Long-term volumetric analysis of vestibular schwannomas following stereotactic radiotherapy: Practical implications for follow-up.

BACKGROUND AND PURPOSE: Transient tumor swelling is a well-known phenomenon following radiotherapy for vestibular schwannomas (VS). We analyzed the long-term volumetric changes of VS after LINAC radiosurgery, in order to determine a time interval during which a true tumor progression can be distinguished from a pseudoprogression. METHODS: Among 63 patients with VS treated by one fraction or fractionated radiotherapy, we selected 52 of them who had a minimal follow-up of 5 years. Maximal axial diameter and three-dimensional tumor volume were measured on each MRI scan. Volume changes were interpreted using different error margins ranging from 10 to 20%. Patients were categorized according to the tumor evolution pattern over time. RESULTS: Median follow-up was 83 months. One tumor (1.9%) remained stable and 26.9% had continuous shrinkage. Applying an error margin of 13%, a transient tumor enlargement was observed in 63.5% of patients, with a first peak at 6-12 months and a late peak at 3-4 years. A true progression was suspected in 4 (7.7%) patients, tumor regrowth starting after the 3rd or 4th year post-treatment. Only one patient required salvage radiotherapy. CONCLUSION: Transient swelling of VS following radiotherapy is generally an early phenomenon but may occur late. In the first 5 years, a true tumor progression cannot be differentiated from a pseudoprogression. A significant tumor expansion observed on 3 sequential MRI scans after the 3rd year may be suggestive of treatment failure. Long-term follow-up is therefore mandatory and no decision of salvage treatment should be made until the 6th year.

Illustration of a fatal radiation-induced lung aneurysm: Is central lung stereotactic radiotherapy to be banned?

Stereotactic body radiation therapy is still controversial for inoperable patients with central lung lesion. We report the case of a 59-year-old woman with previous history of head and neck squamous cell carcinoma who was treated by lung stereotactic body irradiation for an inoperable lymph node in station 10R. One year after, a fibroscopy showed a necrosis of the right main bronchus mucosae and the CT showed a radio-induced aneurysm protruding into the right inferior lobular bronchus. The patient eventually died a few hours later with a massive haemoptysis. This case highlights the potential toxicity of central lung stereotactic body radiation therapy and raises the question of its legitimacy.

Imaging after radiation therapy of thoracic tumors.

Radiation-induced lung disease (RILD) is frequent after therapeutic irradiation of thoracic malignancies. Many technique-, treatment-, tumor- and patient-related factors influence the degree of injury sustained by the lung after irradiation. Based on the time interval after the completion of the treatment RILD presents as early and late features characterized by inflammatory and fibrotic changes, respectively. They are usually confined to the radiation port. Though the typical pattern of RILD is easily recognized after conventional two-dimensional radiation therapy (RT), RILD may present with atypical patterns after more recent types of three- or four-dimensional RT treatment. Three atypical patterns are reported: the modified conventional, the mass-like and the scar-like patterns. Knowledge of the various features and patterns of RILD is important for correct diagnosis and appropriate treatment. RILD should be differentiated from recurrent tumoral disease, infection and radiation-induced tumors. Due to RILD, the follow-up after RT may be difficult as response evaluation criteria in solid tumours (RECIST) criteria may be unreliable to assess tumor control particularly after stereotactic ablation RT (SABR). Long-term follow-up should be based on clinical examination and morphological and/or functional investigations including CT, PET-CT, pulmonary functional tests, MRI and PET-MRI.

Metabolic imaging in non-small-cell lung cancer radiotherapy.

Metabolic imaging by positrons emission tomography (PET) offers new perspectives in the field of non-small-cell lung cancer radiation therapy. First, it can be used to refine the way nodal and primary tumour target volumes are selected and delineated, in better agreement with the underlying tumour reality. In addition, the non-invasive spatiotemporal mapping of the tumour biology and the organs at risk function might be further used to steer radiation dose distribution. Delivering higher dose to low responsive tumour area, in a way that better preserves the normal tissue function, should thus reconcile the tumour radiobiological imperatives (maximising tumour local control) with dose related to the treatment safety (minimising late toxicity). By predicting response early in the course of radiation therapy, PET may also participate to better select patients who are believed to benefit most from treatment intensification. Altogether, these technological advances open avenues to in-depth modify the way the treatment plan is designed and the dose is delivered, in better accordance with the radiobiology of individual solid cancers and normal tissues.

Development of the air righting reflex in cats visually deprived since birth.

Classical experiments on the ability of cats to turn in the air during a free fall, the air righting reflex, have shown that vestibular and visual cues can play a role in this behavior. The development of this air righting reflex in kittens blinded since birth has been studied. The results show that the development in the blinded kittens is the same as in normal kittens with vision: mature by 33 days. This result and the comparison with other studies confirm that the air righting reflex is primarily a vestibular controlled reaction.