Intensity-modulated radiotherapy for locally advanced non-small-cell lung cancer: a dose-escalation planning study

Single isocenter versus dual isocenter treatment using flattening filter-free and jaw-tracking volumetrically modulated arc therapy for boot-shaped lung cancer: Evaluation of dosimetric and feasibility

BACKGROUND

To determine whether a dual-isocenter volumetrically modulated arc therapy (VMAT) technique results in lower normal pulmonary dosage compared to a traditional single isocenter technique for boot-shaped lung cancer.

METHODS

A cohort of 15 patients with advanced peripheral or central lung cancer who had metastases in the mediastinum and supraclavicular lymph nodes was randomly selected for this retrospective study. VMAT plans were generated for each patient using two different beam alignment techniques with the 6-MV flattening filter-free (FFF) photon beam: single-isocenter jaw-tracking VMAT based on the Varian TrueBeam linear accelerator (S-TV), and dual-isocenter VMAT based on both TrueBeam (D-TV) and Halcyon linear accelerator (D-HV). For all 45 treatment plans, planning target volume (PTV) dose coverage, conformity/homogeneity index (CI/HI), mean heart dose (MHD), mean lung dose (MLD) and the total lung tissue receiving 5, 20, 30 Gy (V5, V20, V30) were evaluated. The monitor units (MUs), delivery time, and plan quality assurance (QA) results were recorded.

RESULTS

The quality of the objectives of the three plans was comparable to each other. In comparison with S-TV, D-TV and D-HV improved the CI and HI of the PTV (p < 0.05). The MLD was 13.84 ± 1.44 Gy (mean ± SD) for D-TV, 14.22 ± 1.30 Gy and 14.16 ± 1.42 Gy for S-TV and D-HV, respectively. Lungs-V5Gy was 50.78 ± 6.24%, 52.00 ± 7.32% and 53.36 ± 8.48%, Lungs-V20Gy was 23.72 ± 2.27%, 26.18 ± 2.86% and 24.96 ± 3.09%, Lungs-V30Gy was 15.69 ± 1.76%, 17.20 ± 1.72% and 16.52 ± 2.07%. Compared to S-TV, D-TV provided statistically significant better protection for the total lung, with the exception of the lungs-V5. All plans passed QA according the gamma criteria of 3%/3 mm.

CONCLUSIONS

Taking into account the dosimetric results and published clinical data on radiation-induced pulmonary injury, dual-isocenter jaw-tracking VMAT may be the optimal choice for treating boot-shaped lung cancer.

IMRT in the treatment of locally advanced or inoperable NSCLC in the pre-durvalumab era: clinical outcomes and pattern of relapses, experience from the Oscar Lambret Center

Background

Intensity-modulated conformal radiotherapy (IMRT) has become the technique of choice for the treatment of locally advanced or inoperable non-small cell lung cancer (NSCLC). Nevertheless, this technique presents dosimetric uncertainties, particularly in treating moving targets such as pulmonary neoplasms. Moreover, it theoretically increases the risk of isolated nodal failure (INF) due to reduced incidental irradiation.

Objective

The objective of this study was to evaluate the efficacy and safety of IMRT in patients with inoperable NSCLC and to describe the pattern of relapses.

Methods

Patients with locally advanced NSCLC treated with radiotherapy and chemotherapy between 2015 and 2018 at the Oscar Lambret Center were retrospectively included in the study. Overall and progression-free survival were estimated using the Kaplan-Meier method. The cumulative incidence of the different components of relapse was estimated using the Kalbfleisch and Prentice method. Prognostic factors for relapse/death were investigated using the Cox model. A comparison with literature data was performed using a one-sample log-rank test.

Results

Seventy patients were included, and 65 patients (93%) had stage III disease. All the patients received chemotherapy, most frequently with cisplatin and navelbine. The dose received was 66 Gy administered in 33 fractions. The median follow-up and survival were 49.1 and 39.1 months, respectively. A total of 35 deaths and 43 relapses, including 29 with metastatic components, were reported. The overall survival rates at 1 and 2 years were 80.2% (95% confidence interval 68.3%-88.0%) and 67.2% (95% confidence interval 54.2%-77.3%), respectively. Locoregional relapse was observed in 14 patients, including two INF, one of which was located in the lymph node area adjacent to the clinical target volume. Median relapse-free survival was 15.2 months. No variable was statistically associated with the risk of relapse/death in multivariate analysis. Seven patients (10%) experienced grade 3 or higher toxicity.

Conclusion

The use of IMRT for locally advanced or inoperable NSCLC led to favorable long-term clinical outcomes. The rate of locoregional relapse, particularly isolated lymph node failure, was low and comparable with that of the three-dimensional radiotherapy series, as was the rate of early and late toxicities.

Isotoxic investigation of 18F-FDG PET/CT-guided dose escalation with intensity-modulated radiotherapy for LA-NSCLC

PURPOSE

This research compared differences of dosimetric and biological parameters between PET/CT-guided isotoxic SIB-IMRT plans and conventional radiotherapy plans for patients with LA-NSCLC, and it also evaluated the factors that affect dose escalation.

MATERIALS AND METHODS

This study consisted of a retrospective cohort of thirty patients with IIIA-IIIB NSCLC. SIB-IMRT (Plan_iso) and conventional radiotherapy (Plan_primary) plans were generated using auto-planning. Dosimetric parameters such as mean lung dose (MLD) and other indicators were compared. Tumor control probability (TCP) of PTV and normal tissue complication probability (NTCP) of total lung, heart, esophagus, and spinal cord were calculated. The relationships between dose escalation and 3 D length of PTV and other factors were analyzed. Paired-samples t-test, Mann-Whitney U test, and Chi-Square test were performed for comparisons between datasets. A P < .05 was considered statistically significant.

RESULTS

The dosimetric parameters of PTV in Plan_iso were higher than those of PTV in Plan_primary, and there were significant differences (p < .05). Compared with Plan_primary, Plan_iso slightly increased dosimetric parameters of the total lung, heart, spinal cord, esophagus, and MUs. The absolute differences were small. TCPs of PTV in Plan_iso were significantly higher than those in Plan_primary. NTCPs of the total lung, esophagus, and spinal cord in Plan_iso were higher than those in Plan_primary. There were significant differences, but the absolute differences were small. NTCP of heart in Plan_iso was slightly higher than that in Plan_primary, but there was no statistical difference.

CONCLUSIONS

For LA-NSCLC, the SIB based on isotoxic radiotherapy can significantly increase TCP under the premise that the toxicity of OARs is comparable.

GOECP/SEOR clinical recommendations for lung cancer radiotherapy during the COVID-19 pandemic

The coronavirus disease 2019 crisis has had a major and highly complex impact on the clinical practice of radiation oncology worldwide. Spain is one of the countries hardest hit by the virus, with devastating consequences. There is an urgent need to share experiences and offer guidance on decision-making with regard to the indications and standards for radiation therapy in the treatment of lung cancer. In the present article, the Oncological Group for the Study of Lung Cancer of the Spanish Society of Radiation Oncology reviews the literature and establishes a series of consensus-based recommendations for the treatment of patients with lung cancer in different clinical scenarios during the present pandemic.

Individualized accelerated isotoxic concurrent chemo-radiotherapy for stage III non-small cell lung cancer: 5-Year results of a prospective study

BACKGROUND

Stage III non-small cell lung cancer (NSCLC) still has a poor prognosis. Prior studies with individualized, accelerated, isotoxic dose escalation (INDAR) with 3D-CRT showed promising results, especially in patients not treated with concurrent chemo-radiotherapy. We investigated if INDAR delivered with IMRT would improve the overall survival (OS) of stage III NSCLC patients treated with concurrent chemotherapy and radiotherapy.

PATIENTS AND METHODS

Patients eligible for concurrent chemo-radiotherapy were entered in this prospective study. Radiotherapy was given to a dose of 45 Gy/30 fractions BID (1.5 Gy/fraction), followed by QD fractions of 2 Gy until a total dose determined by the normal tissue constraints. The primary endpoint was OS, secondary endpoints were loco-regional relapses and toxicity.

RESULTS

From May 4, 2009 until April 26, 2012, 185 patients were included. The mean tumor dose was 66.0 ± 12.8 Gy (36-73 Gy), delivered in a mean of 39.7 fractions in an overall treatment time of 38.2 days. The mean lung dose (MLD) was 17.3 Gy. The median OS was 19.8 months (95% CI 17.3-22.3) with a 5-year OS of 24.3%. Loco-regional failures as first site of recurrence occurred in 59/185 patients (31.8%). Isolated nodal failures (INF) were observed in 3/185 patients (1.6%). Dyspnea grade 3 was seen in 3.2% of patients and transient dysphagia grade 3 in 22%.

CONCLUSIONS

INDAR with IMRT concurrently with chemotherapy did not lead to a sign of an improved OS in unselected stage III NSCLC patients.

Multi-institutional evaluation using the end-to-end test for implementation of dynamic techniques of radiation therapy in Thailand

AIM

In this study, an accuracy survey of intensity-modulated radiation therapy (IMRT) and volumetric arc radiation therapy (VMAT) implementation in radiotherapy centers in Thailand was conducted.

BACKGROUND

It is well recognized that there is a need for radiotherapy centers to evaluate the accuracy levels of their current practices, and use the related information to identify opportunities for future development.

MATERIALS AND METHODS

An end-to-end test using a CIRS thorax phantom was carried out at 8 participating centers. Based on each center's protocol for simulation and planning, linac-based IMRT or VMAT plans were generated following the IAEA (CRP E24017) guidelines. Point doses in the region of PTVs and OARs were obtained from 5 ionization chamber readings and the dose distribution from the radiochromic films. The global gamma indices of the measurement doses and the treatment planning system calculation doses were compared.

RESULTS

The large majority of the RT centers (6/8) fulfilled the dosimetric goals, with the measured and calculated doses at the specification points agreeing within ±3% for PTV and ±5% for OARS. At 2 centers, TPS underestimated the lung doses by about 6% and spinal cord doses by 8%. The mean percentage gamma pass rates for the 8 centers were 98.29 ± 0.67% (for the 3%/3 mm criterion) and 96.72 ± 0.84% (for the 2%/2 mm criterion).

CONCLUSIONS

The 8 participating RT centers achieved a satisfactory quality level of IMRT/VMAT clinical implementation.

The potential for increased tumor control probability in non-small cell lung cancer with a hypofractionated integrated boost to the gross tumor volume

Treatment outcomes in locally advanced non-small cell lung cancer (NSCLC) to date have been poor, with normal tissue toxicity often limiting the dose that can be delivered to the tumor. Treatment intensification in NSCLC via targeted dose escalation with modern delivery techniques may offer the potential for a significant increase in tumor control probability (TCP) without a clinically significant increase in organ-at-risk (OAR) toxicity. In this planning study, 20 patients were re-planned with a volumetric modulated arc therapy (VMAT) and an inhomogeneous dose distribution with iteratively escalated doses to the gross tumor volume (iGTV) (composite GTV across multiple 4-dimensional computed tomography [4DCT] phases) in a series of 20 fraction regimes. For each plan OAR doses, target coverage and predicted TCPs were collected and compared with homogenous 3-dimensional (3D) and VMAT plans, as well as with each other. In 70% of patients, it was possible to escalate to 75 Gy in 20 fractions within OAR tolerances, opening the possibility of treating these patients to a biological effective dose (BED) of 103.1 Gy₁₀. This planning study forms the basis of a clinical trial INTENSE (Inhomogeneous Targeted Dose Escalation in Non-Small CEll Lung Cancer), CTRIAL 15-47.

Radiation therapy-induced metastasis: radiobiology and clinical implications

Radiation therapy is an effective means of achieving local control in a wide range of primary tumours, with the reduction in the size of the tumour(s) thought to mediate the observed reductions in metastatic spread in clinical trials. However, there is evidence to suggest that the complex changes induced by radiation in the tumour environment can also present metastatic risks that may counteract the long-term efficacy of the treatment. More than 25 years ago, several largely theoretical mechanisms by which radiation exposure might increase metastatic risk were postulated. These include the direct release of tumour cells into the circulation, systemic effects of tumour and normal tissue irradiation and radiation-induced changes in tumour cell phenotype. Here, we review the data that has since emerged to either support or refute these putative mechanisms focusing on how the unique radiobiology underlying modern radiotherapy modalities might alter these risks.

Normal lung sparing Tomotherapy technique in stage III lung cancer

PURPOSE

Radiation pneumonitis (RP) has been a challenging obstacle in treating stage III lung cancer patients. Beam angle optimization (BAO) technique for Tomotherapy was developed to reduce the normal lung dose for stage III non-small cell lung cancer (NSCLC). Comparative analyses on plan quality by 3 different Intensity-modulated radiation therapy (IMRT) methods with BAO were done.

MATERIALS AND METHODS

Ten consecutive stage IIIB NSCLC patients receiving linac-based static IMRT (L-IMRT) with total 66 Gy in 33 fractions to the PTV were selected. Two additional Tomotherapy-based IMRT plans (helical beam (TH-IMRT) and static beam (TD-IMRT)) were generated on each patient. To reduce the normal lung dose, Beam angles were optimized by using complete and directional block functions in Tomotherapy based on knowledge based statistical analysis. Plan quality was compared with target coverage, normal organ sparing capability, and normal tissue complication probability (NTCP). Actual beam delivery times and risk of RP related with planning target volume (PTV) were also evaluated.

RESULTS

The best PTV coverage measured by conformity index and homogeneity index was achievable by TH-IMRT (0.82 and 1.06), followed by TD-IMRT (0.81 and 1.07) and L-IMRT (0.75 and 1.08). Mean lung dose was the lowest in TH-IMRT plan followed by TD-IMRT and L-IMRT, all of which were ≤20 Gy. TH-IMRT plan could significantly lower the lung volumes receiving low to medium dose levels: V5~30 when compared to L-IMRT plan; and V5~20 when compared to TD-IMRT plan, respectively. TD-IMRT plan was significantly better than L-IMRT with respects to V20 and V30 and there was no significant difference with respect to V40 among three plans. The NTCP of the lung was the lowest in TH-IMRT plan, followed by TD-IMRT and L-IMRT (6.42% vs. 6.53% vs. 8.11%). Beam delivery time was the shortest in TD-IMRT plan followed by L-IMRT. As PTV length increased, NTCP and Mean lung dose proportionally increased significantly in all three plans.

CONCLUSION

Advantageous profiles by TH-IMRT could be achieved by BAO by complete and directional block functions. Current observation could help radiation oncologists to make wise selection of IMRT method for stage IIIB NSCLC.

The relationship between dosimetric factors, side effects, and survival in patients with non-small cell lung cancer treated with definitive radiotherapy

The patients with non-small cell lung cancer (NSCLC) treated with definitive conformal radiotherapy (RT) were evaluated in terms of side effects and survival. Normal tissue complication probability (NTCP) was calculated for 68 patients treated between 2009 and 2012. Clinical and dosimetric factors were analyzed. The median dose of 63 Gy (range: 54 to 70 Gy) was given with conformal RT with blocks (n = 37), 3-dimensional conformal RT (3DCRT) (n = 11), or intensity-modulated RT (IMRT) (n = 20). Acute grade 1 to 2 radiation pneumonitis (RP) was seen in 13% of the patients. No significant relationship was found between RP and treatment and dosimetric factors (p > 0.05). There was a positive correlation between median "mean lung dose" (MLD) (17 Gy), lung V30 (20.5%), and NTCP (14%) (p < 0.001). Median and 2-year overall survival (OS) and progression-free survival (PFS) were 27 and 18 months and 51% and 42%, respectively. In univariate analysis, significant dose range for survival was found between 59.4 and 63 Gy (p < 0.01). In multivariate analysis, response (p = 0.001), fraction dose of 1.8 Gy (p = 0.002), MLD <18 Gy (p = 0.04) for OS and response (p < 0.001), total dose > 59.4 Gy (p = 0.01), and tumor biologically effective dose (BED)3_(Gy) ≤ 100.8 (p = 0.01) for PFS were found to be favorable factors. In our study, we found a linear correlation between NTCP and MLD for RP risk estimation in patients with NSCLC. Therapeutic dose range where MLD can be kept under 20 Gy with significant survival benefit was found between 59.4 and 63 Gy. Increased therapeutic efficacy will be possible using risk-adaptive RT techniques.

A Dirichlet process mixture model for automatic (18)F-FDG PET image segmentation: Validation study on phantoms and on lung and esophageal lesions

PURPOSE

The aim of this study was to implement a Dirichlet process mixture (DPM) model for automatic tumor edge identification on (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG PET) images by optimizing the parameters on which the algorithm depends, to validate it experimentally, and to test its robustness.

METHODS

The DPM model belongs to the class of the Bayesian nonparametric models and uses the Dirichlet process prior for flexible nonparametric mixture modeling, without any preliminary choice of the number of mixture components. The DPM algorithm implemented in the statistical software package R was used in this work. The contouring accuracy was evaluated on several image data sets: on an IEC phantom (spherical inserts with diameter in the range 10-37 mm) acquired by a Philips Gemini Big Bore PET-CT scanner, using 9 different target-to-background ratios (TBRs) from 2.5 to 70; on a digital phantom simulating spherical/uniform lesions and tumors, irregular in shape and activity; and on 20 clinical cases (10 lung and 10 esophageal cancer patients). The influence of the DPM parameters on contour generation was studied in two steps. In the first one, only the IEC spheres having diameters of 22 and 37 mm and a sphere of the digital phantom (41.6 mm diameter) were studied by varying the main parameters until the diameter of the spheres was obtained within 0.2% of the true value. In the second step, the results obtained for this training set were applied to the entire data set to determine DPM based volumes of all available lesions. These volumes were compared to those obtained by applying already known algorithms (Gaussian mixture model and gradient-based) and to true values, when available.

RESULTS

Only one parameter was found able to significantly influence segmentation accuracy (ANOVA test). This parameter was linearly connected to the uptake variance of the tested region of interest (ROI). In the first step of the study, a calibration curve was determined to automatically generate the optimal parameter from the variance of the ROI. This "calibration curve" was then applied to contour the whole data set. The accuracy (mean discrepancy between DPM model-based contours and reference contours) of volume estimation was below (1 ± 7)% on the whole data set (1 SD). The overlap between true and automatically segmented contours, measured by the Dice similarity coefficient, was 0.93 with a SD of 0.03.

CONCLUSIONS

The proposed DPM model was able to accurately reproduce known volumes of FDG concentration, with high overlap between segmented and true volumes. For all the analyzed inserts of the IEC phantom, the algorithm proved to be robust to variations in radius and in TBR. The main advantage of this algorithm was that no setting of DPM parameters was required in advance, since the proper setting of the only parameter that could significantly influence the segmentation results was automatically related to the uptake variance of the chosen ROI. Furthermore, the algorithm did not need any preliminary choice of the optimum number of classes to describe the ROIs within PET images and no assumption about the shape of the lesion and the uptake heterogeneity of the tracer was required.

Selective mediastinal node irradiation in non-small cell lung cancer in the IMRT/VMAT era: How to use E(B)US-NA information in addition to PET-CT for delineation?

BACKGROUND

FDG-PET-CT-based selective lymph node (LN) irradiation is standard using 3D-conformal techniques for locally advanced NSCLC. With newer techniques (intensity-modulated/volumetric-arc therapy (IMRT/VMAT)), the dose to non-involved adjacent LN decreases, which raises the question whether FDG-PET-CT-delineation is still safe. We therefore evaluated the impact of adding linear endosonography with needle aspiration (E(B)US-NA) to FDG-PET-CT in selective nodal irradiation.

METHODS

Based on literature data on sensitivity and specificity of E(B)US-NA in FDG-PET-CT-staged NSCLC, false negative (FN) rates for different constellations of CT, PET and E(B)US-NA were calculated. The algorithm was tested on consecutive patients with N2/N3 disease referred for radiotherapy in Leuven and Maastricht.

RESULTS

An algorithm determining when to include LN in the GTV is proposed, based on data from 5 meta-analyses. Adding E(B)US-NA to FDG-PET-CT decreases the FN-rate, but for PET-positive and E(B)US-negative LN, FN rates are still 14-16%. In Leuven 520 LN were analyzed, in Maastricht 364 LN; with E(B)US-NA a geographical miss was avoided in 2 (2/40=5%) and 1 (1/28=4%) patients, respectively.

CONCLUSIONS

E(B)US-NA in addition to FDG-PET-CT for mediastinal staging decreases the risk of a geographical miss with 4-5%. The impact of this small decrease on survival is unknown. The proposed algorithm may guide the radiation oncologist when to include LN in the nodal GTV.

Is IMRT Superior or Inferior to 3DCRT in Radiotherapy for NSCLC? A Meta-Analysis

Introduction

There are no adequate data to determine whether intensity-modulated radiotherapy (IMRT) is superior to three-dimensional conformal radiotherapy (3DCRT) in the treatment of non-small cell lung cancer (NSCLC). This meta-analysis was conducted to compare the clinical outcomes of IMRT and 3DCRT in the treatment of NSCLC.

Methods

No exclusions were made based on types of study design. We performed a literature search in PubMed, EMBASE and the Cochrane library databases from their inceptions to April 30, 2015. The overall survival (OS) and relative risk (RR) of radiation pneumonitis and radiation oesophagitis were evaluated. Two authors independently assessed the methodological quality and extracted data. Publication bias was evaluated by funnel plot using Egger’s test results.

Results

From the literature search, 10 retrospective studies were collected, and of those, 5 (12,896 patients) were selected for OS analysis, 4 (981 patients) were selected for radiation pneumonitis analysis, and 4 (1339 patients) were selected for radiation oesophagitis analysis. Cox multivariate proportional hazards models revealed that 3DCRT and IMRT had similar OS (HR = 0.96, P = 0.477) but that IMRT reduced the incidence of grade 2 radiation pneumonitis (RR = 0.74, P = 0.009) and increased the incidence of grade 3 radiation oesophagitis (RR = 2.47, P = 0.000).

Conclusions

OS of IMRT for NSCLC is not inferior to that of 3DCRT, but IMRT significantly reduces the risk of radiation pneumonitis and increases the risk of radiation oesophagitis compared to 3DCRT.

Dosimetric evaluation of a simple planning method for improving intensity-modulated radiotherapy for stage III lung cancer

This study aimed to evaluate the dosimetric outcomes of a base-dose-plan-compensation (BDPC) planning method for improving intensity-modulated radiotherapy (IMRT) for stage III lung cancer. For each of the thirteen included patients, three types of planning methods were applied to obtain clinically acceptable plans: (1) the conventional optimization method (CO); (2) a split-target optimization method (STO), in which the optimization objectives were set higher dose for the target with lung density; (3) the BDPC method, which compensated for the optimization-convergence error by further optimization based on the CO plan. The CO, STO and BDPC methods were then compared regarding conformity index (CI), homogeneity index (HI) of the target, organs at risk (OARs) sparing and monitor units (MUs). The BDPC method provided better HI/CI by 54%/7% on average compared to the CO method and by 38%/3% compared to the STO method. The BDPC method also spared most of the OARs by up to 9%. The average MUs of the CO, STO and BDPC plans were 890, 937 and 1023, respectively. Our results indicated that the BDPC method can effectively improve the dose distribution in IMRT for stage III lung cancer, at the expense of more MUs.

IMRT and 3D conformal radiotherapy with or without elective nodal irradiation in locally advanced NSCLC: A direct comparison of PET-based treatment planning

AIM

The potential of intensity-modulated radiation therapy (IMRT) as opposed to three-dimensional conformal radiotherapy (3D-CRT) is analyzed for two different concepts of fluorodeoxyglucose positron emission tomography (FDG PET)-based target volume delineation in locally advanced non-small cell lung cancer (LA-NSCLC): involved-field radiotherapy (IF-RT) vs. elective nodal irradiation (ENI).

METHODS

Treatment planning was performed for 41 patients with LA-NSCLC, using four different planning approaches (3D-CRT-IF, 3D-CRT-ENI, IMRT-IF, IMRT-ENI). ENI included a boost irradiation after 50 Gy. For each plan, maximum dose escalation was calculated based on prespecified normal tissue constraints. The maximum prescription dose (PD), tumor control probability (TCP), conformal indices (CI), and normal tissue complication probabilities (NTCP) were analyzed.

RESULTS

IMRT resulted in statistically significant higher prescription doses for both target volume concepts as compared with 3D-CRT (ENI: 68.4 vs. 60.9 Gy, p < 0.001; IF: 74.3 vs. 70.1 Gy, p < 0.03). With IMRT-IF, a PD of at least 66 Gy was achieved for 95 % of all plans. For IF as compared with ENI, there was a considerable theoretical increase in TCP (IMRT: 27.3 vs. 17.7 %, p < 0.00001; 3D-CRT: 20.2 vs. 9.9 %, p < 0.00001). The esophageal NTCP showed a particularly good sparing with IMRT vs. 3D-CRT (ENI: 12.3 vs. 30.9 % p < 0.0001; IF: 15.9 vs. 24.1 %; p < 0.001).

CONCLUSION

The IMRT technique and IF target volume delineation allow a significant dose escalation and an increase in TCP. IMRT results in an improved sparing of OARs as compared with 3D-CRT at equivalent dose levels.

Simultaneously modulated accelerated radiation therapy reduces severe oesophageal toxicity in concomitant chemoradiotherapy of locally advanced non-small-cell lung cancer

OBJECTIVE

The aim of this study was to evaluate the potential of simultaneously modulated accelerated radiation therapy (SMART) to reduce the incidence of severe acute oesophagitis in the treatment of unresectable locally advanced non-small-cell lung cancer (LANSCLC).

METHODS

21 patients were treated with SMART and concomitant platinum-based chemotherapy. The prescribed doses were limited to 54 Gy at 1.8 Gy per day to the zones of presumed microscopic extent while simultaneously maintaining doses of 66 Gy at 2.2 Gy per day to the macroscopic disease. The whole treatment was delivered over 30 fractions and 6 weeks. Dosimetric parameters of SMART and the standard technique of irradiation [intensity-modulated radiation therapy (IMRT)] were compared. Acute toxicity was prospectively recorded.

RESULTS

The highest grade of oesophagitis was 62% (13 patients) grade 1, 33% (7 patients) grade 2 and 5% (1 patient) grade 3. Three (14%) patients experienced acute grade 2 pneumonitis. There was no grade 4 oesophageal or pulmonary toxicity. Doses to the organs at risk were significantly reduced in SMART compared with IMRT [oesophagus: V50Gy, 28.5 Gy vs 39.9 Gy (p = 0.003); V60Gy, 7.1 Gy vs 30.7 Gy (p = 0.003); lung: V20Gy, 27.4 Gy vs 30.1 Gy (p = 0,002); heart: V40Gy, 7.3 Gy vs 10.7 Gy (p = 0.006); spine: Dmax, 42.4 Gy vs 46.4 Gy (p = 0.003)]. With a median follow-up of 18 months (6-33 months), the 1-year local control rate was 70% and the disease-free survival rate was 47%.

CONCLUSION

SMART reduces the incidence of severe oesophagitis and improves the whole dosimetric predictors of toxicity for the lung, heart and spine.

ADVANCES IN KNOWLEDGE

Our study shows that SMART optimizes the therapeutic ratio in the treatment of LANSCLC, opening a window for dose intensification.

Dose distribution and tumor control probability in out-of-field lymph node stations in intensity modulated radiotherapy (IMRT) vs 3D-conformal radiotherapy (3D-CRT) of non-small-cell lung cancer: an in silico analysis

Background

The advent of IMRT and image-guided radiotherapy (IGRT) in combination with involved-field radiotherapy (IF-RT) in inoperable non-small-cell lung cancer results in a decreased incidental dose deposition in elective nodal stations. While incidental nodal irradiation is considered a relevant by-product of 3D-CRT to control microscopic disease this planning study analyzed the impact of IMRT on dosimetric parameters and tumor control probabilities (TCP) in elective nodal stations in direct comparison with 3D-CRT.

Methods and materials

The retrospective planning study was performed on 41 patients with NSCLC (stages II-III). The CTV was defined as the primary tumor (GTV + 3 mm) and all FDG-PET-positive lymph node stations. As to the PTV (CTV + 7 mm), both an IMRT plan and a 3D-CRT plan were established. Plans were escalated until the pre-defined dose-constraints of normal tissues (spinal cord, lung, esophagus and heart) were reached. Additionally, IMRT plans were normalized to the total dose of the corresponding 3D-CRT. For two groups of out-of-field mediastinal node stations (all lymph node stations not included in the CTV (LN_{all_el}) and those directly adjacent to the CTV (LN_{adj_el})) the equivalent uniform dose (EUD) and the TCP (for microscopic disease a D50 of 36.5 Gy was assumed) for the treatment with IMRT vs 3D-CRT were calculated.

Results

In comparison, a significantly higher total dose for the PTV could be achieved with the IMRT planning as opposed to conventional 3D-CRT planning (74.3 Gy vs 70.1 Gy; p = 0.03). In identical total reference doses, the EUD of LN_{adj_el} is significantly lower with IMRT than with 3D-CRT (40.4 Gy vs. 44.2 Gy. P = 0.05) and a significant reduction of TCP with IMRT vs 3D-CRT was demonstrated for LN_{all_el} and LN_{adj_el} (12.6 % vs. 14.8 %; and 23.6 % vs 27.3 %, respectively).

Conclusions

In comparison with 3D-CRT, IMRT comes along with a decreased EUD in out-of-field lymph node stations. This translates into a statistically significant decrease in TCP-values. Yet, the combination of IF-RT and IMRT leads to a significantly better sparing of normal tissues and higher total doses whereas the potential therapeutic drawback of decreased incidental irradiation of elective lymph nodes is moderate.

Lung cancer. Radiotherapy in lung cancer: Actual methods and future trends

This survey is performed to update knowledge about methods and trends in lung cancer radiotherapy. A significant development has been noticed in radiotherapeutic techniques, but also in the identification of clinical prognostic factors. The improvement in the therapeutic line includes: application of the four-dimensional computer tomography (4DCT), taking advantage of positron emission tomography (PET-CT), designing of new computational algorithms, allowing more precise irradiation planning, development of treatment precision verification systems and introducing IMRT techniques in chest radiotherapy. The treatment outcomes have improved with high dose radiotherapy, but other fractionation alternations have been investigated as well.

An isotoxic planning comparison study for stage II-III non-small cell lung cancer: is intensity-modulated radiotherapy the answer?

AIMS

Recent clinical series suggest that treating patients with isotoxic twice-daily radiotherapy may be beneficial. This dosimetric planning study compared the use of intensity-modulated radiotherapy (IMRT) and three-dimensional conformal radiotherapy (3DRT) to deliver isotoxic treatment for non-small cell lung cancer (NSCLC) patients.

MATERIALS AND METHODS

Twenty patients with stage II/III NSCLC were selected. A dose-escalated plan was produced retrospectively for each using three different methods: (i) three to five beams 3DRT; (ii) seven beams inverse-planned conformal radiotherapy; (iii) seven beams IMRT. The starting point for dose escalation was 55.8 Gy in 1.8 Gy per fraction twice-daily. The number of fractions was then increased until one or more organ at risk tolerance dose was exceeded or a maximum dose of 79.2 Gy was reached.

RESULTS

The median escalated doses were 70.2, 66.6 and 64.8 Gy for IMRT, 3DRT and inverse-planned conformal radiotherapy, respectively. IMRT allowed a significant dose increase in comparison with the other two methods (P < 0.05), whereas no significant difference was found between 3DRT and inverse-planned conformal radiotherapy. IMRT was more successful at escalating dose in patients where the brachial plexus and spinal canal were close to the planning target volume. IMRT did not allow the escalation of dose beyond 70.2 Gy (82.8 Gy BED10, 69 Gy EQD2) due to the proximity of disease to the great vessels and the proximal bronchial tree.

CONCLUSIONS

IMRT allows increased dose escalation compared with conformal radiotherapy. However, there is limited opportunity to escalate the prescription dose beyond 70.2 Gy twice-daily in disease close to the central mediastinal structures.

Hyperfractionated and accelerated radiotherapy in non-small cell lung cancer

Radical radiotherapy plays a major role in the treatment of non-small cell lung cancer (NSCLC) due to the fact that many patients are medically or surgically inoperable. Advances in technology and radiotherapy delivery allow targeted treatment of the disease, whilst minimizing the dose to organs at risk. This in turn creates an opportunity for dose escalation and the prospect of tailoring radiotherapy treatment to each patient. This is especially important in patients deemed unsuitable for chemotherapy or surgery, where there is a need to increase the therapeutic gain from radical radiotherapy alone. Recent research into fractionation schedules, with hyperfractionated and accelerated radiotherapy regimes has been promising. How to combine these new fractionated schedules with dose escalation and chemotherapy remains open to debate and there is local, national and international variation in management with a lack of overall consensus. An overview of the current literature on hyperfractionated and accelerated radiotherapy in NSCLC is provided.

Strategies of dose escalation in the treatment of locally advanced non-small cell lung cancer: image guidance and beyond

Radiation dose in the setting of chemo-radiation for locally advanced non-small cell lung cancer (NSCLC) has been historically limited by the risk of normal tissue toxicity and this has been hypothesized to correlate with the poor results in regard to local tumor recurrences. Dose escalation, as a means to improve local control, with concurrent chemotherapy has been shown to be feasible with three-dimensional conformal radiotherapy in early phase studies with good clinical outcome. However, the potential superiority of moderate dose escalation to 74 Gy has not been shown in phase III randomized studies. In this review, the limitations in target volume definition in previous studies; and the factors that may be critical to safe dose escalation in the treatment of locally advanced NSCLC, such as respiratory motion management, image guidance, intensity modulation, FDG-positron emission tomography incorporation in the treatment planning process, and adaptive radiotherapy, are discussed. These factors, along with novel treatment approaches that have emerged in recent years, are proposed to warrant further investigation in future trials in a more comprehensive and integrated fashion.

[New techniques in thoracic radiation therapy]

Advanced technologies have led to an improvement of target volume delineation and a higher accuracy in dose delivery. Stereotactic body radiotherapy, intensity-modulated radiotherapy and respiratory gating allow new therapeutic perspectives along with an improvement of the therapeutic ratio. Ongoing trials aim to show the magnitude of gains in patient care with technical improvements.

Inhomogeneous dose escalation increases expected local control for NSCLC patients with lymph node involvement without increased mean lung dose

BACKGROUND

Higher doses to NSCLC tumours are required to increase the low control rates obtained with conventional dose prescriptions. This study presents the concept of inhomogeneous dose distributions as a general way to increase local control probability, not only for isolated lung tumours but also for patients with involved lymph nodes.

MATERIAL AND METHODS

Highly modulated IMRT plans with homogeneous dose distributions with a prescribed dose of 66Gy/33F were created for 20 NSCLC patients, staged T1b-T4 N0-N3, using standard PTV dose coverage of 95-107%. For each patient, an inhomogeneous dose distribution was created with dose constraints of: PTV-coverage ≥ 95%, same mean lung dose as obtained in the homogeneous dose plan, maximum doses of 45 and 66 Gy to spinal canal and oesophagus, respectively, and V74Gy < 1 cm(3) for each of: aorta, trachea + bronchi, the connective tissue in mediastinum, and the thorax wall. The dose was escalated using a TCP model implemented into the planning system. The difference in TCP values between the homogeneous and inhomogeneous plans were evaluated using two different TCP models.

RESULTS

Dose escalation was possible for all patients. TCP values based on assumed homogeneous distribution of clonogenic cells either in the GTV, CTV or PTV showed absolute TCP increases of approximately 15, 10 and 5 percentage points, respectively. This increase in local control was obtained without increasing the mean lung dose. However, small increases in maximum doses to the mediastinum were observed: 2.5 Gy for aorta, 4.4 Gy for the connective tissue, 1.6 Gy for the heart, and 2.6 Gy for trachea + bronchi.

CONCLUSION

Increased target doses and TCP values using inhomogeneous dose distributions could be achieved for all patients, regardless of lymph node involvement, tumour stage, location, and size. These new treatment plans have the potential to increase the local tumour control by 10-15 percentage points without compromising the clinically acceptable lung toxicity level.

New radiotherapy approaches in locally advanced non-small cell lung cancer

Radiotherapy plays a major role in the treatment of patients with locally advanced non-small cell lung cancer (NSCLC), particularly since most patients are not suitable for surgery due to the extent of their disease, advanced age and multiple co-morbidities. Despite advances in local and systemic therapies local control and survival remain poor and there is a sense that a therapeutic plateau has been reached with conventional approaches. Strategies for the intensification of radiotherapy such as dose escalation have shown encouraging results in phase I-II trials, but the outcome of the phase III Radiation Therapy Oncology Group 0617 trial was surprisingly disappointing. Hyperfractionated and/or accelerated fractionating schedules have demonstrated superior survival compared to conventional fractionation at the expense of greater oesophageal toxicity. Modern radiotherapy techniques such as the integration of 4-dimensional computed tomography for planning, intensity modulated radiotherapy and image-guided radiotherapy have substantially enhanced the accuracy of the radiotherapy delivery through improved target conformality and incorporation of tumour respiratory motion. A number of studies are evaluating personalised radiation treatment including the concept of isotoxic radiotherapy and the boosting of the primary tumour based on functional imaging. Proton beam therapy is currently under investigation in locally advanced NSCLC. These approaches, either alone or in combination could potentially allow for further dose escalation and improvement of the therapeutic ratio and survival for patients with NSCLC.

How can we optimise concurrent chemoradiotherapy for inoperable stage III non-small cell lung cancer?

Latest evidence sets a clear mandate for concurrent chemoradiotherapy as the current standard of care for inoperable stage III non small cell lung cancer patients with good performance status and minimal co-morbidities. However, a survival plateau has been reached, with disappointing results from dose escalation studies using conventional fractionation and studies investigating the addition of systemic doses of chemotherapy delivered before or after concurrent chemoradiotherapy. A review was carried out to address three questions considered fundamental to improving outcome in patients with stage III non-small cell lung cancer: (1) Can radiotherapy regimens be optimised using advanced radiotherapy techniques to improve local control rate and overall survival? (2) Can systemic therapy regimens be optimised to reduce the risk of distant metastases? (3) Should concurrent chemoradiotherapy be considered standard of care for locally advanced non-small cell lung cancer in the elderly? It is clear that further improvement in outcome for these patients will be determined by better local control and by reducing the risk of distant recurrence. Given the technological advances in radiotherapy planning and delivery in recent years plus the abundance of novel targeted therapies exploiting critical oncogenic pathways, further advances in combined drug-radiation treatment for lung cancer seem highly possible.

Dose escalation for locally advanced lung cancer using adaptive radiation therapy with simultaneous integrated volume-adapted boost

PURPOSE

To test the feasibility of a planned phase 1 study of image-guided adaptive radiation therapy in locally advanced lung cancer.

METHODS AND MATERIALS

Weekly 4-dimensional fan beam computed tomographs (4D FBCT) of 10 lung cancer patients undergoing concurrent chemoradiation therapy were used to simulate adaptive radiation therapy: After an initial intensity modulated radiation therapy plan (0-30 Gy/2 Gy), adaptive replanning was performed on week 2 (30-50 Gy/2 Gy) and week 4 scans (50-66 Gy/2 Gy) to adjust for volume and shape changes of primary tumors and lymph nodes. Week 2 and 4 clinical target volumes (CTV) were deformably warped from the initial planning scan to adjust for anatomical changes. On the week 4 scan, a simultaneous integrated volume-adapted boost was created to the shrunken primary tumor with dose increases in 5 0.4-Gy steps from 66 Gy to 82 Gy in 2 scenarios: plan A, lung isotoxicity; plan B, normal tissue tolerance. Cumulative dose was assessed by deformably mapping and accumulating biologically equivalent dose normalized to 2 Gy-fractions (EQD2).

RESULTS

The 82-Gy level was achieved in 1 in 10 patients in scenario A, resulting in a 13.4-Gy EQD2 increase and a 22.1% increase in tumor control probability (TCP) compared to the 66-Gy plan. In scenario B, 2 patients reached the 82-Gy level with a 13.9 Gy EQD2 and 23.4% TCP increase.

CONCLUSIONS

The tested image-guided adaptive radiation therapy strategy enabled relevant increases in EQD2 and TCP. Normal tissue was often dose limiting, indicating a need to modify the present study design before clinical implementation.

Prescribing radiation dose to lung cancer patients based on personalized toxicity estimates

INTRODUCTION

The lung radiosensitivity of the most sensitive patients limits doses that can be given to the majority of lung cancer patients. The purpose of the current study was to illustrate the concept of personalizing prescription dose by performing a retrospective study in which the prescription is determined using an individualized dose-volume constraint that is calculated from a toxicity prediction model. We test whether using a model-generated personalized lung-dose limit results in a clinically significant change to the prescription.

METHODS

A model consisting of a dose-volume component and a genetic component (single-nucleotide polymorphism information) was used to determine iso-risk mean lung-dose (MLD) limits for each patient. The prescription dose for each patient was scaled according to the individualized MLD constraint and population-based constraints for the cord, esophagus, and heart. The difference between the model-determined prescription dose and the prescription the patient was originally treated with was evaluated.

RESULTS

For 59% of the patients the change in prescription using the model-determined limit was greater than 5 Gy (either dose escalation or de-escalation). For 96% of the patients who developed radiation pneumonitis the model predicted that the prescription should have been lowered.

CONCLUSIONS

Our results indicate that using a model-generated personalized MLD results in a clinically different (≥ 5 Gy) prescription. A model used in the manner described by the study can help physicians further personalize radiation therapy and aid them in determining how much dose can safely be delivered to the tumor and normal tissues.

How important is dosimetrist experience for intensity modulated radiation therapy? A comparative analysis of a head and neck case

PURPOSE

Treatment planning for IMRT is a complex process that requires additional training and expertise. The aim of this study was to compare and analyze IMRT plans generated by dosimetrists with varying levels of IMRT planning experience.

METHODS AND MATERIALS

The computed tomography (CT) data of a patient previously treated with IMRT for left tonsillar carcinoma were used. The patient's preexisting planning target volumes (PTVs) and all organs at risk were provided with the CT data set. Six dosimetrists with variable IMRT planning experience generated IMRT plans according to the department's protocol. Plan analysis included visual inspection and comparison of dose-volume histogram, conformity indices, treatment delivery efficiency, and dose delivery accuracy.

RESULTS

Visual review of the dose distribution showed that the 6 plans were comparable. However, only the 2 most experienced dosimetrists were able to meet the strict PTV aims and critical structure constraints. The least experienced dosimetrist had the worst planning outcome. Comparison of delivery efficiency showed that the number of segments, total monitor units, and treatment time increased as the IMRT planning experience decreased.

CONCLUSIONS

Dosimetrists with higher levels of IMRT planning experience produced a better quality head and neck IMRT plan. Different planning experience may need to be considered when organizing appropriate departmental resources.

AP-PA field orientation followed by IMRT reduces lung exposure in comparison to conventional 3D conformal and sole IMRT in centrally located lung tumors

Little attention has been paid to the fact that intensity modulated radiation therapy (IMRT) techniques do not easily enable treatment with opposed beams. Three treatment plans (3 D conformal, IMRT, and combined (anterior-posterior-posterio-anterior (AP-PA) + IMRT) of 7 patients with centrally-located lung cancer were compared for exposure of lung, spinal cord and esophagus. Combined IMRT and AP-PA techniques offer better lung tissue sparing compared to plans predicated solely on IMRT for centrally-located lung tumors.

Intensity modulated radiation therapy (IMRT) for the treatment of unicentric Castlemans disease: a case report and review of the use of radiotherapy in the literature

Background

Surgical resection is considered standard therapy for cases of resectable unicentric Castleman’s disease (UCD). Unresectable cases of UCD do not have a consensus regarding the optimal treatment approach, but have utilized steroids, observation, chemotherapy, and radiotherapy. Here we discuss a patient presentation of UCD treated with an advanced radiotherapy technique, IMRT.

Case report

A 47 year old female was found to have an intra-thoracic posterior UCD and was determined not to be a good surgical candidate. She was referred for radiotherapy and was treated using IMRT to a total dose of 4320 cGy in 180 cGy fractions including a scheduled 10 day break. Following the break, the patient’s treatment was replanned at which the initial treatment volume was reduced by 50.9% for the duration of the treatment course. Radiation Therapy Oncology Group (RTOG) grade III pneumonitis developed which was managed medically. Neither disease progression nor late effects have occurred.

Conclusions

The use of IMRT and planned treatment break was successful in the treatment of a case of UCD, and should be considered for other unresectable cases.

Radiation Dose Escalation in Stage III Non-Small-Cell Lung Cancer

For patients with stage III non-small-cell lung cancer with unresectable or inoperable tumors, definitive chemoradiotherapy is often utilized. Historically, local control and overall survival rates have been poor. In an effort to improve local control, new chemotherapeutic agents in combination with higher doses of radiotherapy have been investigated. Early dose escalation trials date back to the 1980s, and the feasibility and efficacy of dose escalation for patients with inoperable stage III lung cancer continue to be topics of investigation. Herein, we review the evolution of chemotherapy as it relates to treatment of unresectable stage III lung cancer, and we outline the early and the more recent dose escalation studies. While dose escalation appears to provide a modest benefit in terms of preventing local failure and improving overall survival, advances in diagnostic imaging and radiotherapy treatment have possibly resulted in selection of a more favorable patient population. These variables make statements regarding the benefit of dose escalation challenging.