Potential benefits of using non coplanar field and intensity modulated radiation therapy to preserve the heart in irradiation of lung tumors in the middle and lower lobes

doi:10.1016/j.radonc.2006.07.009

Radiotherapy and Oncology

Volume 80, Issue 3, September 2006, Pages 333-340

https://doi.org/10.1016/j.radonc.2006.07.009 Get rights and content

Abstract

Purpose

Investigate whether the use of non coplanar fields and intensity modulated radiation therapy (IMRT) reduces the dose to the heart, in irradiation of middle and lower lung tumors.

Materials and methods

Four plans are compared on 10 CT scans: (1) a reference plan, corresponding to coplanar plan of 3D conformal radiotherapy (3DCRT); (2) a 3DCRT_noncopl plan, differing from reference plan by the change of one field in non coplanar fields; (3) an IMRT_copl plan optimized on the same coplanar plan as reference plan; and (4) an IMRT_noncopl plan optimized on the same non coplanar beams as 3DCRT_noncopl plan. The equivalent uniform dose (EUD) for PTV was 74 Gy in 37 fractions.

Results

In all plans, the 95% isodose surface covers at least 99% of the PTV with very similar conformity index values. A significant reduction in EUD, V30, V40 and V50 is observed for heart when either non coplanar fields or IMRT is used. IMRT also reduces the lung NTCP, V5, V13, V20 and V30 values and esophagus NTCP.

Conclusion

Both the use of non coplanar fields and IMRT dramatically reduces the dose received by the heart. The largest benefit is seen when the two techniques are combined.

Section snippets

Patient selection

This study was performed using the treatment planning CT scans of 10 patients presented with stage IIIA or IIIB NSCLC. Because of the location of the target volume in the lower or middle lobes, the heart was one of the main organs at risk.

Plans of treatment

Two 3DCRT plans and two IMRT plans were generated, optimized and compared.

PTV coverage

In the four plans evaluated and for all the patients, the 95% isodose (70.3 Gy) covered at least 99% of the PTV volume. The maximum dose to the PTV did not exceed 107% of the prescribed dose in any of the plans. The mean gEUD values for the 10 cases were very comparable among the plans, with 73.7, 73.8, 73.5 and 73.6 Gy, respectively, for reference plans, 3DCRT_noncopl plans, IMRT_copl plans and IMRT_noncopl plans. The mean conformity index values were also very similar among the plans with 0.58 ±

Discussion

The first aim of this study was, to evaluate whether the use of intensity modulation and non coplanar fields could improve heart preservation in patients with lung tumors located in the middle or lower lobes of the lung. To our knowledge, this is the first investigation of this issue. It was assumed that an immobilization of the tumor was possible by applying a gating technique in order to allow a modulated intensity.

Few IMRT dosimetric studies have been published on the potential interest of

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Bien que la radiothérapie conformationnelle en trois dimensions (RC3D) reste la référence comme traitement à visée curative des carcinomes bronchiques non à petites cellules (CBNPC) lorsque la chirurgie n’est pas retenue, la radiothérapie conformationnelle avec modulation d’intensité (RCMI ou IMRT) est de plus en plus utilisée en routine. L’objectif de cette étude était d’évaluer l’impact clinique (toxicité immédiate) et dosimétrique de la RCMI par rapport à la radiothérapie conformationnelle en trois dimensions dans le traitement des cancers bronchiques non à petites cellules localement évolués (de stades IIIA à IIIC) pris en charge par chimioradiothérapie concomitante, alors que la RCMI était mise en place dans le cancer du poumon dans le département de radiothérapie du centre Jean-Perrin.
Entre mars 2015 et octobre 2019, 64 patients pris en charge par chimioradiothérapie concomitante ont été inclus rétrospectivement. Trente-deux ont bénéficié d’une conformationnelle en trois dimensions et 32 d’une RCMI. La prescription de radiothérapie était de 66 Gy en 33 fractions de 2 Gy.
La RCMI a permis une amélioration de la couverture des volumes cibles (volume recevant 95 % de la dose prescrite, V95, augmenté de 14,89 % en RCMI ; p < 0,001) sans augmentation des doses dans les organes à risque et une diminution des dysphagies (relative risk [RR] = 0,67 ; p = 0,027). Les faibles doses au poumon ont été non significativement augmentées en RCMI (volume recevant 5 % de la dose prescrite, V5 pulmonaire, augmenté de 7,46 % en RCMI).
La radiothérapie en modulation d’intensité permet, en comparaison à la technique standard en radiothérapie conformationnelle en trois dimensions, une amélioration dosimétrique de la couverture des volumes cibles sans augmenter la dose dans les organes à risque. Elle améliore également la tolérance immédiate du traitement en diminuant le nombre de dysphagies tous grades confondus.
Although three-dimensional conformal radiotherapy (3D-CRT) remains the gold standard as a curative treatment for NSCLC when surgery is not possible, intensity modulated radiotherapy (IMRT) is increasingly used routinely. The purpose of this study was to assess the clinical (immediate toxicities) and dosimetric impact of IMRT compared to 3D-CRT in the treatment of locally advanced (stages IIIA to IIIC) non-small cell lung cancer (NSCLC) treated with concomitant radiochemotherapy, while IMRT in lung cancer was implemented in the radiotherapy department of the Jean-Perrin Center.
Between March 2015 and October 2019, 64 patients treated with concomitant radiochemotherapy were retrospectively included. Thirty-two received 3D-CRT and 32 IMRT. The radiotherapy prescription was 66 Gy in 33 fractions of 2 Gy.
IMRT has improved coverage of target volumes (V95 increased by 14.81% in IMRT; P < 0.001) without increasing doses to OARs and reducing dysphagia (RR = 0.67; P = 0.027). Low doses to the lung were not significantly increased in IMRT (pulmonary V5 increased by 7.46% in IMRT).
Intensity modulated radiotherapy, compared with the standard RC3D technique, improve the coverage of target volumes without increasing the dose to the OARs. It also improves the immediate tolerance of the treatment by reducing the number of dysphagia.
A Comparison of Radiation Techniques in Patients Treated With Concurrent Chemoradiation for Stage III Non-Small Cell Lung Cancer
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Citation Excerpt :
By employing multiple intensity levels across a radiation beam from different angles or through a continuous arc, a more conformal dose distribution is achieved compared with conventional 3-dimensional conformal radiation therapy (3DCRT). The use of more advanced techniques in lung cancer treatment has been shown to be dosimetrically superior to 3DCRT by limiting high dose to organs at risk3-6 while allowing higher doses to be delivered to the target.7-9 The literature on the clinical benefit of these techniques in NSCLC is largely based on IMRT and mostly limited to retrospective series.
The standard of care in management of patients with good performance status and unresectable stage III non-small cell lung cancer (NSCLC) therapy is concurrent chemoradiation. Newer techniques such as intensity modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) are replacing 3-dimensional conformal radiation (3DCRT) despite low-quality evidence of improved outcomes. We used population-based data to examine survival outcomes by radiation technique.
A population-based retrospective cohort of patients with stage III NSCLC treated with concurrent chemoradiation from 2009 to 2017 in Ontario were identified. The primary outcome was a comparison of overall survival among 3DCRT, IMRT, and VMAT, calculated using the Kaplan-Meier method and compared using log-rank test. Cox regression was used to investigate effect of radiation type on overall survival adjusted for other covariates.
A total of 3872 patients were treated with 3DCRT (n = 1178), IMRT (n = 1847), or VMAT (n = 847). A decline in 3DCRT and increase in VMAT use were observed over time. Median survival in months was 21.2 (95% confidence interval [CI], 20.0-22.8) for 3DCRT, 23.9 (95% CI, 22.3-25.6) for IMRT, and 24.9 (95% CI, 22.5-27.4) for VMAT, but these differences were not statistically significant (P = .06).
Our study demonstrates that survival is not compromised in patients receiving IMRT or VMAT (compared with 3DCRT). Thus, given the potential dosimetric advantages associated with these techniques, VMAT and IMRT are recommended for the management of patients with stage III NSCLC.
Pitfalls and Challenges to Consider before Setting up a Lung Cancer Intensity-modulated Radiotherapy Service: A Review of the Reported Clinical Experience
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Citation Excerpt :
Another study has shown that optimised many-field IMRT plans allow dose escalation to the PTV, at a similar level of oesophageal sparing and without unacceptable worsening of dose distribution to the normal lung, in cases of oesophagus overlapping PTV [52]. Another planning study by the same author investigating the dose to the heart, in irradiation of middle and lower lung tumours, showed that the use of non-coplanar fields and IMRT dramatically reduced the dose received by the heart, with the largest benefit seen when the two techniques are combined [53]. A recent study on IMRT for lung cancers looked at the clinical planning trade-offs between OAR sparing and PTV coverage.
Intensity-modulated radiotherapy (IMRT) is being increasingly used for the treatment of non-small cell lung cancer (NSCLC), despite the absence of published randomised controlled trials. Planning studies and retrospective series have shown a decrease in known predictors of lung toxicity (V20 and mean lung dose) and the maximum spinal cord dose. Potential dosimetric advantages, accessibility of technology, a desire to escalate dose or a need to meet normal organ dose constraints are some of the factors recognised as supporting the use of IMRT. However, IMRT may not be appropriate for all patients being treated with radical radiotherapy. Unique problems with using IMRT for NSCLC include organ and tumour motion because of breathing and the potential toxicity from low doses of radiotherapy to larger amounts of lung tissue. Caution should be exercised as there is a paucity of prospective data regarding the efficacy and safety of IMRT in lung cancer when compared with three-dimensional conformal radiotherapy and IMRT data from other cancer sites should not be extrapolated. This review looks at the use of IMRT in NSCLC, addresses the challenges and highlights the potential benefits of using this complex radiotherapy technique.
Intensity-modulated radiation therapy in non-small cell lung cancers
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La radiothérapie conformationnelle avec modulation d’intensité (RCMI) n’est pas une technique validée pour les cancers bronchiques non à petites cellules. Cependant, la proportion de patients irradiés avec modulation d’intensité est croissante. Une revue de la littérature a été réalisée. Les incertitudes physiques et dosimétriques ne sont actuellement pas parfaitement maîtrisées. Des méthodes permettant de prendre en compte ces limitations et de réaliser des contrôles qualité sont en cours de développement. Dans plusieurs études rétrospectives, les survies rapportées après RCMI semblent au moins identiques à celles rapportées après irradiation classique. La RCMI peut être autorisée dans des situations anatomiques spécifiques où la dégradation de la distribution de dose constitue un excès de risque d’échec local. Ce sont les cas des tumeurs de faible mobilité et situées à proximité d’organes critiques tels que la moelle (tumeurs de Pancoast-Tobias, paracardiaques ou paraspinales). La diminution des doses intermédiaires à élevées dans les organes à risque est en faveur de la RCMI mais l’effet des faibles doses dans de larges volumes (poumon, os, tissus non spécifiés le long du trajet des faisceaux) et l’effet de l’augmentation de la dose intégrale sont encore mal connus. En conclusion, des corrélations dose–volume mieux documentées sont indispensables à moyen et long terme. Des études cliniques prospectives sont nécessaires pour évaluer l’impact de la RCMI dans le traitement en routine des cancers bronchiques non à petites cellules en termes d’efficacité et de toxicité notamment respiratoire.
Intensity modulated radiotherapy is increasingly used in non-small-cell lung cancers despite a low level of evidence. A literature review was conducted. Several critical physical and dosimetric uncertainties are however unsolved. Methods to circumvent these limitations are being developed. In several retrospective studies, survival rates were at least similar with intensity-modulated radiotherapy as those reported with three-dimensional irradiation. To date, intensity modulated radiotherapy might be authorized in complex anatomical situations such as tumours close to the spinal cord (such as Pancoast Tobias, paraspinal and paracardiac tumours) or with limited motion amplitudes. Dosimetric benefits should also account for 4D dose distribution issues. The reduction of intermediate and high doses in the organs at risk with intensity modulated radiotherapy is advantageous. However, the effect of low doses in large volumes (lung, bone, unspecified tissues along beam paths) and the effect of increasing integral dose are still poorly known. In conclusion, dose–volume correlations need to be better documented and prospective randomized trials should be encouraged.
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Conference proceedings of the annual meetings of the American Society for Therapeutic Radiology and Oncology (ASTRO) were also searched from the year 2000 to current. Although a systematic review was not carried out to obtain reports on dosimetric studies, specific papers [17–28] were reviewed and summarised to facilitate the discussion (see Appendix 2). The evidence-based series guidelines developed by the CCO PEBC use the methods of the Practice Guidelines Development Cycle [15], as previously described in the prostate cancer guideline [16].
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This functionality allows beams of variable shapes to be administered during a single sequence, possibly proving to be helpful to target tumors that are close to critical tissues. This technique has not been specifically evaluated in thymic tumors, but data obtained in lung cancer are promising to reduce lung and heart toxicity rates.26 In thymic tumors, IMRT may be of great interest in delivering high dose-gradients on pleural recurrences and on lesions abutting the spinal cord.

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Lung radiotherapyPotential benefits of using non coplanar field and intensity modulated radiation therapy to preserve the heart in irradiation of lung tumors in the middle and lower lobes

Abstract

Purpose

Materials and methods

Results

Conclusion

Section snippets

Patient selection

Plans of treatment

PTV coverage

Discussion

Radiother Oncol

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Chest

Lung Cancer

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Int J Radiat Oncol Biol Phys

Fitting of normal tissue tolerance data to an analytic function

Int J Radiat Oncol Biol Phys

NTCP modeling for acute esophagitis in patients treated with conformal radiation therapy for non small cell lung cancer (NSCLC)

Int J Radiat Oncol Biol Phys

Lung radiotherapy
Potential benefits of using non coplanar field and intensity modulated radiation therapy to preserve the heart in irradiation of lung tumors in the middle and lower lobes