Timing of brain metastases development in metastatic renal cell cancer patients treated with targeted therapies and survival outcomes: An Australian multicenter study

AIM: Targeted therapy (TT) has improved survival for metastatic renal cell carcinoma (mRCC). However, survival is usually limited if brain metastases (BMs) develop. We aimed to evaluate survival outcomes in mRCC patients based on timing of BM diagnosis. METHODS: We conducted a multicenter, retrospective study of mRCC patients with BM who received TT at any point between 2005 and 2014. We determined overall survival (OS) from stage IV diagnosis, TT initiation and BM diagnosis, and prognostic factors. Patients were grouped into three categories: synchronous-BM, metachronous-BM diagnosed while conservatively managed (metachronous-BM before TT) and metachronous-BM diagnosed during TT. Survival was calculated by Kaplan-Meier method and predictors were calculated using Cox hazards regression. RESULTS: Incidence of BM was 17% in mRCC patients treated with TT (two centers). Fifty-four mRCC-BM patients were identified from five tertiary centers. Twenty-eight percentage (15/54) had synchronous-BM, 28% (15/54) had metachranous-BM before TT and 44% (24/54) had metachronous-BM during TT. Most had central nervous system (CNS) symptoms at BM diagnosis (78%; 42/54). Median OS from stage IV diagnosis, TT commencement and BM diagnosis was 28 months (95% confidence interval [CI] 16-43), 19 months (95% CI 9-26) and 9 months (95% CI 5-16), respectively. Synchronous-BM group trended toward poorer survival from TT commencement (P = 0.06). Metachronous-BM during TT group had lower survival from BM diagnosis than synchronous-BM and metachronous-BM before TT group (P < 0.001). Eight of 50 deaths (16%) were from neurological complications. The presence of CNS symptoms did not predict worse survival from stage IV diagnosis (P = 0.73). CONCLUSION: In patients with mRCC, the development of BM while on TT portends shorter prognosis compared with synchronous diagnosis of BM at stage IV disease or metachronous BM developed prior to commencing TT. The presence of CNS symptoms does not predict worse survival

Dual targeting of FGFR3 and ERBB3 enhances the efficacy of FGFR inhibitors in FGFR3 fusion-driven bladder cancer

BACKGROUND: Mutations and fusions in Fibroblast Growth Factor Receptor 3 (FGFR3) occur in 10-20% of metastatic urothelial carcinomas and confer sensitivity to FGFR inhibitors. However, responses to these agents are often short-lived due to the development of acquired resistance. The objective of this study was to identify mechanisms of resistance to FGFR inhibitors in two previously uncharacterised bladder cancer cell lines harbouring FGFR3 fusions and assess rational combination therapies to enhance sensitivity to these agents. METHODS: Acquired resistance to FGFR inhibitors was generated in two FGFR3 fusion harbouring cell lines, SW780 (FGFR3-BAIAP2L1 fusion) and RT4 (FGFR3-TACC3 fusion), by long-term exposure to the FGFR inhibitor BGJ398. Changes in levels of receptor tyrosine kinases were assessed by phospho-RTK arrays and immunoblotting. Changes in cell viability and proliferation were assessed by the Cell-Titre Glo assay and by propidium iodide staining and FACS analysis. RESULTS: Long term treatment of FGFR3-fusion harbouring SW780 and RT4 bladder cancer cell lines with the FGFR inhibitor BGJ398 resulted in the establishment of resistant clones. These clones were cross-resistant to the clinically approved FGFR inhibitor erdafitinib and the covalently binding irreversible FGFR inhibitor TAS-120, but remained sensitive to the MEK inhibitor trametinib, indicating resistance is mediated by alternate activation of MAPK signalling. The FGFR inhibitor-resistant SW780 and RT4 lines displayed increased expression of pERBB3, and strikingly, combination treatment with an FGFR inhibitor and the ATP-competitive pan-ERBB inhibitor AZD8931 overcame this resistance. Notably, rapid induction of pERBB3 and reactivation of pERK also occurred in parental FGFR3 fusion-driven lines within 24 h of FGFR inhibitor treatment, and combination treatment with an FGFR inhibitor and AZD8931 delayed the reactivation of pERBB3 and pERK and synergistically inhibited cell proliferation. CONCLUSIONS: We demonstrate that increased expression of pERBB3 is a key mechanism of adaptive resistance to FGFR inhibitors in FGFR3-fusion driven bladder cancers, and that this also occurs rapidly following FGFR inhibitor treatment. Our findings demonstrate that resistance can be overcome by combination treatment with a pan-ERBB inhibitor and suggest that upfront combination treatment with FGFR and pan-ERBB inhibitors warrants further investigation for FGFR3-fusion harbouring bladder cancers

K-Ras mutation and amplification status is predictive of resistance and high basal pAKT is predictive of sensitivity to everolimus in biliary tract cancer cell lines

Advanced biliary tract cancer (BTC) has a poor prognosis and limited treatment options. The PI3K/Akt/mTOR signalling pathway is hyperactivated in a subset of BTCs, and clinical activity of the mTOR inhibitor everolimus has been observed in some patients with BTC. The goal of this study was to identify biomarkers predictive of everolimus response. Twenty BTC cell lines were assessed for everolimus sensitivity with a spectrum of growth inhibitory responses observed. Molecular biomarkers of sensitivity and resistance were identified by interrogation of the activation status of the Ras/MAPK and PI3K/Akt/mTOR pathways. K-Ras mutations and/or amplifications were identified in 45% of cell lines and were associated with resistance to everolimus. Activating mutations in PIK3CA or loss of PTEN was not predictive of everolimus response; however, high basal levels of pAKT were associated with sensitivity, independent of Ras/MAPK pathway activation status. Notably, everolimus inhibited mTOR signalling to a similar extent in sensitive and resistant cell lines, suggesting that relative dependence on the mTOR pathway rather than the magnitude of pathway inhibition determines everolimus response. Consistent with the known limitations of rapalogs, everolimus induced feedback-mediated activation of AKT in BTC cell lines, which could be overcome by cotreatment with an AKT inhibitor or ATP-competitive mTORC1/mTORC2 inhibitors. However, both approaches failed to induce greater apoptosis compared to everolimus, and mTORC1/mTORC2 kinase inhibitors induced compensatory activation of pERK, identifying an inherent limitation of these agents in BTC cell lines. These findings suggest that future trials of everolimus in BTC would benefit from preselecting patients based on their K-Ras and PI3K/mTOR pathway activation status. The study also identifies strategies for enhancing inhibition of the PI3K/mTOR pathway in BTC cell lines

Risk of febrile neutropenia and early treatment cessation in men receiving standard and dose-reduced 3-weekly docetaxel for metastatic castration-resistant prostate cancer

BACKGROUND: Docetaxel is an effective therapy for metastatic castration-resistant prostate cancer (mCRPC); however, many patients experience febrile neutropenia (FN) and cease treatment early due to toxicity. It is not known whether lower dose (LD) q3-weekly docetaxel impacts toxicity or efficacy. METHODS: Multicenter retrospective study included 166 patients with mCRPC who received q3-weekly docetaxel between 2010 and 2015. Demographic, disease, chemotherapy (standard dose, SD > 60 mg/m2 vs LD ≤ 60 mg/m2 ) and toxicity data were collected. Univariable and multivariable logistic and competing risk regression models evaluated docetaxel-dose association with FN and early treatment cessation (ETC) due to toxicity. Associations between dose and efficacy end points were also evaluated. Analyses were repeated employing inverse propensity score weights. RESULTS: Patients who received LD docetaxel (28.9%) were older with poorer Eastern Cooperative Oncology Group (ECOG) status. Fifteen percent of patients experienced FN, with a nonsignificant trend to lower incidence in the LD group (multiple adjusted odds ratio [OR] = 0.42; P = 0.21). Neither baseline patient nor prior treatment factors were predictive of FN. ETC due to toxicity occurred in 35%, with risk associated with increasing age, comorbidity count and poorer ECOG. There was no difference between LD and SD with respect to ETC due to toxicity, in unweighted and weighted analyses (LD vs SD, multivariable weighted hazard ratio [HR] = 1.47; P = 0.08). LD was associated with reduced prostate-specific antigen (PSA) response (50% vs 66.1%, multivariable weighted HR = 0.54; P = 0.03) and overall survival (median 7.9 vs 13.8 months, multivariable weighted HR = 2.19; P < 0.0001). CONCLUSIONS: LD docetaxel for mCRPC did not mitigate the risk of FN or ETC due to toxicity. Dose reduction may result in poorer PSA response and survival