Stuying the influence of milk on the absorption of erlotinib

1. Age ≥ 18 years

2. Histological or cytological confirmed diagnosis of NSCLC, locally advanced and metastatic disease stage IIIB and IV, for which treatment with erlotinib monotherapy has been initiated (to be evaluated by the treating physician)

3. Use of erlotinib monotherapy for at least 14 days (to guarantee steady-state) and willing to continue the treatment until the end of the study

4. ECOG Performance Status ≤ 1

5. Subject is able and willing to sign the Informed Consent Form prior to screening evaluations

6. No concurrent use of (over the counter) medication or (herbal) supplements known to induce or inhibit CYP3A4, CYP2C8, CYP1A1, CYP2D6, and/or P-glycoprotein

7. No concurrent (over the counter) use of other acid reducing drugs other than esomeprazole 40mg (PPIs, H2As and/or antacids) during the study. Willing to switch to brand name esomeprazole (Nexium®) during the study if on other acid reducing drugs.

8. No concurrent medication or supplements which can interact with esomeprazole or erlotinib

9. Abstain from grapefruit, grapefruit juice, herbal dietary supplements, and herbal tea during the study

10. Willing to take erlotinib with Cow’s milk.

1. Pregnant or lactating patients

2. Impossibility to take oral drugs

3. Serious illness or medically unstable condition requiring treatment, symptomatic CNS metastases or history of psychiatric disorder that would prohibit the understanding and giving of informed consent

4. Patients with proved lactose intolerance and/or cow’s milk protein intolerance.

5. Use of medications or dietary supplements known to induce or inhibit CYP3A4, CYP2C8, CYP1A1, CYP2D6, and/or P-glycoprotein

6. Unwillingness to abstain from acidic beverages (cola), grapefruit (juice), (herbal) dietary supplements, herbals, over-the-counter medication (except for paracetamol and ibuprofen) and other drugs known to seriously interact with esomeprazole and erlotinib during the study period.