Pneumonitis associated with mTOR inhibitors therapy in patients with metastatic renal cell carcinoma: Incidence, radiographic findings and correlation with clinical outcome

Background: Mammalian target of rapamycin (mTOR) inhibitors are approved for use in patients with metastatic renal cell carcinoma (mRCC) and are under investigation in several other malignancies. We assessed the incidence, clinical presentation and computed tomography (CT) findings of pneumonitis associated with mTOR inhibitors in mRCC. Correlation between radiological findings of pneumonitis and clinical outcome was also determined. Methods: We retrospectively reviewed the clinical data and serial CT scans from patients with mRCC treated with either temsirolimus or everolimus. Serial chest CT scans were reviewed in consensus, read by two independent radiologists for the presence of pneumonitis, and corresponding clinical data were reviewed for symptoms and clinical outcome. The baseline and follow up CTs were reviewed to assess outcome to therapy. Results: The study population consisted of 46 pts, 21 treated with temsirolimus and 25 with everolimus (M:F 2.5:1; median 63 years, range 31-79 years). CT evidence of pneumonitis was seen in 14/46 pts (30%), at a median of 56 days on mTOR inhibitor treatment (range 31-214 days). Respiratory symptoms at the time of radiographically detected pneumonitis, were observed in 7 pts. Stable disease (SD) by Response Evaluation Criteria in Solid Tumours (RECIST) was achieved in 12/14 pts (86%) who developed radiographic pneumonitis compared to 14/32 (44%) without pneumonitis (p = 0.01) The mean change of tumour long axis size for target lesions by RECIST, normalised for 30 days on therapy was -2.9% in the pneumonitis group and +4.3% in the non-pneumonitis group (p =.002). Conclusions: Preliminary data suggest that pneumonitis may be a marker of stable disease by RECIST and therefore, of therapeutic benefit. Careful patient assessment should be undertaken before the drug is discontinued.