Study of Pulmonary MRI for the Diagnosis of Bronchiolitis Obliterans Syndrome After Allogeneic Stem Cell Transplantation

Bronchiolitis Obliterans Syndrome (BOS) is a major complication of Hematopoietic Stem cell Transplantation (HSCT) occurring in the context of chronic GVHD and associated with a poor prognosis. The diagnosis of BOS is based on functional (Pulmonary Functional Tests) and morphological criteria (chest CT-scan). Early diagnosis of BOS represents an unmet need and would facilitate early therapeutic interventions. Lung MRI has been recently developed with new sequences facilitating morphological and functional lung analysis in various inflammatory contexts. The goal of this study is to compare the morphological performances of chest CT-scan and MRI

Patients undergoing allogeneic stem cell transplantation may develop non-infectious respiratory complication related to chronic graft versus host disease and called bronchiolitis obliterans syndrome (BOS). The occurrence of BOS is associated with a decreased survival reaching 13% at 5 years (Dudek et al, BBMT 2003). Thus, screening and diagnosis of BOS appear as a priority of post-transplant patients monitoring, in order to begin early therapy if needed. To this end, patients undergo systematic and regular screening using pulmonary function tests (PFTs). In case of abnormal PFTs, tests are completed the screening of respiratory infections and chest computed tomographic scan (CT-scan) is performed. A report from the National Institute of Health described the following criteria required for the diagnosis of BOS : FEV1/vital capacity \< 0.7, FEV1 \< 75% or a decline \>/= 10% from baseline, residual volume \> 120%, absence of documented infection, and the presence of CT-scan signs suggestive of BOS : air trapping by expiratory CT or small airway thickening or bronchiectasis.

BOS severity depends on the development of fibrotic and fixed damages, poorly responding to therapies. New tools are needed in order to favor early BOS diagnosis.

A recent study from our center showed that repeated CT-scans in stem cell transplant patients is associated with increased risk of neoplasia. In addition, recent studies from our center evaluated the use of pulmonary MRI providing good performance without X-ray exposure (Dournes G et al, Radiology 2015 et Dournes G et al, Eur Radiol 2015).

More recently, Renne et al (Radiology 2015) studied the performance of pulmonary MRI coupled with oxygen transfer analysis for the diagnosis of chronic lung allograft dysfunction. This study showed altered imaging parameters in patients developing BOS, including patients with early BOS stage (0p stage).

As pathogenic mechanisms seem to be shared between post-stem cell transplant and post-lung transplant BOS, we hypothesize that pulmonary MRI with oxygen transfer analysis and ultra short echo time may represent a non-invasive, non-irradiating and sensitive research tool for the detection and quantification of pulmonary lesions in patients screened for post-stem cell transplant BOS.

Thus, 20 patients who underwent allogeneic stem cell transplantation and show abnormal respiratory function over a 2 year period study are expected. They will be included according to the following criteria : age \> 18 yo, \> 3 months post-transplant, absence of documented pulmonary infection, or with a minimum of 6 weeks after a documented pulmonary infection, and the following BOS criteria : abnormal PFTs (FEV1/VC \< 0.7, FEV1 \< 0.75, residual volume \< 120% of expected value) and/or chest CT-scan showing air trapping or small airway thickening. Similarly to lung transplant criteria, stage 0p BOS defined according to FEF25-75 values (Estenne et al, JHLT 2002), for which pulmonary MRI with oxygen transfer may guide to early BOS diagnosis, will be added.

Patients who give their consent will perform a pulmonary MRI, in the absence of contraindication, using different sequences to evaluate morphologic and functional performances of pulmonary MRI. We will compare CT-scan and MRI performances using blinded analysis from two radiologists.

Eligibility Criteria:
Inclusion Criteria:

* Patient ≥ 18 yo ;
* Patient who underwent an allogeneic stem cell transplantation (SCT)
* \> 3 months post-SCT
* With evidence of

  * respiratory symptoms, and/or
  * Pathological PFTs defined by : obstructive syndrome (FEV1 :vital capacity/CVF \< 0.7), FEV1 \< 0.75 of pre-SCT values, residual volume \> 120%, and/or ;
  * Altered PFTs consistent with 0p stage described in lung transplantation BOS: FEV1 decline ≥ 10 % and/or FEF25-75 decline ≥ 25% compared to pre-SCT PFTs, and/or ;
  * Abnormal chest CT-scan with findings consistent with BOS: evidence of air trapping on expiratory CT-scan, bronchiectasis, and/or airway thickening.

Exclusion Criteria:

* Contraindication for MRI ;
* Contraindication of oxygen administration ;
* Decompensation of altered respiratory function ;
* Acute respiratory infection (bacterial, fungal or viral) documented in the last 6 weeks ;