A recent study published online in BioMed Central Cancer shows how the presence and onset rate of side effects to treatment with mTOR inhibitors, such as everolimus, is associated with tumour response and progression free survival.

From 2007 to 2011, metabolic toxicities were collected retrospectively from patients treated with an mTOR inhibitor (everolimus, temsirolimus) for metastatic renal cell carcinoma (mRCC). Patients had received treatment with an mTOR inhibitor for at least 28 days. Changes in various blood parameters were analysed and efficacy was assessed by progression-free survival (PFS) and tumour response. Data were collected from seventy-five patients (everolimus = 44 patients; temsirolimus = 31 patients).

Metabolic toxicities, such as hyperglycemia, hypophosphatemia and increase in liver transaminases (enzymes) were significantly correlated with the efficacy of mTOR inhibitors, while lymphopenia was correlated with a lack of efficacy. On the other hand, hypercholesterolemia and hypertriglyceridemia had no relationship with efficacy of mTOR inhibitors. In addition, the onset time of severe toxicity was short and occurred before the first tumour assessment.

Metabolic toxicities, such as hyperglycemia, hypophosphatemia and lymphopenia were significantly associated with tumour response and/or progression free survival and should be monitored as predictors of response to mTOR inhibitors.

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