[Upper aerodigestive tract cancers: clinical benefits of conformal radiotherapy and intensity modulation]

[IMRT and head and neck tumors: does differential fractionation have a role?]

For head and neck cancer, intensity-modulated radiation therapy (IMRT) provides benefits in terms of coverage of the target tumour volume and reduction of the dose to organs at risk. Altered fractionation called SMART (simultaneous modulated accelerated radiation therapy) or SIB (simultaneous integrated boost), equivalent to the "concomitant boost" of conventional techniques, provides additional theoretical gain in the therapeutic index and simplifies the practical implementation of the treatment. The impact on tumour control and acute and late toxicities is encouraging but needs to be confirmed by prospective clinical studies with sufficient follow-up. A lot of different protocols have been tested without really bringing out a "gold standard". However, the current results tend to suggest a SIB/SMART-IMRT moderately accelerated without combined chemotherapy for limited stages (I and II), and SIB-IMRT slightly accelerated with induction and/or concomitant chemotherapy for more advanced stages (III and IV).

[Cancers of the nasal cavity and paranasal sinuses: clinicopathological, etiological and therapeutic aspects]

Sinonasal cancers are rare and are often associated with occupational exposure that should be researched. Their diagnosis is often delayed. Carcinomas are the most common histological variety. The aim of the present report is to review the main scientific literature about sinonasal cancer to identify their clinicopathological features, and their main causes and treatment modalities. The treatment of these tumors is surgical, usually followed by radiotherapy.

Conservation of salivary function and new external head and neck radiation techniques

INTRODUCTION

New radiation therapy techniques seek to adapt dose distribution to three-dimensional tumor geometry, so as to deliver the lowest possible dose to normal tissue and at-risk organs. This is expected to enhance locoregional control and survival and to reduce complications and thereby improve quality of life. Post-radiation xerostomia significantly deteriorates quality of life.

MATERIAL AND METHODS

New external radiation techniques (such as intensity-modulated conformal radiation therapy, RapidArc VMAT arc therapy, tomotherapy, CyberKnife(®), protontherapy, use of carbon ions) applicable in ENT are reviewed.

RESULTS

Preliminary data show interesting results in terms of salivary function with highly conformal techniques.

CONCLUSION

In France, assessment is ongoing, financed under the Health Ministry's "Support for Expensive Innovatory Techniques" scheme (STIC [Soutien aux techniques innovantes coûteuses]), as routine use is growing rapidly.

A treatment planning comparison of combined photon-proton beams versus proton beams-only for the treatment of skull base tumors

PURPOSE

To compare treatment planning between combined photon-proton planning (CP) and proton planning (PP) for skull base tumors, so as to assess the potential limitations of CP for these tumors.

METHODS AND MATERIALS

Plans for 10 patients were computed for both CP and PP. Prescribed dose was 67 cobalt Gray equivalent (CGE) for PP; 45 Gy (photons) and 22 CGE (protons) for CP. Dose-volume histograms (DVHs) were calculated for gross target volume (GTV), clinical target volume (CTV), normal tissues (NT), and organs at risk (OARs) for each plan. Results were analyzed using DVH parameters, inhomogeneity coefficient (IC), and conformity index (CI).

RESULTS

Mean doses delivered to the GTVs and CTVs with CP (65.0 and 61.7 CGE) and PP (65.3 and 62.2 Gy CGE) were not significantly different (p > 0.1 and p = 0.72). However, the dose inhomogeneity was drastically increased with CP, with a mean significant incremental IC value of 10.5% and CP of 6.8%, for both the GTV (p = 0.01) and CTV (p = 0.04), respectively. The CI(80%) values for the GTV and CTV were significantly higher with PP compared with CP. Compared with CP, the use of protons only led to a significant reduction of NT and OAR irradiation, in the intermediate-to-low dose (< or =80% isodose line) range.

CONCLUSIONS

These results suggest that the use of CP results in levels of target dose conformation similar to those with PP. Use of PP significantly reduced the tumor dose inhomogeneity and the delivered intermediate-to-low dose to NT and OARs, leading us to conclude that this treatment is mainly appropriate for tumors in children.

Conformity index: a review

We present a critical analysis of the conformity indices described in the literature and an evaluation of their field of application. Three-dimensional conformal radiotherapy, with or without intensity modulation, is based on medical imaging techniques, three-dimensional dosimetry software, compression accessories, and verification procedures. It consists of delineating target volumes and critical healthy tissues to select the best combination of beams. This approach allows better adaptation of the isodose to the tumor volume, while limiting irradiation of healthy tissues. Tools must be developed to evaluate the quality of proposed treatment plans. Dosimetry software provides the dose distribution in each CT section and dose-volume histograms without really indicating the degree of conformity. The conformity index is a complementary tool that attributes a score to a treatment plan or that can compare several treatment plans for the same patient. The future of conformal index in everyday practice therefore remains unclear.

Proposition de sélection et délimitation des volumes cibles microscopiques péritumoraux dans les cancers de la cavité buccale et de l'oropharynx (aires ganglionnaires exclues)

This article reviews the concept of selectivity in peritumoral microscopic disease to be included in the Clinical Target Volume (CTV) for elective treatment for oral cavity and oropharyngeal squamous cell carcinoma, using the local tumoral spread. The objective of the present article is to present a procedure for the delineation of the target volumes, required for an appropriate application of 3-DCRT and IMRT for head and neck cancers. These propositions are for the delineation of microscopic peritumoral target volumes when external beam irradiation is required. CTVs are illustrated on CT sections.

Recommandations pour un protocole d’assurance de qualité de la radiothérapie conformationnelle avec modulation d’intensité des cancers de la tête et du cou

Head and neck tumors represent very interesting targets for IMRT techniques because of the complex shape of the structures and the organs at risk close by. The use of this kind of techniques requires a quality assurance protocol. The physicists of the GORTEC group shared their experience to define some recommendations in order to draw up a QA protocol. The dosimetric verification of the treatment plans (in terms of absolute and relative dose), the control of the reproducibility of the patient positioning and the use of a record and verify system to control the different parameters form the main parts of these recommendations. Each chapter comprises a description of the different methods, recommendations concerning the equipment, the adopted tolerances, the frequency of controls. At the end of each chapter, a table summarizes the main actions to carry out. These recommendations will allow to harmonize our practices whatever the softwares and the accelerator that are being used. They will simplify the task of the teams that wish to implement IMRT for head and neck tumors.

Radiothérapie conformationnelle avec modulation d'intensité des cancers des voies aérodigestives supérieures avec irradiation bilatérale du cou : résultats préliminaires

PURPOSE

To report preliminary results of a prospective study of intensity-modulated radiotherapy (IMRT) for head and neck squamous cell carcinoma (HNC) with bilateral irradiation of the neck.

PATIENTS AND METHODS

At the Alexis Vautrin Cancer Center, 23 patients have been treated with IMRT for HNC since January 2002-August 2003. The first 10 patients with a minimum follow-up of 3 months were analyzed. All tumors were oropharyngeal. There were four females and six males, with a mean age of 50 years (range 39-66). Stages were I-II in eight and III-IV in two. CTV1 was microscopic disease and N0 neck (prescribed dose : 50 Gy) and CTV2 was macroscopic disease and the volume at risk (prescribed dose: 66-70 Gy). PTV were CTV + 5 mm. Patient's immobilization consisted of a five-point head neck shoulder thermoplastic mask. Set-up verifications were done by semi-automatically matching portal images and digitized reconstructed radiographs. IMRT used dynamic multileaf collimation. Five patients (group A) received 50 Gy IMRT (two post-operative and three with a brachytherapy boost with a mean dose: 27.5 Gy), and five patients (group B) received 66-70 Gy IMRT (four post-operative). Acute and late normal tissue effects were graded according to the RTOG-EORTC radiation morbidity scoring criteria.

RESULTS

With a median follow-up of 7.4 months (range 3-18.5), no patient died or had loco-regional relapse. The displacements were <4 mm in 98% cases. CTV1 and 2 received 95% of the prescribed dose in 100% of the volume. On average the mean dose to the contralateral parotid was 25.5 Gy for group A vs. 31 Gy for group B (P = 0.09). Mean doses <26 Gy were obtained in three of five patients in group A vs. zero of five patients in group B (P = 0.04). Acute skin toxicities were grade 1 in five patients, grade 2 in four and grade 3 in one. Acute mucositis cases were grade 1 in three patients, grade 2 in five and localized grade 3 in two. At 3 months, 50% of the patients had a grade 0-1 late xerostomia.

CONCLUSION

The 26 Gy dose limit constraint to the contralateral parotid was easier to satisfy when IMRT was prescribed at a maximum dose of 50 Gy. Acute toxicity is low. The displacements in the mask indicate that it is possible to define the PTV as CTV + 4 mm. This reduction should decrease the mean dose to the parotids. At 3 months, a 50% rate of grade 0-1 late xerostomia encourages the hope of a very low rate at 2 years.

[Conformal index and radiotherapy]

Goal of radiotherapy is to treat patient with the best therapeutic ratio, i.e. the highest local control and the lowest toxicity rates. The conformal approach, three-dimensional conformal radiotherapy or intensity-modulated radiotherapy, is based on imageries, up-dated 3-D treatment planning systems, immobilization systems, restricted quality assurance and treatment verification. The aim is to ensure a high dose distribution tailored to the limits of the target volume, while reducing exposure of normal tissues. The evaluation tools used for optimizing treatment are the visual inspection of the dose distribution in various planes, and the dose-volume histograms, but they do not fully quantify the conformity of dose distributions. The conformal index is a tool for scoring a given plan or for evaluating different treatment plans for the same patient. This paper describes the onset and evolution of conformal index and his potential application field.