Phase II study of temsirolimus in women with recurrent or metastatic endometrial cancer: a trial of the NCIC Clinical Trials Group

Abstract

Purpose: Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene, and loss of function mutations are common and appear to be important in the pathogenesis of endometrial carcinomas. Loss of PTEN causes deregulated phosphatidylinositol-3 kinase/serine-threonine kinase/mammalian target of rapamycin (PI3K/Akt/mTOR) signaling which may provide neoplastic cells with a selective survival advantage by enhancing angiogenesis, protein translation, and cell cycle progression. Temsirolimus, an ester derivative of rapamycin that inhibits mTOR, was evaluated in this setting.

Patients and methods: Sequential phase II studies evaluated single-agent activity of temsirolimus in women with recurrent or metastatic chemotherapy-naive or chemotherapy-treated endometrial cancer. Temsirolimus 25 mg intravenously was administered weekly in 4-week cycles.

Results: In the chemotherapy-naive group, 33 patients received a median of four cycles (range, one to 23 cycles). Of the 29 patients evaluable for response, four (14%) had an independently confirmed partial response and 20 (69%) had stable disease as best response, with a median duration of 5.1 months (range, 3.7 to 18.4 months) and 9.7 months (range, 2.1 to 14.6 months). Only five patients (18%) had progressive disease. In the chemotherapy-treated group, 27 patients received a median of three cycles (range, one to six cycles). Of the 25 patients evaluable for response, one (4%) had an independently confirmed partial response, and 12 patients (48%) had stable disease, with a median duration of 4.3 months (range, 3.6 to 4.9 months) and 3.7 months (range, 2.4 to 23.2 months). PTEN loss (immunohistochemistry and mutational analysis) and molecular markers of PI3K/Akt/mTOR pathway did not correlate with the clinical outcome.

Conclusion: mTOR inhibition with temsirolimus has encouraging single-agent activity in endometrial cancer which is higher in chemotherapy-naive patients than in chemotherapy-treated patients and is independent of PTEN status. The difference in activity according to prior therapy should be factored into future clinical trial designs.

Fig 1.

Representation of PTEN/Akt/mTOR (phosphatase and tensin homolog/Akt/mammalian target of rapamycin) pathway. CCI-779, temsirolimus; EIF-4E, eukaryotic translation initiation factor 4E; P13K, phosphatidylinositol 3-kinase; P70s6k, phosphorylated s6 kinase; Rad 001, everolimus; RTK, receptor tyrosine kinase.

Fig 2.

Waterfall plots demonstrating best radiologic response for (A) Group A (IND160A) and (B) Group B (IND160B) of the NCIC Clinical Trials Group and (C) duration of therapy for Group A and Group B.