 were assessable for escalation. All bins were escalated at least twice. Although grade 2 radiation pneumonitis occurred in five patients, grade 3 radiation pneumonitis occurred in only two. The maximum-tolerated dose was only established for the largest bin, at 65.1 Gy. Dose levels for the four remaining bins were 102.9, 102.9, 84 and 75.6 Gy. The majority of patients failed distantly, though a significant proportion also failed in the target volume. There were no isolated failures in clinically uninvolved nodal regions.

CONCLUSION

Dose escalation in NSCLC has been accomplished safely in most patients using three-dimensional conformal radiation therapy, limiting target volumes, and segregating patients by the volume of normal lung irradiated.

Optimum beam angles for the conformal treatment of lung cancer: a CT simulation study

Treatment of lung cancer is often performed with cone-down oblique beams to spare spinal cord and normal structures. However, there is no optimum technique to determine oblique beam angles when a CT simulation is not available. Impact of oblique beam angle was investigated in this study. Fifteen patients with centrally located lung tumors were immobilized and scanned using a CT simulator. The target volumes, left and right lungs, and spinal cord were delineated on each slice. Patients were simulated starting with anterior-posterior treatment beams and subsequently an oblique opposed pair beam from 0 degrees up to 60 degrees at an interval of 5 degrees to optimize the projection of target-to-cord distance and minimize the lung volume in the treatment fields. Analysis was performed with a dose volume histogram (DVH) in each beam orientation. The distance between the target volume and spinal cord was linearly related to the angle of the beam. A larger angle facilitated further sparing of the spinal cord; however, progressively more lung volume was exposed. The 50% DVH data for lung volume was used as an indicator of lung volume. Although, the minimum lung volume was irradiated with an angle of 30 degrees, the additional lung treated increased by only 8 +/- 7% of the total lung volume for 30-60 degrees beam angles and cord distance increased by 18.5 mm. A 30 degrees oblique parallel-opposed beam for the cone-down treatment of lung provided minimum lung volume in the irradiated field; however, the spinal cord distance increased linearly with beam angle. A CT simulator is ideally suited for simulation of lung cancer to maximize the clearance from the spinal cord and minimize the additional lung volume irradiated. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 359-365 (2000).

In-field and out-of-field effects in partial volume lung irradiation in rodents: possible correlation between early dna damage and functional endpoints

PURPOSE

Recent observations have shown that there are regional variations in radiation response in mouse lung as measured by functional assays. Furthermore, there are both in-field and out-of-field effects in radiation-induced lung damage as observed by DNA assay in rats. The purpose of this work is: (a) to examine mice lethality data following partial volume lung irradiation to assess the possibility of directional or regional effects, (b) to evaluate the correlation between mice lethality data and DNA damage assayed by micronuclei production in rat lung, and (c) to re-interpret mice lethality considering the existence of directional effects in lung cellular response to partial volume irradiation.

METHODS AND MATERIALS

The lethality data for mice, generated at the M. D. Anderson Cancer Center, Houston, and micronuclei yield data for rats obtained at Princess Margaret Hospital, Toronto, were used. A radiobiological model that allows for out-of-field and in-field effects for lung cell damage and lung response was developed. This model is based on the observation of DNA damage in shielded parts of rat lung that was assumed relevant to cell lethality and consequently overall lung response.

RESULTS

While the experimental data indicated directional or regional volume effects, the applicability of dose and volume as sole predictors of lung response to radiation was found to be unreliable for lower lung (base) irradiation in mice. This conforms well to rat lung response where micronuclei were observed in shielded apical parts of lung following base irradiation. The radiobiological model, which was specifically developed to account for the lung response outside of primary irradiated volume, provides a good fit to mice lethality data, using parameters inferred from rat micronuclei data.

CONCLUSION

Response to lung irradiation in rodents, in particular, elevated sensitivity to base irradiation, can be interpreted with a hypothesis of in-field and out-of-field effects for cellular response. If the existence of these effects for lung is subsequently proven in humans, it will require the incorporation of geometrical and directional information in normal tissue complication probability calculations for lung. These considerations are ignored in present approaches based only on conventional dose-volume histograms.

Evaluation of microscopic tumor extension in non-small-cell lung cancer for three-dimensional conformal radiotherapy planning

PURPOSE

One of the most difficult steps of the three-dimensional conformal radiotherapy (3DCRT) is to define the clinical target volume (CTV) according to the degree of local microscopic extension (ME). In this study, we tried to quantify this ME in non-small-cell lung cancer (NSCLC).

MATERIAL AND METHODS

Seventy NSCLC surgical resection specimens for which the border between tumor and adjacent lung parenchyma were examined on routine sections. This border was identified with the naked eye, outlined with a marker pen, and the value of the local ME outside of this border was measured with an eyepiece micrometer. The pattern of histologic spread was also determined.

RESULTS

A total of 354 slides were examined, corresponding to 176 slides for adenocarcinoma (ADC) and 178 slides for squamous cell carcinoma (SCC). The mean value of ME was 2.69 mm for ADC and 1.48 mm for SCC (p = 0.01). The usual 5-mm margin covers 80% of the ME for ADC and 91% for SCC. To take into account 95% of the ME, a margin of 8 mm and 6 mm must be chosen for ADC and SCC, respectively. Aerogenous dissemination was the most frequent pattern observed for all groups, followed by lymphatic invasion for ADC and interstitial extension for SCC.

CONCLUSION

The ME was different between ADC and SCC. The usual CTV margin of 5 mm appears inadequate to cover the ME for either group, and it must be increased to 8 mm and 6 mm for ADC and SCC, respectively, to cover 95% of the ME. This approach is obviously integrated into the overall 3DCRT procedure and with other margins.

The physical parameters and molecular events associated with radiation-induced lung toxicity

Radiation therapy (RT) is frequently used to treat patients with tumors in and around the thorax. Clinical radiation pneumonitis is a common side effect, occurring in 5% to 20% of patients. Efforts to identify patients at risk for pneumonitis have focused on physical factors, such as dose and volume. Recently, the underlying molecular biological mechanisms behind RT-induced lung injury have come under study. Improved knowledge of the molecular events associated with RT-induced lung injury may translate into a better ability to individualized therapy. This review discusses our current understanding of the physical and molecular factors contributing to RT-induced pulmonary injury.

Point: the potential importance of elective nodal irradiation in the treatment of non-small cell lung cancer

Patients who receive radiation therapy for non-small cell lung cancer (NSCLC) will require accurate targeting of the grossly involved primary and nodal disease. However, the treatment of grossly uninvolved elective nodal sites that may harbor microscopic occult disease is controversial. In simple terms, physicians are guided by 1 of 2 paradigms when they decide about the use of elective nodal irradiation in NSCLC. First, one may consider that high doses of radiation therapy for the primary and grossly involved lymph nodes represents the most important aspect of treatment and that elective irradiation of potential occult micrometastasis is not necessary because it may limit the doses that can be given to the gross disease. Additionally, this line of thought often includes the belief that most or all patients with occult micrometastasis are not curable. Alternatively, one may consider that the evidence for a dose response, for grossly involved NSCLC, beyond 60 Gy is very limited and that the omission of elective nodal irradiation obviates the chance for cure in many patients. These small deposits of tumor in regional nodes are common, are amenable to low doses of radiation (50 Gy), and treatment of these lesions does result in cures. This review focuses on this latter paradigm and the available evidence to support it.

Results of multifield conformal radiation therapy of nonsmall-cell lung carcinoma using multileaf collimation beams

A five-field conformal technique with three-dimensional radiation therapy treatment planning (3-DRTP) has been shown to permit better definition of the target volume for lung cancer, while minimizing the normal tissue volume receiving greater than 50% of the target dose. In an initial study to confirm the safety of conventional doses, we used the five-field conformal 3-DRTP technique. We then used the technique in a second study, enhancing the therapeutic index in a series of 42 patients, as well as to evaluate feasibility, survival outcome, and treatment toxicity. Forty-two consecutive patients with nonsmall-cell lung carcinoma (NSCLC) were evaluated during the years 1993-1997. The median age was 60 years (range 34-80). The median radiation therapy (RT) dose to the gross tumor volume was 6,300 cGy (range 5,000-6,840 cGy) delivered over 6 to 6.5 weeks in 180-275 cGy daily fractions, 5 days per week. There were three patients who received a split course treatment of 5,500 cGy in 20 fractions, delivering 275 cGy daily with a 2-week break built into the treatment course after 10 fractions. The stages of disease were II in 2%, IIIA in 40%, IIIB in 42.9%, and recurrent disease in 14.3% of the patients. The mean tumor volume was 324.14 cc (range 88.3-773.7 cc); 57.1% of the patients received combined chemoradiotherapy, while the others were treated with radiation therapy alone. Of the 42 patients, 7 were excluded from the final analysis because of diagnosis of distant metastasis during treatment. Two of the patients had their histology reinterpreted as being other than NSCLC, 2 patients did not complete RT at the time of analysis, and 1 patient voluntarily discontinued treatment because of progressive deterioration. Median follow-up was 11.2 months (range 3-32.5 months). Survival for patients with Stage III disease was 70.2% at 1 year and 51.5% at 2 years, with median survival not yet reached. Local control for the entire series was 23.3+/-11.4% at 2 years. However, for Stage III patients, local control was 50% at 1 year and 30% at 2 years. Patients who received concurrent chemotherapy had significantly improved survival (P = 0.002) and local control (P = 0.004), compared with RT alone. Late esophageal toxicity of > or =Grade 3 occurred in 14.1+/-9.3% of patients (3 of 20) receiving combined chemoradiotherapy, but in none of the 15 patients treated with RT alone. Pulmonary toxicity limited to Grades 1-2 occurred in 6.8% of the patients, and none developed > or =Grade 3 pulmonary toxicity. Patients with locally advanced NSCLC, who commonly have tumor volumes in excess of 200 cc, presenta challenge for adequate dose delivery without significant toxicity. Our five-field conformal 3-DRTP technique, which incorporates treatment planning by dose/volume histogram (DVH) was associated with minimal toxicity and may facilitate dose escalation to the gross tumor.

The rationale and use of three-dimensional radiation treatment planning for lung cancer

Treatment of lung cancer with conventional radiation therapy is associated with suboptimal local tumor control and poor long-term survival. Poor local tumor control may result from inaccurate tumor targeting, failure to satisfactorily conform to dose distribution with the target volume, and/or inadequate radiation doses. Three-dimensional treatment planning is a radiotherapy technique that provides more accurate dose targeting via the direct transfer of three-dimensional anatomic information from diagnostic scans into the planning process. This technology can assist treatment planning by providing dose-volume histograms, an estimation of normal tissue complication probabilities, and facilitate dose escalation. Preliminary clinical studies suggest that this is a feasible approach worthy of additional study. The three-dimensional tools provide new opportunities to better understand radiation-induced changes in pulmonary function.

Evaluation of a target contouring protocol for 3D conformal radiotherapy in non-small cell lung cancer

BACKGROUND

A protocol for the contouring of target volumes in lung cancer was implemented. Subsequently, a study was performed in order to determine the intra and inter-clinician variations in contoured volumes.

MATERIALS AND METHODS

Six radiation oncologists (RO) contoured the gross tumour volume (GTV) and/or clinical target volume (CTV), and planning target volume (PTV) for three patients with non-small cell lung cancer (NSCLC), on two separate occasions. These were, respectively, a well-circumscribed T1N0M0 lesion, an irregularly shaped T2N0M0 lesion, and a T2N2M0 tumour. Detailed diagnostic radiology reports were provided and contours were entered into a 3D planning system. The target volumes were calculated and beams-eye view (BEV) plots were generated to visualise differences in contouring. A software tool was used to expand the GTV and CTV in three dimensions for an automatically derived PTV.

RESULTS

Significant inter-RO variations in contoured target volumes were observed for all patients, and these were greater than intra-RO differences. The ratio of the largest to smallest contoured volume ranged from 1.6 for the GTV in the T1N0 lesion, to 2.0 for the PTV in the T2N2 lesion. The BEV plots revealed significant inter-RO variations in contouring the mediastinal CTV. The PTV's derived using a 3D margin programme were larger than manually contoured PTV's. These variations did not correlate with the experience of ROs.

CONCLUSIONS

Despite the use of an institutional contouring protocol, significant interclinician variations persist in contouring target volumes in NSCLC. Additional measures to decrease such variations should be incorporated into clinical trials.

[Conformal radiotherapy of non-small-cell lung cancer]

About one third of lung cancers initially present with a localised disease, without any curative surgery potential, because of local spread or comorbidity. Definitive radiation, alone or combined with chemotherapy, then represents the treatment of choice for these patients. The results, however, are disappointing, with a biopsy-proven local control of 10% at two years and a 5-10% five-year survival rate. These poor results may be partially explained by the difficulties in delineating the tumour volume as well as the dose limitations due to poor tolerance of surrounding normal organs. Lung parenchyma sequelae remain daily worrying events for the oncologist. The advent of 3D conformal radiation therapy (3DRT) allows progress and innovations, including the use of modern imaging techniques, sophisticated dosimetry and treatment planning, efficient immobilisation devices and on-line verification procedures. With more precise (and time-consuming) procedures, 3DRT will allow a better tumour volume delineation, an increased tumour dose and a dose limitation in normal tissues. These improvements may help increase local control and survival results. 3DRT, which has been used for several years for prostate cancer and benefits from recent imaging improvements, will now allow treatment of other locations, such as lung cancer, with conformal therapy. The few preliminary results are encouraging. This work reviews the current data and remaining questions regarding lung cancer treated with 3DRT, and presents and discusses the literature before discussing future trends in this area.

Radiotherapy for lung cancer: target splitting by asymmetric collimation enables reduction of radiation doses to normal tissues and dose escalation

PURPOSE

This study was performed to develop a method of reducing the radiation doses to normal thoracic tissues, increasing the target dose, especially in the primary radiotherapy of non-small cell lung cancer (NSCLC), and to evaluate acute/subacute toxicity of dose escalation.

METHODS AND MATERIALS

From December 1195 to March 1998, the technique of target splitting has been applied to 58 patients. In this period, 30 patients were treated with doses > 80 Gy (ICRU-specification, mean 85.1 Gy, range 80. 1-90.2 Gy). The target volume is split into a cranial part (e.g., upper mediastinum) and a caudal part (e.g., primary tumor and middle mediastinum). Both volumes are planned and treated independently, using conformal irradiation techniques for both parts with half-collimated fields to prevent over- or underdosage in the junction plane. After fine-adjustment of the jaws, a verification film, exposed in a polymethylmethacrylate (PMMA) phantom, demonstrates the homogeneity of dose in the entire target volume. For comparison with conventional techniques, planning to identical doses is performed for 5 patients. Dose-volume histograms (DHVs) for normal lung tissue are presented for both methods.

RESULTS

The irradiated volume of normal tissue of the ipsilateral lung can be lowered at dose levels > or = 65, > or =45 Gy, and > or = 20 Gy to values of 37% (range 25-54%), 49% (range 46-54%), and 86% (range 55-117%), respectively. Other organs at risk, such as heart or esophagus, can also be spared significantly. Only 1 patient showed a transient grade 3 toxicity (pneumonitis), and there where no grade 4 acute/subacute side-effects. Two patients with Stage III A central tumors in close proximity to the large vessels died due to a pulmonary hemorrhage 2 and 4 months after therapy, respectively. No patient developed esophagitis. Antimycotic prophylaxis for esophagitis and posttherapeutic steroid prophylaxis for pneumonitis for several weeks were routinely used.

CONCLUSION

The technique of target splitting by asymmetric collimation helps to increase conformation, and thus enhances the sparing of normal tissues. It can be used whenever there is a marked difference in the shape of the planning target volume (PTV) in a cranio-caudal direction. This technique can principally be handled with 2D-planning systems, because it is coplanar. We consider target splitting as an important tool for dose escalation in the primary radiotherapy of NSCLC, that should also be used for other lung cancer patients necessitating moderate doses only.

Beam intensity modulation to reduce the field sizes for conformal irradiation of lung tumors: a dosimetric study

PURPOSE

In conformal radiotherapy of lung tumors, penumbra broadening in lung tissue necessitates the use of larger field sizes to achieve the same target coverage as in a homogeneous environment. In an idealized model configuration, some fundamental aspects of field size reduction were investigated, both for the static situation and for a moving tumor, while maintaining the dose homogeneity in the target volume by employing a simple beam-intensity modulation technique.

METHODS AND MATERIALS

An inhomogeneous phantom, consisting of polystyrene, cork, and polystyrene layers, with a 6 x 6 x 6 cm3 polystyrene cube inside the cork representing the tumor, was used to simulate a lung cancer treatment. Film dosimetry experiments were performed for an AP-PA irradiation technique with 8-MV or 18-MV beams. Dose distributions were compared for large square fields, small square fields, and intensity-modulated fields in which additional segments increase the dose at the edge of the field. The effect of target motion was studied by measuring the dose distribution for the solid cube, displaced with respect to the beams.

RESULTS

For the 18-MV beam, the field sizes required to establish a sufficient target coverage are larger than for the 8-MV beam. For each beam energy, the mean dose in cork can significantly be reduced (at least a factor of 1.6) by decreasing the field size with 2 cm, while keeping the mean target dose constant. Target dose inhomogeneity for these smaller fields is limited if the additional edge segments are applied for 8% of the number of monitor units given with the open fields. The target dose distribution averaged over a motion cycle is hardly affected if the target edge does not approach the field edge to within 3 mm.

CONCLUSIONS

For lung cancer treatment, a beam energy of 8 MV is more suitable than 18 MV. The mean lung dose can be significantly reduced by decreasing the field sizes of conformal fields. The smaller fields result in the same biological effect to the tumor if the mean target dose is kept constant. Intensity modulation can be employed to maintain the same target dose homogeneity for these smaller fields. As long as the target (with a 3 mm margin) stays within the field portal, application of a margin for target motion is not necessary.

Study of lung density corrections in a clinical trial (RTOG 88-08). Radiation Therapy Oncology Group

PURPOSE

To investigate the effect of lung density corrections on the dose delivered to lung cancer radiotherapy patients in a multi-institutional clinical trial, and to determine whether commonly available density-correction algorithms are sufficient to improve the accuracy and precision of dose calculation in the clinical trials setting.

METHODS AND MATERIALS

A benchmark problem was designed (and a corresponding phantom fabricated) to test density-correction algorithms under standard conditions for photon beams ranging from 60Co to 24 MV. Point doses and isodose distributions submitted for a Phase III trial in regionally advanced, unresectable non-small-cell lung cancer (Radiation Therapy Oncology Group 88-08) were calculated with and without density correction. Tumor doses were analyzed for 322 patients and 1236 separate fields.

RESULTS

For the benchmark problem studied here, the overall correction factor for a four-field treatment varied significantly with energy, ranging from 1.14 (60Co) to 1.05 (24 MV) for measured doses, or 1.17 (60Co) to 1.05 (24 MV) for doses calculated by conventional density-correction algorithms. For the patient data, overall correction factors (calculated) ranged from 0.95 to 1.28, with a mean of 1.05 and distributional standard deviation of 0.05. The largest corrections were for lateral fields, with a mean correction factor of 1.11 and standard deviation of 0.08.

CONCLUSIONS

Lung inhomogeneities can lead to significant variations in delivered dose between patients treated in a clinical trial. Existing density-correction algorithms are accurate enough to significantly reduce these variations.

Conformal radiotherapy of Stage III non-small cell lung cancer: a class solution involving non-coplanar intensity-modulated beams

PURPOSE

We developed a semiautomatic class solution to irradiate centrally located Stage III non-small cell lung cancer (NSCLC), involving a beam intensity modulation technique and optimization using a biophysical cost function.

METHODS AND MATERIALS

Treatment for 10 patients with Stage III NSCLC was planned, using a conventional three- or four-beam three-dimensional (3D) technique and two techniques involving, respectively, seven (BIM1) and five (BIM2) noncoplanar beam incidences with intensity modulation. Two planning target volumes were defined: PTV1 included macroscopic tumor volume and PTV2 included macroscopic and microscopic disease. Beams were divided into beam parts (segments) and their outlines were defined during virtual simulation. Optimization using a biophysical cost function determined beam weights, segment weights, and wedge angles. Biological end points included tumor control probability of both target volumes (TCP1 and TCP2) and normal tissue complication probability (NTCP) of heart, lung, and spinal cord. The resulting uncomplicated local control probability (UCLP) was calculated. Physical end points included dose at PTV1 expressed as a dose minimum and dose maximum. Target-dose inhomogeneity was constrained in all plans.

RESULTS

Concerning tumor evaluation, TCP1 was 74% (range 54-89%) for the 3D plan, 78.0% (range 62-94%) for BIM1, and 86.0% (range 59-93%) for BIM2. TCP1*TCP2 was, respectively, 67.0% (range 39-81%), 73.0% (range 56-94%), and 81.0% (range 54-93%). Minimum doses to PTV1 were 85, 80, and 88 Gy with the three respective techniques, while dose maxima were 89, 101, and 100 Gy. NTCPs of lung were 45.0% (range 11-75%) for 3D, 19.5% (range 8-59%) for BIM1, and 24.5% (range 3-61%) for BIM2. NTCPs of heart and spinal cord were comparable for all techniques. ULCPs were 37.0% (range 9-73%), 52.5% (range 22-86%), and 60.0% (range 20-85%), respectively. Applying physical limits to ensure clinical safety, minimum doses at PTV1 were recalculated. These were 72, 71, and 74 Gy for 3D, BIM1, and BIM2, respectively.

CONCLUSION

The BIM2 plan is a candidate class solution for dose escalation studies in centrally located Stage III NSCLC.