Potential role of mTOR phosphorylation status as a negative predictor to everolimus plus octreotide in NETs

• Published in: Journal of clinical oncology Vol. 32; no. 3_suppl; p. 484
• Main Authors: Casanovas, Oriol, Capdevila, Jaume, Barriuso, Jorge, Teule, Alex, Castellano, Daniel E., Manzano, Jose Luis, Lopez, Carlos, Alonso, Vicente, Garcia Carbonero, Rocio, Dotor, Emma, Martinez, Alba, Salazar, Ramon
• Format: Journal Article
• Language: English
• Published: 20-01-2014
• ISSN: 0732-183X; 1527-7755
• DOI: 10.1200/jco.2014.32.3_suppl.484

Abstract only 484 Background: Everolimus treatment is currently approved for a few tumor types and currently evaluated in several other malignancies, including NETs. Nevertheless, there is an urgent need for histological or molecular factors of prediction of response, as these would help discriminate subgroups of patients more likely to respond. Here we report on a biological sub-study on histological markers to unravel the relationship between the activation of the IGFR-mTOR-S6 signal transduction pathway with treatment response to everolimus plus octreotide combined therapy in patients with GI NETs. Methods: IGFR-1 (Abcam #54274), phospho-mTOR (Ser-2448, Cell Signaling #2976) and phospho-S6 (Ser-235/236, Cell Signaling #4857) were evaluated by immunohistochemistry (according to Choe G. et al, Cancer Research. 2003) from paraffin embedded blocks from patients with progressive locally advanced or metastatic non-functioning GI NETs, included in a national phase II clinical trial (EVERLAR, NCT01567488). Study endpoint was PFS, and 50% of the patients had progressed at the time of analysis. Univariant (Chi square) and multi-variant (COX) statistical analysis were performed. Results: 38 patients were evaluated with a median age of 62.7 years, balanced on gender (57 % vs. 42%), of which 76.3% were metastatic, mostly to liver. IGF1R positivity showed a nonsignificant trend to association to treatment response (50% progression vs. 21% progression, p=0.15). Nevertheless, mTOR activation (phospho-mTOR positivity) was associated with progression (median PFS of 100 days vs. 225 days, p=0.019). Multivariant COX regression analysis showed a Hazard Ratio of 2.96 [0.8-10.2] (p=0.087) for phospho-mTOR activation. Conclusions: Contrarily to expected results, mTOR activation status determined by phospho-mTOR immunohistological positivity seems to be associated to worse outcome in terms of progression to everolimus+somatostatin analogs in GI NETs patients. This could be indicative of a refractoriness or primary resistance to treatment based on a threshold of mTOR activation, possibly due to activation feedback-loops.