Intensity-modulated radiotherapy and volumetric-modulated arc therapy have distinct clinical advantages in non-small cell lung cancer treatment

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.

Intensity-modulated proton and carbon-ion radiotherapy using a fixed-beam system for locally advanced lung cancer: dosimetric comparison with x-ray radiotherapy and normal tissue complication probability (NTCP) evaluation

Objective. To assess the dosimetric consequences and the normal tissue complication probability (NTCP) for the organs at risk (OARs) in intensity-modulated particle radiotherapy of proton (IMPT) and carbon-ion (IMCT) using a fixed-beam delivery system when compared with intensity-modulated photon radiotherapy (IMRT) for locally advanced small-cell lung cancer.Approach. The plans were all designed under the same total relative biological effectiveness (RBE)-weighted prescription dose, in which the planning target volume (PTV) of the internal gross target volume(IGTV) and the PTV of the clinical target volume was irradiated with 69.3 Gy (RBE) and 63 Gy (RBE), respectively, using a simultaneously integrated boosting (SIB) technique. NTCPs were estimated for heart, lung, esophagus and spinal cord by Lyman-Kutcher-Burman (LKB) and logistic models. Dose escalation was simulated under the desired NTCP values (0.05, 0.10 and 0.50) of the three radiation techniques.Main results. Under the similar target coverage, almost all OARs were significantly better spared (p< 0.05) when using the particle radiotherapy except for D1cc (the dose to 1 cm3of the volume) of the proximal bronchial tree (p> 0.05). At least 57.6% of mean heart dose, 28.8% of mean lung dose and 19.1% of mean esophageal dose were reduced compared with IMRT. The mean NTCP of radiation-induced pneumonitis (RP) in the ipsilateral lung was 0.39 ± 0.33 (0.39 ± 0.31) in IMPT plans and 0.36 ± 0.32 (0.35 ± 0.30) in IMCT plans compared with 0.66 ± 0.30 (0.64 ± 0.28) in IMRT plans by LKB (logistic) models. The target dose could be escalated to 78.3/76.9 Gy (RBE) in IMPT/IMCT plans compared with 61.7 Gy (RBE) in IMRT plans when 0.50 of NTCP in terms of RP in the ipsilateral lung was applied.Significance. This study presents the potential of better control of the side effects and improvement of local control originating from the dosimetric advantage with the application of IMPT and IMCT with the SIB technique for locally advanced lung cancer, even with limited beam directions.

Comparison of photon intensity modulated, hybrid and volumetric modulated arc radiation treatment techniques in locally advanced non-small cell lung cancer

Background and purpose

There is no consensus on the best photon radiation technique for non-small cell lung cancer (NSCLC). This study quantified the differences between commonly used treatment techniques in NSCLC to find the optimal technique.

Materials and methods

Treatment plans were retrospectively generated according to clinical guidelines for 26 stage III NSCLC patients using intensity modulated radiation therapy (IMRT), hybrid, and volumetric modulated arc therapy (VMATC, and VMATV5 optimized for lower lung and heart dose). Plans were evaluated for target coverage, organs at risk dose (including heart substructures) and normal tissue complication probabilities (NTCP).

Results

The comparison showed significant and largest median differences (>1 Gy or >5%) in favor of IMRT for the mediastinal envelope and heart (maximum dose), in favor of the hybrid technique for the lungs (V5Gy of the total lungs and V5Gy of the contralateral lung) and in favor of VMATC for the heart (Dmean), most of the substructures of the heart, and the spinal cord (maximum dose). The VMATV5 technique had significantly lower heart dose compared to the hybrid technique and significantly lower lung dose compared to the VMATC, combining both advantages in one technique. The mean ΔNTCP did not exceed the 2 percent point (pp) for grade 5 (mortality), and 10 pp for grade ≥2 toxicities (radiation pneumonitis and acute esophageal toxicity), but ΔNTCP was mostly in favor of VMATC/V5 for individual patients.

Conclusion

This planning study showed that VMATV5 was preferred as it achieved low lung and heart doses, as well as low NTCPs, simultaneously.

Optimal beam angle selection and knowledge-based planning significantly reduces radiotherapy dose to organs at risk for lung cancer patients

BACKGROUND

Lung cancer patients struggle with high toxicity rates. This study investigates if IMRT plans with individually set beam angles or uni-lateral VMAT plans results in dose reduction to OARs. We investigate if introduction of a RapidPlan model leads to reduced dose to OARs. Finally, the model is validated prospectively.

MATERIAL AND METHODS

Seventy-four consecutive lung cancer patients treated with IMRT were included. For all patients, new IMRT plans were made by an experienced dose planner re-tuning beam angles aiming for minimized dose to the lungs and heart. Additionally, VMAT plans were made. The IMRT plans were selected as input for a RapidPlan model, which was used to generate 74 new IMRT plans. The new IMRT plans were used as input for a second RapidPlan model. This model was clinically implemented and used for generation of clinical treatment plans. Dosimetric parameters were compared using a Wilcoxon signed rank test or a 1-sided student's t-test. p < .05 was considered significant.

RESULTS

IMRT plans significantly reduced mean doses to lungs (MLD) and heart (MHD) by 1.6 Gy and 1.7 Gy in mean compared to VMAT plans. MLD was significantly (p < .001) reduced from 10.8 Gy to 9.4 Gy by using the second RapidPlan model. MHD was significantly (p < .001) reduced from 4.9 Gy to 3.9 Gy. The model was validated in prospectively collected treatment plans showing significantly lower MLD after the implementation of the second RapidPlan model.

CONCLUSION

Introduction of RapidPlan and beam angles selected based on the target and OARs position reduces dose to OARs.

Toxicity after volumetric modulated arc therapy for lung cancer: a monocentric retrospective study

Background

Intensity-modulated radiotherapy (RT) is now widely implemented and has replaced classical three-dimensional (3D)-RT in many tumor sites, as it allows a better target dose conformity and a better sparing of organs a risk (OAR), at the expense, however, of increasing the volume of low dose to normal tissues. Clinical data on toxicities using volumetric modulated arc therapy (VMAT) in lung cancer remain scarce. We aimed to report both acute (APT) and late (LPT) pulmonary and acute (AET) and late (LET) oesophageal toxicities in such setting.

Methods

All patients treated for a primary lung cancer with VMAT +/- chemotherapy (ChT) in our center from 2014 to 2018 were retrospectively included. Usual clinical, treatment and dosimetric features were collected. Univariate analysis was performed using the receiver operative characteristics approach while multivariate analysis (MVA) relied on logistic regression, calculated with Medcalc 14.8.1.

Results

In total, 167 patients were included, with a median age of 66 years (39-88 years). Median radiation dose was 66 Gy (30-66 Gy); 82% patients received concomitant (32.3%), induction (25.7%) or induction followed by concomitant ChT (24%). After a median follow-up of 14.0 months, the G ≥2 APT, AET, LPT and LET rates were 22.2%, 30.0%, 16.8% and 5.4%, respectively with low grade ≥3 toxicity rates (respectively, 3%, 6.6%, 3% and 0%). On MVA, APT was significantly associated with V30 to the homolateral lung, AET with age, LPT with MEVS while no feature remained significantly correlated with LET.

Conclusions

Low rates of pulmonary and esophageal toxicity were observed in our cohort. Larger prospective studies are needed to confirm these results.

Rationale for concurrent chemoradiotherapy for patients with stage III non-small-cell lung cancer

When treating patients with unresectable stage III non-small-cell lung cancer (NSCLC), those with a good performance status and disease measured within a radical treatment volume should be considered for definitive concurrent chemoradiotherapy (cCRT). This guidance is based on key scientific rationale from two large Phase 3 randomised studies and meta-analyses demonstrating the superiority of cCRT over sequential (sCRT). However, the efficacy of cCRT comes at the cost of increased acute toxicity versus sequential treatment. Currently, there are several documented approaches that are addressing this drawback, which this paper outlines. At the point of diagnosis, a multidisciplinary team (MDT) approach can enable accurate assessment of patients, to determine the optimal treatment strategy to minimise risks. In addition, reviewing the Advisory Committee on Radiation Oncology Practice (ACROP) guidelines can provide clinical oncologists with additional recommendations for outlining target volume and organ-at-risk delineation for standard clinical scenarios in definitive cCRT (and adjuvant radiotherapy). Furthermore, modern advances in radiotherapy treatment planning software and treatment delivery mean that radiation oncologists can safely treat substantially larger lung tumours with higher radiotherapy doses, with greater accuracy, whilst minimising the radiotherapy dose to the surrounding healthy tissues. The combination of these advances in cCRT may assist in creating comprehensive strategies to allow patients to receive potentially curative benefits from treatments such as immunotherapy, as well as minimising treatment-related risks.

Intensity-modulated radiation therapy versus volumetric-modulated arc therapy in non-small cell lung cancer: assessing the risk of radiation pneumonitis

Purpose

This study aimed to compare intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT) regarding plan quality and healthy lung sparing, in stage III non-small cell lung cancer (NSCLC) patients.

Materials and methods

The plans of 60 patients were allocated either to the IMRT (n=30) or the VMAT (n=30) group. The dose prescribed to the planning target volume (PTV) was evaluated at the 95% level and the mean lung dose (MLD) and the healthy lung receiving 5, 10 and 20 Gy (V5, V10and V20, respectively) were analysed. The normal tissue complication probability (NTCP) for radiation pneumonitis was calculated with the Lyman–Kutcher–Burman model.

Results

Both techniques achieved comparable results for target coverage (V95%=97·87 versus 97·18%,p>0·05) and homogeneity. The MLD (15·57 versus 16·98 Gy,p>0·05), V5(60·35 versus 67·25%,p>0·05) and V10(45·22 versus 53·14%,p=0·011) were lower for IMRT, whereas VMAT reduced V20(26·44 versus 25·90%,p>0·05). The NTCP for radiation pneumonitis was higher for VMAT, but no statistical significance was observed (11·07 versus 12·75,p>0·05).

Conclusion

Both techniques seemed suitable for NSCLC treatment, but IMRT presented better results regarding lung sparing thus being beneficial in reducing the risk of radiation-induced pneumonitis.

Evaluation of MLC leaf transmission on IMRT treatment plan quality of patients with advanced lung cancer

The purpose of this paper was to evaluate the impact of leaf treatment of multileaf collimator (MLC) in plan quality of intensity-modulated radiotherapy (IMRT) of patients with advanced lung cancer. Five MLCs with different leaf transmissions (0.01%, 0.5%, 1.2%, 1.8%, and 3%) were configured for an accelerator in a treatment planning system. Correspondingly, 5 treatment plans with the same optimization setting were created and evaluated quantitatively for each patient (11 patients total) who was diagnosed with advanced lung cancer. All of the 5 plans for each patient met the dose requirement for the planning treatment volumes (PTVs) and had similar target dose homogeneity and conformity. On average, the doses to selected organs were as follows: (1) V₅, V₂₀, and the mean dose of total lung; (2) the maximum and mean dose to spinal cord planning organ-at-risk volume (PRV); and (3) V₃₀ and V₄₀ of heart, decreased slightly when MLC transmission was decreased, but with no statistical differences. There is a clear grouping of plans having total quality score (S_D) value, which is used to evaluate plan quality: (1) more than 1 (patient nos. 1 to 3, 5, and 8), and more than 2.5 (patient no. 6); (2) less than 1 (patient nos. 7 and 10); (3) around 1 (patient nos. 4, 9, and 11). As MLC transmission increased, overall S_D values increased as well and plan dose requirement was harder to meet. The clinical requirements were violated increasingly as MLC transmission became large. Total S_D with and without normal tissue (NT) showed similar results, with no statistically significant differences. Therefore, decrease of MLC transmission did have minimum impact on plan, and it improved target coverage and reduced normal tissue radiation slightly, with no statistical significance. Plan quality could not be significantly improved by MLC transmission reduction. However, lower MLC transmission may have advantages on lung sparing to low- and intermediate-dose exposure. Besides conventional fraction, hyperfraction, or stereotactic body radiotherapy (SBRT), the reduction on lung sparing is still essential because it is highly relevant to radiation pneumonitis (RP). It has potential to diminish incidence of RP and improve patient's quality of life after irradiation with lowered MLC transmission.

Association between clinicopathological factors and postoperative radiotherapy in patients with completely resected pathological N2 non-small cell lung cancer

The function of postoperative radiotherapy (PORT) in patients with completely resected pathologically N2 (pN2) non-small cell lung cancer (NSCLC) remains controversial due to a lack of prospective studies. The present study aimed to evaluate the efficacy of PORT in completely resected pN2 NSCLC when using modern radiation techniques, and to determine the associations between clinicopathological factors and PORT and survival rates. Following patient selection, 246 out of 269 consecutive patients with pN2 NSCLC were enrolled in the present study, with 88 patients having received postoperative chemotherapy (POCT) and PORT, 90 having received adjuvant chemotherapy, 1 having received adjuvant radiotherapy and the remaining 67 having received no adjuvant therapy. Overall survival (OS), local recurrence-free survival (LRFS) and disease-free survival (DFS) were estimated using the Kaplan-Meier method. The median age of the patients was 59 years, overall, 175 (71.1%) of the patients were male and the median radiation dose was 50.4 Gy. The median follow-up duration was 38.3 months. The 1-, 3- and 5-year OS rates were 98.9, 71.3 and 54.9%, and 93.0, 58.4 and 36.7% (P=0.011) in the PORT and non-PORT group, respectively. The 1-, 3- and 5-year LRFS rates were 95.5, 84.6 and 78.0%, and 86.6, 70.6 and 52.8% (P<0.001) in the PORT and non-PORT groups, respectively. The 1-, 3- and 5-year DFS rates were 86.5, 55.2 and 37.9%, and 80.9, 40.3 and 26.8% (P=0.132) in the PORT and non-PORT groups, respectively. Univariate analysis revealed that the OS rate was significantly increased in patients with peripheral tumors (P=0.029), pT1-2 (P=0.015), one N2 lymph node (LN) metastasis (P=0.001), single N2 station metastasis (P=0.030), no bronchial involvement (P=0.025), use of PORT (P=0.011) and POCT (P=0.003). Multivariate analysis revealed that PORT (HR, 0.755; 95% CI, 0.498-0.986; P=0.047), POCT (HR, 0.645; 95% CI, 0.420-0.988; P=0.044), bronchial involvement (HR, 1.453; 95% CI, 1.002-2.107; P=0.049) and ≥2 N2 metastases (HR, 1.969; 95% CI, 1.228-3.157; P=0.005) were significant independent predictors of OS. Subgroup analysis demonstrated an increased OS rate with PORT only in the patients with positive bronchial involvement and ≥2 N2 LN metastases. The results revealed that PORT may improve the LRFS and OS rates in completely resected pN2 NSCLC, and that the patients with positive bronchial involvement and ≥2 N2 LN metastases may receive more benefit from PORT.

Superior sulcus non-small cell lung carcinoma: A comparison of IMRT and 3D-RT dosimetry

AIM

A dosimetric study comparing intensity modulated radiotherapy (IMRT) by TomoTherapy to conformational 3D radiotherapy (3D-RT) in patients with superior sulcus non-small cell lung cancer (NSCLC).

BACKGROUND

IMRT became the main technique in modern radiotherapy. However it was not currently used for lung cancers. Because of the need to increase the dose to control lung cancers but because of the critical organs surrounding the tumors, the gains obtainable with IMRT is not still demonstrated.

MATERIAL AND METHODS

A dosimetric comparison of the planned target and organs at risk parameters between IMRT and 3D-RT in eight patients who received preoperative or curative intent irradiation.

RESULTS

In the patients who received at least 66 Gy, the mean V95% was significantly better with IMRT than 3D-RT (p = 0.043). IMRT delivered a lower D2% compared to 3D-RT (p = 0.043). The IH was significantly better with IMRT (p = 0.043). The lung V 5 Gy and V 13 Gy were significantly higher in IMRT than 3D-RT (p = 0.043), while the maximal dose (D max) to the spinal cord was significantly lower in IMRT (p = 0.043). The brachial plexus D max was significantly lower in IMRT than 3D-RT (p = 0.048). For patients treated with 46 Gy, no significant differences were found.

CONCLUSION

Our study showed that IMRT is relevant for SS-NSCLC. In patients treated with a curative dose, it led to a reduction of the exposure of critical organs, allowing a better dose distribution in the tumor. For the patients treated with a preoperative schedule, our results provide a basis for future controlled trials to improve the histological complete response by increasing the radiation dose.