Cabozantinib (C) in combination with atezolizumab (A) in urothelial carcinoma (UC): Results from Cohorts 3, 4, 5 of the COSMIC-021 study

4504

Background: C, a multitargeted receptor tyrosine kinase inhibitor (TKI), promotes an immune-permissive environment that may enhance response to immune checkpoint inhibitors (ICIs). COSMIC-021, a multicenter phase 1b study, is evaluating C + A (anti‒PD-L1 therapy) in various solid tumors (NCT03170960). C + A demonstrated encouraging clinical activity in cohort 2 of COSMIC-021 in patients (pts) with UC previously treated with platinum-containing chemotherapy (chemo) (Pal S et al. ASCO 2020. Abstract 5013). Outcomes of C + A from 3 other UC cohorts (C3, C4, C5) are presented. Methods: Pts with inoperable locally advanced/metastatic UC with transitional cell histology and ECOG PS 0‒1 were eligible. Pts enrolled in C3 and C4 had no prior therapy and were cisplatin-based chemo ineligible (C3) or eligible (C4). C5 enrolled pts with one prior ICI and no prior VEGFR-TKI therapy. Pts received C 40 mg PO QD and A 1200 mg IV Q3W. CT/MRI scans were performed Q6W for first year and Q12W thereafter. The primary endpoint is objective response rate (ORR) per RECIST v1.1 by investigator. Other endpoints: safety, duration of response (DOR), PFS, and OS. Results: Thirty pts each were enrolled in C3 and C4, and 31 in C5. Baseline characteristics for C3, C4, and C5, respectively: median age, 74 y, 66 y, 68 y; male, 67%, 73%, 55%; ECOG PS 1, 63%, 57%, 74%; lung/liver metastasis; 33%/17%, 40%/20%, 58%/23%; ≥3 tumor sites, 30%, 43%, 45%; bladder as primary site, 67%, 70%, 71%. As of Nov 30, 2021, the median follow-up for C3, C4, and C5 was 27.9, 19.1, and 32.9 mo, respectively, with 1, 6, and 1 pts on treatment. C + A demonstrated clinical benefit across all cohorts (Table). Most common treatment-related adverse events (TRAEs) of any grade across C3, C4, and C5, respectively, were diarrhea (43%, 33%, 35%), nausea (27%, 17%, 26%), fatigue (27%, 27%, 48%), and decreased appetite (33%, 27%, 39%); grade 3/4 TRAEs occurred in 63%, 43%, and 45%, and there was no grade 5 TRAE. Conclusions: C + A demonstrated encouraging clinical activity with manageable toxicity in inoperable locally advanced/metastatic UC as first-line systemic therapy in cisplatin-based chemo eligible/ineligible pts and as second- or later line in pts who received prior ICI. Clinical trial information: NCT03170960. [Table: see text]

Predictive and prognostic biomarker identification in a large cohort of androgen receptor-positive salivary duct carcinoma patients scheduled for combined androgen blockade

6071

Background: Patients suffering from recurrent or metastatic (R/M) salivary duct carcinoma (SDC) are often treated with combined androgen blockade (CAB). This treatment however frequently fails (response rates: 18-53%), resulting in a worse prognosis. Therefore, biomarkers that have prognostic value and can predict treatment response are urgently needed. Methods: mRNA from 77 R/M androgen receptor (AR) positive SDC patients treated with leuprorelin acetate combined with bicalutamide was extracted from pre-treatment tumor specimens. AR, Notch, Mitogen-Activated Protein Kinase (MAPK), Transforming Growth Factor beta (TGFβ), Estrogen Receptor (ER), Hedgehog (HH) and the Phosphoinositide 3-Kinase (PI3K) signaling pathway activities were calculated based on expression levels of relevant target genes. Besides this, 5-alpha reductase type 1 ( SRD5A1) expression and Human Epidermal growth factor Receptor 2 (HER2) status were determined. Clinical benefit was defined as complete or partial response or stable disease ≥6 months. Results: Of the 7 signaling pathways, AR pathway activity was the best predictor of clinical benefit (AUC 0.67, 95%-CI 0.54-0.80). At a threshold of 47.8, 21% of the patients tested negative, with a negative predictive value of 93%. SRD5A1 expression outperformed the signaling pathways regarding predictive value (AUC 0.78, 95%-CI 0.67-0.88). Fitting of a multivariable model led to the identification of SRD5A1, Notch and TGFβ as most predictive combination (AUC 0.82, 95%-CI 0.72-0.91). AR, Notch, HH and SRD5A1 were also of prognostic importance regarding progression free survival and SRD5A1 expression levels also for overall survival (median of 175.0 weeks for high versus 96.7 weeks for low expression). Conclusions: Our study revealed predictive and/or prognostic value of AR, HH, Notch and TGFβ signaling activities and SRD5A1 expression in SDC patients treated with CAB. AR pathway activity can be used for identifying non-responders. Further clinical validation is required before implementation of these biomarkers in clinical practice. The observed role of SRD5A1 expression in CAB response forms a rational basis for including SRD5A1-inhibitors in the treatment of SDC patients.[Table: see text]

Update and external validation of a multivariable prediction model for tube feeding dependency for at least four weeks during chemoradiotherapy for head and neck cancer

6040

Background: Patients who receive chemoradiation or bioradiation (CRT/BRT) for locally advanced head and neck squamous cell carcinoma (LAHNSCC) often experience high toxicity rates, which may interfere with oral intake, leading to (temporary) tube feeding (TF) dependency. International guidelines recommend gastrostomy insertion when the expected use of TF exceeds four weeks. In this study we aimed to update and externally validate a prediction model to identify patients in need for TF for at least four weeks, meeting the international criteria for prophylactic gastrostomy insertion. Methods: This retrospective multicenter cohort study was performed in four tertiary referral head and neck cancer centers in the Netherlands. The prediction model was developed using data from the University Medical Center Utrecht and the Netherlands Cancer Institute. The model was externally validated in patients from the Maastricht University Medical Center and Radboud University Medical Center. The primary endpoint was TF, initiated during or within 30 days after completion of CRT/BRT, and administered for at least four weeks. Potential predictors were retrieved from patient medical records and radiotherapy dose-volume parameters were calculated. Results: The developmental and validation cohort included 409 and 334 patients respectively. Multivariable analysis showed significant predictive value (p < 0.05) for adjusted diet at start of CRT/BRT, percentage weight change prior to treatment initiation, WHO performance status, tumor-site, nodal stage, mean radiation dose to the contralateral parotid gland, and mean radiation dose to the oral cavity. The area under the receiver operating characteristics curve for the updated model was 0.73 and after external validation 0.64. Positive and negative predictive value at 90% cut off were 80.0% and 48.2% respectively. Conclusions: This externally validated prediction model to estimate TF-dependency for at least four weeks in LAHNSCC patients performs well. This model, which will be presented, can be used in clinical practice to guide personalized decision making on prophylactic gastrostomy insertion.

Phase I study of afatinib plus selumetinib in patients with KRAS mutation-positive colorectal, non-small cell lung and pancreatic cancer

3613

Background: Mutations in the KRAS gene result in a constitutively activated RAS-RAF-MEK-ERK (MAPK) pathway. In KRAS mutant tumors, the anti-tumor activity of MEK inhibitors is limited due to intrinsic resistance caused by feedback activation of upstream epidermal growth factor receptors (HER). This upstream activation not only reactivates MAPK, but also the phosphoinositide 3-kinase (PI3K)-AKT pathway in preclinical research. Based on these data, a phase I clinical trial was initiated with the combination of the orally administered pan-HER inhibitor afatinib and the MEK inhibitor selumetinib in patients with KRAS mutant and PIK3CA wildtype colorectal cancer (CRC), non-small cell lung cancer (NSCLC), or pancreatic cancer to determine the recommended phase 2 regimen (RP2R). Methods: In this multicentre study, patients received escalating doses of afatinib and selumetinib according to a 3+3 design starting with 20 mg afatinib once daily (QD) continuously and 25 mg selumetinib twice daily (BID) in a 21 days on/7 days off schedule. Continuous and intermittent dosing were explored to assess optimal exposure and tolerability. The primary aim was determining the RP2R. Secondary objectives included assessment of anti-tumor activity and the analyses of pharmacokinetic and pharmacodynamic parameters for target inhibition. Clinicaltrials.gov identifier: NCT2450656. Results: In total, 26 mostly heavily pretreated patients with CRC (n=19), NSCLC (n=6) and pancreatic cancer (n=1) were enrolled among 5 dose-levels. Dose-limiting toxicities (DLTs) occurred in 6 patients and consisted of grade 3 diarrhea (n=3), decreased appetite (n=1), nausea/vomiting (n=1), dehydration (n=2) and mucositis (n=1). Clinical efficacy was limited with no responses according to RECIST v1.1 and stable disease for 221 days in a patient with NSCLC as best response. Conclusions: The RP2R was determined at 20 mg afatinib QD continuously and 25 mg selumetinib BID 21 days on/7 days off for continuous dosing. The 3 patients treated in the escalation cohort of the ongoing intermittent dose-level with 20 mg afatinib QD and 25 mg selumetinib BID 5 days on/2 days off, experienced no DLTs. Pending the latest safety results of the expansion cohort for this ongoing dose-level, the RP2R of intermittent dosing has not been established at the moment. Clinical trial information: NCT2450656 .

89Zr-durvalumab PD-L1 PET in recurrent or metastatic (R/M) squamous cell carcinoma of the head and neck

3573

Background: Immune checkpoint inhibitors (ICI) targeting programmed cell death protein-1/ligand-1 (PD-1/PD-L1) have shown activity in R/M squamous cell carcinoma of the head and neck (SCCHN). Positron-emission-tomography (PET) with 89Zr-labeled anti-PD-L1 antibodies could aid in predicting response to ICI. We present the dose-finding results of the first-in-human 89Zr-durvalumab PD-L1 PET-imaging in patients with SCCHN participating in the ongoing phase II PINCH study (NCT03829007). Methods: Following baseline [18F]FDG-PET and CT/MRI imaging, patients with incurable R/M SCCHN received 37 MBq 89Zr-durvalumab and protein dose 2mg, 10mg or 50mg durvalumab. 89Zr-durvalumab PD-L1 PET-scan was acquired day 5 post-injection. Plasma pharmacokinetic analyses were performed at day 0 and 5. Standardized uptake values (SUV, mean ± SD) were measured in [18F]FDG-positive tumor lesion, liver, spleen, bone marrow and bloodpool. PD-L1-expression was assessed on archival tumor tissue using the Ventana PD-L1 (SP263) assay. Results: 14 patients were enrolled and no adverse events were reported. High tracer-retention was observed in liver and spleen, most prominent in patients receiving 2 or 10mg durvalumab. 89Zr-durvalumab accumulation within tumors and between patients was heterogeneous and not all [18F]FDG-positive lesions showed 89Zr-durvalumab uptake. Tumor lesions were visualized best using 10 or 50mg durvalumab (SUVpeak 2mg: 3.86 ± 0.79, 10mg: 7.46 ± 2.18, 50mg: 5.57 ± 1.74). Tumor-to-blood-ratios for 10mg durvalumab were highest (2mg: 2.27 ± 0.33, 10mg: 3.44 ± 0.76, 50mg: 1.73 ± 0.99; p = 0.019). PK-analyses confirmed visual prolonged tracer-retention in bloodpool with increasing protein dose. PD-L1-expression was equally distributed amongst dose-groups. Conclusions: This is the first study to show feasibility of 89Zr-durvalumab PD-L1 PET in SCCHN patients, demonstrating the highest tumor-to-blood radio with a total dose of 10mg durvalumab. So far, no correlation of tumor PD-L1 expression with 89Zr-durvalumab-uptake and PD-L1 expression on archival tissue was found. Next step will be to correlate 89Zr-durvalumab PD-L1 PET tumor uptake with durvalumab treatment response in the phase 2 part of the PINCH study. Clinical trial information: NCT03829007 .

Prediction of watchful waiting in newly diagnosed metastatic clear cell renal cell carcinoma patients with a good or intermediate prognosis

5079

Background: In metastatic clear cell renal cell carcinoma (mccRCC), the number of International Metastatic Database Consortium (IMDC) risk factors plus metastatic sites may identify patients with rapid or slow disease progression in a period of watchful waiting (WW) (median WW of 8.4 vs 22.2 months; Rini et al. Lancet Oncol. 2016). We aimed to validate this and prospectively assess the added value of baseline PET with [18F]FDG and [89Zr]Zr-DFO-girentuximab to predict the WW-period in the multicenter IMaging PAtients for Cancer drug selecTion (IMPACT)-RCC cohort study. (NCT02228954). Methods: Between February 2015 and March 2018, 40 treatment-naïve mccRCC patients with a good (n=13) or intermediate prognosis (n=25) according to IMDC, were enrolled. Following baseline CT, [18F]FDG and [89Zr]Zr-DFO-girentuximab-PET, CT scans (RECIST1.1) were acquired at 2, 4, 6, 9, 12 months and thereafter every 4 months. Primary endpoint was time to radiological and/or clinical disease progression, requiring systemic treatment. Patients were assigned to a favorable (<2 IMDC risk factors and <3 metastatic sites) or unfavorable for WW-group (all others; Rini et al). Maximum standardized uptake values (SUVmax) were measured in PET-positive lesions measuring ≥10mm, or 15mm in lymph nodes. High and low-uptake groups were defined based on median geometric mean (gm) SUVmax across patients. A one-sided test was used to validate observations by Rini et al; other tests were two-sided. Results: The median WW-period was 9.3 months in the unfavorable WW-group (n=19) vs 20.4 months in the favorable WW-group (n=21) (HR 1.89 95%CI 0.94-3.89; p=0.037), confirming observations of Rini et al. Patients with high [18F]FDG uptake had a median WW-period of 8.5 months compared to 25.2 months in the low-uptake group (HR 4.08 95%CI 1.89-9.28; p=0.0002). Patients with high [89Zr]Zr-DFO-girentuximab uptake had a median WW-period of 10.7 versus 16.4 months in the low-uptake group (HR 1.37; 95%CI 0.69-2.76; p=0.37). [18F]FDG uptake groups improved a Cox-model for WW based on the prognostic groups of Rini et al (p=0.0015); [89Zr]Zr-DFO-girentuximab did not (p=0.98). Conclusions: The IMPACT-RCC study validated the observations by Rini et al. and shows that adding baseline [18F]FDG PET further improves the prediction of the duration of the WW-period in mccRCC patients. Clinical trial information: NCT02228954 .

A phase II study on the efficacy and toxicity of cabozantinib in recurrent/metastatic salivary gland cancer patients

6529

A phase II study on the efficacy and toxicity of cabozantinib in recurrent/metastatic salivary gland cancer patients. Background: Because c-MET and VEGFR are often overexpressed in salivary gland cancer (SGC), this study evaluated the efficacy and safety of cabozantinib in recurrent/metastatic (R/M) SGC pts. Methods: A single center, single arm, phase II study was conducted. Immunohistochemical c-MET positive (H-score ≥10) R/M SGC pts were included in 3 cohorts: adenoid cystic carcinoma (ACC), salivary duct carcinoma (SDC), and other SGCs. Objective growth or complaints due to the disease were required before inclusion in the ACC and other SGC cohort. No prior systemic treatments were required. Pts started 60 mg cabozantinib tablets OD. Primary endpoint was the objective response rate (ORR). A Simon two-stage design was used. In case of ≥1 objective response in the first 9 pts/cohort, 8 additional pts would be included in the cohort. Results: In total 25 pts were included from Sep. 2018 until premature closure due to severe toxicity in Nov. 2019. Median age was 56 years (range 49-72), prior treatments included: primary tumor resection ( n=19), radiotherapy ≥50Gy ( n=24), systemic therapy ( n=10; adjuvant in 2 pts, palliative in 8 pts). Six pts had grade 3 ( n=4), grade 4 ( n=1), or grade 5 ( n=1) wound/fistula complications, occurring at a median of 7.2 mths on cabozantinib (range 2.1-12.8). This resulted in a severe wound complication rate of 32% in 19 pts on treatment for ≥2 mths. Remarkably, 4 out of 6 pts developed this complication in the area exposed to high-dose Rx; 2/4 had a pre-existing fistula in this area. Median interval between Rx and start of cabozantinib was 71.3 mths (range 10.6-94.7). Other grade ≥3 adverse events in >1 pt were: hypertension (5 pts), diarrhoea (2 pts) and dehydration (2 pts). Current median follow-up is 6.8 mths. The ORR was 6% (1/17 pts) in the ACC cohort, 20% (1/5 pts) in the SDC cohort, and 0% (0/3 pts) in other SGC pts; median PFS is 12.6 mths (95% CI 6.8 – 18.4 mths), 9.0 mths (insufficient events for 95% CI), and 6.9 mths (95% CI 0 – 15.2 mths), respectively. Median OS is not reached in any cohort. Conclusions: This phase II study on cabozantinib in R/M SGC pts demonstrated severe wound and fistula complications in 32% of pts on treatment for ≥2 mths, mostly (4/6 pts) within the radiotherapy field. Because of this toxicity the study was closed prematurely. Furthermore, cabozantinib showed minimal clinical activity in SGC pts. Research funding: Ipsen Pharmaceuticals Clinical trial information: NCT03729297 .

The impact of gastric acid suppressive agents on pazopanib exposure

e16076

Background: Pazopanib has been registered for advanced soft tissue sarcoma (STS) and metastatic renal cell carcinoma (mRCC). The uptake of pazopanib is 40% reduced when a proton pump inhibitor is concomitantly used. Nevertheless, still a large group of cancer patients need a form of gastric acid suppressive agents (GAS, e.g. proton pump inhibitors or H2-anagonists) due to gastrointestinal adverse events. Recently, it was demonstrated that the use of pazopanib with GAS resulted in shorter overall survival and progression free survival in patients with STS. In order to limit the effect of GAS on pazopanib absorption, the advice is to take the GAS 1 hour after pazopanib. In that way the pazopanib is dosed at the lowest gastric pH value. However, the effect of this most optimal controlled intake on pazopanib absorption is unknown. Therefore, we investigated whether this controlled intake algorithm affects pazopanib exposure. Methods: In the DIET study, pazopanib trough concentrations (Ctrough) were measured at predefined moments. In this study a total of 80 patients with mRCC and STS were included. The concomitant use of GAS was recorded and taken according the intake algorithm. Patients were subdivided into two groups (with GAS or without GAS). Results: Of the 80 patients, 22 patients were treated with pazopanib in combination with GAS. In patients treated with pazopanib without GAS the geometric mean(GM) pazopanib Ctrough level was 29.1 mg/L (95% CI 26.4 -31.8) compared to 22.4 mg/L (95% CI 18.0-27.8) (p = 0.01) in those treated with GAS. Conclusions: Patient who use pazopanib with controlled intake of GAS had a 23% lower pazopanib exposure. Therefore, we advice that in patients, who are unable to quit their GAS agent, pazopanib trough concentrations should be monitored in order to prevent shorter treatment benefit. Clinical trial information: NCT02138526.

A reduced pazopanib dose with food: Is it more patient-friendly and does it reduce drug costs?

4564

Background: Pazopanib has been licensed for advanced soft tissue sarcoma and metastatic renal cell carcinoma in a fixed oral daily dose of 800mg taken fasted. We hypothesized that ingesting pazopanib with food may improve patients’ comfort and reduce gastro-intestinal adverse events. Moreover, a food intervention, resulting in a better absorption, can lead to a lower dose, which could significantly reduce treatment costs. Methods: Part 1 of the study was performed to determine whether 600mg pazopanib taken with a continental breakfast was bioequivalent to 800mg pazopanib taken fasted. In part 2, differences in GI-toxicity and patient satisfaction were assessed by the cancer-therapy-satisfaction-questionnaire after both intake regimens. Finally, patient’s preference for either intake regimen was asked. Results: 16 patients were included in the bioequivalence study. The geometric mean ratio (fed/fasted) of the area under the plasma concentration time curve was 1.10 (90% CI 1.00-1.19), maximum peak concentration was 1.12 (90% CI 1.02-1.22) and pazopanib trough concentration was 1.10 (90% CI 1.02-1.18). In part 2, 60 patients were included. No differences were seen in the occurrence of GI-toxicities under both intake regimens. Patients seem to be more positive about their feelings about side effects (72.3(95% CI 68.1-76.5) vs 68·2 (62.7-73.6); p=.092) and satisfaction with therapy scores were higher (84.7(95% CI 81.4-87.9) vs 81.9 (78.7-85.2); p= .059) when pazopanib was taken with food. 41 (68%) of the patients preferred the intake with continental breakfast. Conclusions: Intake of 600mg pazopanib with food results in bioequivalent exposure and was preferred over a standard pazopanib dose without food. Moreover, with this simple food intervention a large cost reduction can be realized in patients treated with pazopanib. Clinical trial information: NCT02138526.

Phase Ib (COSMIC-021) trial of cabozantinib (C) in urothelial carcinoma (UC) or C in combination with atezolizumab (A) in patients (pts) with UC, castrate resistant prostate cancer (CRPC) or renal cell carcinoma (RCC)

TPS683

Background: C is an inhibitor of tyrosine kinases involved in tumor growth, angiogenesis, and immune regulation, including MET, VEGFR, and TAM kinases (Tyro3, AXL, MER). Preclinical and clinical studies suggest that C promotes an immune-permissive tumor environment which may enhance response to immune checkpoint inhibitors (ICI) such as the anti-PD-L1 mAb, A. C is approved for pts with advanced RCC and has shown encouraging clinical activity in combination with a PD-1 targeting mAb in RCC, UC, and CRPC (Nadal et al 2017). A is approved for pts with advanced UC after prior platinum-containing chemo and for chemo-naïve pts with platinum ineligible UC or PD-L1+ cisplatin ineligible UC. Combination of C with A may enhance treatment efficacy in pts with genitourinary (GU) cancers. Here, we present the study design of an ongoing phase 1b trial of C + A which includes cohorts with advanced RCC, UC, and CRPC. Methods: This global multicenter, phase 1b, open-label trial will assess the safety, tolerability, activity, and pharmacokinetics of C or C + A (NCT03170960). The study comprises a dose-escalation stage and an expansion stage. The dose-escalation stage (3+3 design) is completed. C 40 mg qd + 1200 mg A q3w is the recommended dose for the expansion stage. In the expansion stage, 18 cohorts (each 30 pts) will be enrolled including 7 cohorts with GU cancers: (1) treatment naïve clear cell RCC; (2) non-clear cell RCC, treatment naïve or following systemic anticancer therapy; (3) UC after prior platinum-based therapy; (4) treatment naïve cisplatin-ineligible UC; (5) treatment naïve cisplatin-eligible UC; (6) UC after prior ICI therapy and (7) CRPC after prior enzalutamide and/or abiraterone. In addition, an exploratory cohort (30 pts) will evaluate single agent 60 mg C in pts with UC after prior ICI therapy. Pts will continue treatment as long as they experience clinical benefit per investigator or until unacceptable toxicity. The primary objective of the expansion stage is the objective response rate per RECIST 1.1 per investigator for each cohort. Secondary objectives will assess safety including immune related AEs. Clinical trial information: NCT03170960.

Effect of crizotinib on disease control in patient with advanced papillary renal cell carcinoma type 1 with MET mutations or amplification: Final results of EORTC 90101 CREATE

580

Background: Papillary renal cell carcinoma type 1(PRCC1) is associated with MET alterations. Our phase II trial assessed the efficacy and safety of crizotinib in patients (pts) with advanced/metastatic PRCC1 with/without MET mutations( MET+, MET-). Methods: Eligible pts with reference pathology-confirmed PRCC1 received oral crizotinib 250mg twice-daily. Pts were attributed to MET+/ MET- sub-cohorts by sequencing of MET exons 16-19 in tumour tissue. Primary endpoint was objective response rate (ORR). If at least 2 of the first 12 eligible/evaluable MET+ pts achieved a confirmed partial (PR) or complete response (RECIST 1.1), a maximum of 35 pts were enrolled. Other endpoints included duration of response (DOR), disease control rate (DCR), progression-free survival (PFS) and rate (PFSR), overall survival (OS) and safety. Results: 23 of 41 pts consenting were eligible, treated and evaluable. In 4 MET+ pts, 2 achieved a PR and 1 had stable disease (SD) (ORR 50%; 95% CI: 6.8-93.7%), DOR was 666 and 1138 days, 1-year PFSR was 75.0% (12.8-96.1%), 1-year OS: 75.0% (12.8-96.1%). Among 16 MET- pts, 1 achieved a PR lasting 302+ days and 11 had SD (ORR: 6.3%; 0.2-30.2%), 1-year PFSR: 27.3% (8.5-50.4%), 1-year OS: 71.8% (41.1-88.4%). Among 3 pts with unknown MET status ( MET?) due to technical failure, 1 achieved a PR lasting 211+ days and 1 had SD (ORR 33.3%, 0.8%-90.6%), 1-year PFSR: 66.7% (5.4-94.5%), 1-year OS: 100%. MET amplification was found post hoc in 1 MET+ (PR, DOR: 1138 days) and 1 MET- case (SD). Common treatment-related AEs were oedema (47.8%), fatigue (47.8%), nausea (39.1%), diarrhoea (39.1%), and blurred vision (34.8%). Conclusions: Crizotinib is active and well tolerated in advanced, metastatic PRCC1, achieving objective responses and long-lasting disease control in pts with MET mutations or amplification. Sporadic, durable responses are also seen in MET-/ MET? cases, suggesting the presence of other alterations of MET or alternative pathways. Clinical trial information: NCT01524926.

Pharmacokinetics of cetuximab and tumor uptake of 89Zr-cetuximab as potential predictive biomarkers for benefit of cetuximab in patients with advanced colorectal cancer

e15117

Background: One third of patients with RAS wild-type metastatic colorectal cancer (mCRC) do not benefit from anti-EGFR inhibitors. Thus, predictive biomarkers to identify patients with primary resistant mCRC are urgently needed. Methods: Patients with chemotherapy refractory mCRC received 500 mg/m2 cetuximab 2-weekly (NCT02117466 and NCT01691391). Patients underwent a 89Zr-cetuximab PET/CT 6 days post-injection after a therapeutic dose of cetuximab. In case of lack of tumor targeting on 89Zr-cetuximab PET, the cetuximab dose was escalated. Pharmacokinetic (PK) analyses included 89Zr-cetuximab plasma levels, EGFR saturation in skin, soluble EGFR (sEGFR), and tumor uptake and biodistribution on 89Zr-cetuximab PET. We defined treatment benefit as response or stable disease (according to RECIST v1.1) at 2 months. Results: Of the 44 patients, median age was 64 years, 25% had a right-sided primary tumor, 5 patients had a BRAF mutated (mt) tumor and 62% had treatment benefit. Cetuximab treatment dose was escalated to maximally 1250 mg/m2 in 8 patients. Visual and semiquantitative data of 89Zr-cetuximab uptake in the tumor, biodistribution and plasma activity 6 days post-injection were not correlated with treatment benefit. Although EGFR saturation in skin after 2 cycles cetuximab had a wide range (21 – 98%), saturation did not correlate with treatment benefit. On-treatment levels of sEGFR were higher than baseline (median 4.1 vs 2.0 ng/ml; p < 0.001), but levels and change of sEGFR did not correlate with PK or treatment efficacy. PFS and OS correlated with right-sided mCRC (p < 0.001 and p = 0.002 respectively) and the presence of a BRAF mt (p < 0.001 and p = 0.004 respectively). In a multivariate Cox-regression only BRAF mt remained correlated with PFS and OS (p = 0.003 and p = 0.027). Conclusions: Interpatient variances in PK and tumor uptake of 89Zr-cetuximab as performed in this setting do not predict treatment benefit of cetuximab in patients with mCRC. In contrast, BRAF status correlated with treatment benefit and warrants further research to confirm the predictive value. Clinical trial information: NCT02117466 and NCT01691391.

Cost-effectiveness of prophylactic antibiotics to prevent pneumonia in patients treated with chemoradiotherapy (CRT) for locally advanced head and neck carcinoma (LAHNC)

6075

Background: Recently, we reported about a prospective randomized study (PANTAP-study) investigating the effect of prophylactic antibiotics in LAHNC pts treated with CRT. We did not show a reduction in pneumonias, but did find a significant decrease in the number of hospitalizations. Detailed quality of life (QoL) results have been reported elsewhere. Now we present the results of the cost-effectiveness analysis. Methods: A multicenter study was performed in LAHNC pts treated with CRT, i.e.cisplatin weekly or 3-weekly combined with radiotherapy for 42 or 49 days. The standard treatment group (STG) received no prophylactic antibiotics; the intervention group (IG) received prophylactic antibiotics, i.e. amoxicillin/clavulanic acid, from day 29 until 14 days after completion of CRT. QoL questionnaires, including EQ-5D, QLQ-C30, EORTC Head&Neck35 and PSSHN, were taken before start of CRT, before start of antibiotics, at the end of CRT and at the end of follow up. Costs of hospitalization, prophylactic antibiotics, pain medication and anti-emetics were taken into account for the cost-effectiveness analysis. Results: A total of 94 pts were randomized; 48 pts to the STG and 47 pts to the IG. Between the STG and IG we found a difference per patient in costs of hospitalization of €2076 and €682 (p = 0.03), respectively, but not in the costs for pain medication per patient €78 and €46, respectively, (p = 0.382). The total costs of hospitalization in combination with prophylactic antibiotics, pain medication and anti-emetics were €2462 and €1037 (p = 0.046) in the STG and IG respectively, leading to a difference in total costs per patient of €1425 in favor of the IG. There were no significant differences in QoL between the groups. Conclusions: Prophylactic antibiotics during CRT for LAHNC did not reduce the rate of pneumonias, but reduced the number of hospitalizations in the IG, which led to a significant reduction in costs. Given the lack of adverse clinical effects, the same QoL, the cost savings and the impact of costs of hospitalization on health care globally, we recommend the use of prophylactic antibiotics in LAHNC pts receiving CRT. Clinical trial information: NCT01598402.

Phase 1b/2 trial of ribociclib+binimetinib in metastatic NRAS-mutant melanoma: Safety, efficacy, and recommended phase 2 dose (RP2D)

9519

Background: Simultaneous inhibition of MEK and CDK4/6 may suppress MAPK pathway activation and cell-cycle checkpoint dysregulation in NRAS-mutant melanoma, resulting in enhanced antitumor activity. Phase 1b data are reported. Methods: The phase 1b primary objective was to determine maximum tolerated dose (MTD)/RP2D. A 28-d cycle of oral ribociclib (RIBO) once daily (QD) for 21 d + oral binimetinib (BINI) twice daily (BID) for 28 d, and a 21-d cycle of RIBO QD + BINI BID, both for 14 d per cycle, were evaluated. Secondary objectives were to evaluate efficacy, safety and pharmacodynamics. Results: Based on dose escalation (van Herpen, ESMO 2015), MTD was 600mg RIBO/45mg BINI for the 21-d and 200/45 for the 28-d regimens. Due to promising activity, the 28-d cycle was selected as RP2D(unconfirmed partial response [PR] with limited follow-up occurred in 35% of pts). This finding was supported by comparable and manageable safety and the Bayesian logistic regression model.As of Jan 2017, the RP2D was received by 16 pts in phase 1b (ECOG PS 0/1/2, 63%/31%/6%; elevated lactate dehydrogenase, 44%; stage IVM1c disease, 50%; prior ipilimumab [ipi], 44%; prior anti–programmed death [PD]-1/PD-L1, 31%). Median (range) exposure was 4 (0–13) mo. Common adverse events (AEs) were increased blood creatine phosphokinase, elevated AST, peripheral edema, acneiform dermatitis, diarrhea and fatigue. Common grade 3/4 AEs were elevated AST and ALT (19%/6%), nausea (19%/0%), rash (19%/0%), vomiting (6%/6%) and neutropenia (12%/0%). Confirmed PR (cPR) occurred in 4 pts (25%; time to response, 48–168 d), stable disease in 7 pts (44%), disease progression in 3 pts (19%); 2 pts (12%) were not evaluable. Among cPR pts, 3 had prior ipi and/or anti–PD-1/PD-L1. Median progression-free survival (mPFS) was 6.7 (95% CI, 3.5–9.2) mo. Sequence analysis of synchronous non- RAS genetic alterations will be presented. Conclusions: Combined RIBO/BINI at the selected RP2D had a manageable safety profile and favorable efficacy (based on mPFS) for NRAS-mutant melanoma in phase 1b. Based on these promising data, the phase 2 expansion is underway to assess antitumor activity at the RP2D. Clinical trial information: NCT01781572.

Change in metabolic tumor activity on 18F-FDG PET after a single dose of cetuximab to predict for treatment benefit, PFS, and OS in patients with advanced colorectal cancer

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Background: Despite RAS selection, one third of patients with metastatic RAS wild-type colorectal cancer (mCRC) do not benefit from anti-EGFR inhibitors. Therefore, an additional or more accurate predictive biomarker is needed to identify patients with primary resistant mCRC. Methods: In the IMPACT-CRC trial (NCT02117466) patients with chemotherapy refractory mCRC received 500 mg/m2 cetuximab every 2 weeks. Before the first dose and just before the second dose, patients underwent a 18F-FDG PET/CT (FDG PET). PET scans were quantitatively assessed by manual tumor delineation of ≤ 5 lesions, 2 per organ. Outcome is reported in total lesion glycolysis (TLG), defined as metabolic tumor volume times mean standard uptake value of the tumor. An optimal threshold to assess metabolic response was defined as decrease in TLG ≥15%. Quantitative data were correlated with CT evaluation after 8 weeks of treatment according to RECIST v1.1. Results: Out of 35 patients, 1 was excluded due to an infusion reaction. Median age was 64 years, 74% was male, 4 patients had a BRAF mutated tumor and 9 patients had right-sided primary tumors. 62% of patients had stable disease or partial response on CT after 8 weeks. At the time of this analysis, 88% of patients had progressive disease and 71% had died. Of the patients with right-sided tumors 11% had treatment benefit, compared to 80% in the left-sided group (p = 0.001). None of the 9 metabolic non-responders had treatment benefit, whereas 83% of the metabolic responders had treatment benefit according to RECIST v1.1. After adjustment for age, WHO score, BRAF mutation, sex and primary tumor site, FDG PET response remained correlated with PFS and OS (p = 0.002 and p = 0.014). Conclusions: Early evaluation of metabolic response after 1 dose of cetuximab is highly and independently predictive for treatment benefit with a 100% negative predictive value. Implementation of early FDG-PET evaluation in daily clinical practice can prevent unnecessary toxicity, costs of ineffective treatment and allows timely treatment adjustment for patients with mCRC undergoing anti-EGFR treatment. Clinical trial information: NCT02117466.

Induction chemotherapy (IC) with docetaxel/cisplatin/5-fluorouracil (TPF) followed by cisplatin-containing concomitant chemoradiotherapy (CRT) in fit patients with locally advanced head and neck cancer (LAHNC): The CONDOR study—A study of the Dutch Head and Neck Society

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Background: Standard treatment for patients (pts) with LAHNC is concomitant CRT containing cisplatin. In general 70% of the pts receive all planned cisplatin cycles. TPF IC is associated with survival benefit, but has never been studied in combination with standard CRT. We aimed to determine if TPF followed by cisplatin-containing CRT, in 2 different schedules, was feasible. Methods: In this multicenter randomized phase II trial LAHNC pts, PS 0-1, were treated with maximal 4 TPF courses (T 75 mg/m2, P 75mg/m2 and F 750 mg/m2 day 1-5) and thereafter randomized between P 100 mg/m2 on days 1, 22, 43 combined with conventional RT (arm A) or P 40 mg/m2weekly, maximally 6, combined with accelerated RT (arm B). Primary endpoint was feasibility, defined as receiving ≥ 90% of the planned total radiation dose. Based on power analysis 70 pts were needed. Results: Following an interim-analysis, the study was early terminated after inclusion of 65 pts because only 32% of pts could be treated with the full cisplatin dose during CRT after TPF. 81,5% of pts was male, median age was 56 yrs and PS was 0 in 79% and 1 in 21%, primary site: oral cavity (23%), oropharynx (57%), hypopharynx (12%), larynx (8%). 3 pts did not start TPF; 6/62 pts were not randomized after TPF, due to death (1), toxicity (3) or severe PD (2). RR after TPF was CR 4%, PR 64% and SD 28% in the randomized pts. 27 pts were randomized in arm A and 29 in arm B. 97% of the pts received at least 90% of the planned total radiation dose. However, in arm A only 6 of the 27 pts (22%) and in arm B 12 of the 29 pts (41%) received the total planned chemotherapy part of the CRT. Most common grade 3-4 toxicity during TPF was febrile neutropenia (18%),and during CRT arm A vs arm B dehydration (26% vs 14% ), dysphagia (26% vs 24%), mucositis (22% vs 57%) and creatinin increase (19% vs 3%). After a median follow-up of 21 (7-42) months 66% of the pts was still alive. Conclusions: After TPF IC cisplatin-containing concomitant CRT is not feasible in LAHNC, because the total planned dose of cisplatin could only be administered in 32% of the pts due to severe toxicity. Clinical trial information: NCT00774319.