Tumor Kinase Inhibitor Concentrations Measured by PET

Inclusion Criteria:

1. Patients must have a histologically confirmed diagnosis of an advanced or metastatic solid malignancy.
2. Patients must have confirmed radiological or clinical progressive disease.
3. Patients must have at least one measurable tumor lesion outside the liver.
4. Indication for standard use of sorafenib or erlotinib
5. Age ≥ 18 years.
6. ECOG Performance Status ≤ 2.
7. Life expectancy of at least 12 weeks.
8. Patients should be able to swallow oral medication.
9. Adequate bone marrow, liver and renal function as assessed by the following laboratory requirements to be conducted within 7 days prior to screening:

   1. Hemoglobin \> 6.0 mmol/L
   2. Absolute neutrophil count (ANC) \>1,5 x 10\*9/L
   3. Platelet count ≥ 100 x 10\*9/L
   4. Total bilirubin \< 2 times the upper limit of normal (ULN)
   5. ALT and AST \< 2.5 x ULN; \< 5x ULN in case of liver metastases, except for patients with hepatocellular carcinoma, than Child Pugh classification A-B.
   6. Alkaline phosphatase \< 4 x ULN; \< 5x ULN in case of liver metastases, except for patients with hepatocellular carcinoma, than Child Pugh classification A-B.
   7. Serum creatinine eGFR ≥ 50 mL/min.
   8. PT-INR/PTT \< 1.5 x ULN, unless coumarin derivatives are used.
   9. Activated partial thromboplastin time \< 1.25 x ULN (therapeutic anticoagulation therapy is allowed, if this treatment can be interrupted for a biopsy as judged by the treating physician).

Exclusion Criteria:

1. Concurrent treatment with other anticancer agents or experimental drugs.
2. History of cardiac disease:

   1. Congestive heart failure \>NYHA class 2.
   2. Active Coronary Artery Disease (defined as myocardial infarction within 6 months prior to screening).
   3. Cardiac arrhythmias requiring anti-arrhythmic therapy (beta blockers or digoxin are permitted).
3. Uncontrolled hypertension. Blood pressure must be ≤160/95 mmHg at the time of screening on a stable antihypertensive regimen. Blood pressure must be stable on at least 2 separate measurements.
4. Uncontrolled infections (\> grade 2 NCI-CTC version 4.0).
5. Subjects with serious non-healing wound, ulcer, or bone fracture.
6. Patients with thromboembolic events within 3 months prior to study inclusion.
7. Significant skin condition interfering with treatment
8. Patients undergoing renal dialysis.
9. Pregnant or breast-feeding subjects. Women of childbearing potential must have a negative pregnancy test performed within 7 days of the start of treatment. Both men and women enrolled in this trial must agree to use adequate barrier birth control measures (e.g., cervical cap, condom, or diaphragm) during the course of the trial. Oral birth control methods alone will not be considered adequate on this study, because of the potential pharmacokinetic interaction between study drug and oral contraceptives. Concomitant use of oral and barrier contraceptives is advised. Contraception is necessary for at least 6 months after receiving the study kinase inhibitor.
10. Concomitant use of dexamethasone, anti-convulsants and anti-arrhythmic drugs other than digoxin or beta blockers.
11. Major surgery within 28 days prior to start of treatment.
12. Medical, psychological or social conditions that may interfere with the subject's participation in the study or evaluation of the study results.
13. Any condition that is unstable or could jeopardize the safety of the subject and their compliance in the study.