Study to Assess the Effect of Itraconazole (a CYP3A4 Inhibitor) on the Pharmacokinetics of AZD9291, in Patients With EGFR Positive Non-small Cell Lung Cancer. Patients Will be Chosen From Those Who Have Already Been Prescribed an EGFR TKI Medicine (Such as Iressa or Tarceva)

For inclusion in the study, patients should fulfil the following criteria: 1. Male or female, aged at least 18 years. 2. Histological or cytological confirmation diagnosis of NSCLC. 3. Radiological documentation of disease progression while on a previous continuous treatment with an EGFR TKI, eg, gefitinib or erlotinib. In addition, other lines of therapy may have been given. All patients must have documented radiological progression on the last treatment administered prior to enrolling in the study. 4. Confirmation that the tumour harbours an EGFR mutation known to be associated with EGFR TKI sensitivity (including G719X, exon 19 deletion, L858R, L861Q). 5. ECOG performance status 0-1 with no deterioration over the previous 2 weeks. 6. Patients must have a life expectancy of ≥12 weeks as estimated at the time of screening. 7. Evidence of non-childbearing status for women of childbearing potential, or post-menopausal status: negative urine or serum pregnancy test within 28 days of study treatment, confirmed prior to treatment on Day 1 of Part A, or post menopausal status. Females should be using adequate contraceptive measures and must have a negative pregnancy test prior to start of dosing if of child-bearing potential or must have evidence of non-child-bearing potential by fulfilling one of the following criteria at screening: post-menopausal defined as aged more than 50 years and amenorrhoeic for at least 12 months following cessation of all exogenous hormonal treatments; women under 50 years old would be consider postmenopausal if they have been amenorrhoeic for 12 months or more following cessation of exogenous hormonal treatments and with LH and FSH levels in the post-menopausal range for the institution; documentation of irreversible surgical sterilisation by hysterectomy, bilateral oophorectomy or bilateral salpingectomy but not tubal ligation. 8. Male patients should be willing to use barrier contraception, ie, condoms, until 6 months after last study drug is taken. Patients should not enter the study if any of the following exclusion criteria are fulfilled: 1. Participation in another clinical study with an IP during the last 14 days (or a longer period depending on the defined characteristics of the agents used). 2. Treatment with any of the following: Treatment with an EGFR TKI w/in 8 days or approximately 5x half-life, whichever is the longer, of the first dose of study treatment; Any cytotoxic chemotherapy, investigational agents or other anticancer drugs w/in 14 days of the first dose of study treatment; Major surgery (excluding placement of vascular access) within 4 weeks of the first dose; Radiotherapy with a limited field of radiation for palliation within 1 week of the first dose of study treatment, with the exception of patients receiving radiation to more than 30% of the bone marrow or with a wide field of radiation which must be completed within 4 weeks of the first dose of study treatment; Patients currently receiving (or unable to stop use prior to receiving the first dose of study treatment) medications or herbal supplements known to be potent inhibitors of CYP2C8 and of CYP3A4 (at least 1 week prior) and potent inducers of CYP3A4 (at least 3 week prior). All patients must try to avoid concomitant use of any medications, herbal supplements and/or ingestion of foods with known inducer/inhibitory effects on CYP3A4, CYP2C8, and/ or CYP1A2. 3. Any unresolved toxicities from prior therapy greater than CTCAE Grade 1 at the time of starting study treatment with the exception of alopecia and Grade 2, prior platinum-therapy related neuropathy. 4. Any intake of grapefruit, grapefruit juice, Seville oranges, Seville orange marmalade, or other products containing grapefruit or Seville oranges within 7 days of the first administration of the IP until the end of Part A. 5. Spinal cord compression or brain metastases unless asymptomatic, stable and not requiring steroids for at least 4 weeks prior to start of study treatment. 6. Any evidence of severe or uncontrolled systemic diseases, including uncontrolled hypertension and active bleeding diatheses, which in the Investigator's opinion makes it undesirable for the patient to participate in the study or which would jeopardise compliance with the protocol, or active infection including hepatitis B, hepatitis C and human immunodeficiency virus (HIV). Screening for chronic conditions is not required. 7. Inadequate bone marrow reserve or organ function as demonstrated by any of the following laboratory values: ANC \<1.5 x 10\^9/L; Platelet count \<100 x 10\^9/L; Haemoglobin \<90 g/L; ALT \>2.5 x the institutional ULN if no demonstrable liver metastases or \>5 x institutional ULN in the presence of liver metastases; AST \>2.5 x institutional ULN if no demonstrable liver metastases or \>5 x institutional ULN in the presence of liver metastases; Total bilirubin \>1.5 x institutional ULN if no liver metastases or \>3 x institutional ULN in the presence of documented Gilbert's Syndrome or liver metastases; Creatinine \>1.5 x institutional ULN concurrent with creatinine clearance \<50 mL/min (measured or calculated by Cockcroft-Gault formula); confirmation of creatinine clearance is only required when creatinine is \>1.5 x institutional ULN. 8. Any of the following cardiac criteria: Mean resting corrected QT interval corrected for heart rate using Fridericia's correction factor (QTcF) \>450 msec obtained from 3 ECGs; Any clinically important abnormalities in rhythm, conduction or morphology of resting ECG eg, complete left bundle branch block, third degree heart block, second degree heart block, PR interval \>250 msec; Any factors that increase the risk of QTc prolongation or risk of arrhythmic events such as heart failure, hypokalaemia, congenital long QT syndrome, family history of long QT syndrome or unexplained sudden death under 40 years of age or any concomitant medication known to prolong the QT interval. 9. Patients unable to swallow oral medication or patients with GI disorders or significant GI resection likely to interfere with the absorption of AZD9291. 10. Past medical history of interstitial lung disease (ILD), drug-induced ILD, radiation pneumonitis which required steroid treatment, or any evidence of clinically active ILD. 11. Women who are breastfeeding. 12. Patients with a known hypersensitivity to AZD9291 or itranconazole or any of their excipients. 12\. Concomitant medication contraindicated for use with itraconazole (including, but not limited to): cisapride, oral midazolam, nisoldipine, pimozide, quinidine, dofetilide, triazolam, levacetylmethadol (levomethadyl), 3-hydroxy-3-methyl-glutaryl coenzyme A (HMG-CoA)- reductase inhibitors metabolized by CYP3A4, such as lovastatin and simvastatin, ergot alkaloids metabolized by CYP3A4, such as dihydroergotamine, ergometrine (ergonovine), ergotamine and methylergometrine (methylergonovine). 13\. For optional genetic research: Previous allogenic bone marrow transplant or non-leukocyte depleted whole blood transfusion within 120 days of sample collection.