This open-label randomized clinical trial aims to evaluate the glutamine plus Lactobacillus reuteri supplementation effect in a standard-of-care diet in EGFR mutant patients with advanced non-small cell lung cancer (NSCLC) under tyrosine kinase inhibitors (TKIs) therapy.

The main question it aims to answer is ¿What is the effect of glutamine plus L. reuteri added to an astringent diet in preventing diarrhea generated by TKI therapy?

Patients will receive an astringent diet supplemented with 10 grams of glutamine and L. reuteri (100 million CFU). Researchers will compare the Glutamine plus L. reuteri diet with a standard astringent diet to see if TKI therapy diarrhea is prevented.

Patients in the experimental group will receive two sachets of Glutapak-R every twelve hours for up to six weeks alongside treating physician-chosen EGFR therapy. Patients in the control group will receive a standard-of-care diet.

All patients will receive nutritional counseling every two weeks.

Inclusion Criteria:

• Both sexes
• ≥ 18 years old
• Pathologically confirmed diagnosis of NSCLC
• Stage IIIB - IV by the American Joint Committee of Cancer Version 8.
• Candidates to receive EGFR-TKI treatment (1st & 2nd generation TKI)
• ECOG score ≤ 2
• Life expectancy > eight weeks
• Signed written informed consent

Exclusion Criteria:

• Patients who cannot attend the first protocol appointment.
• Treatment with other anti-cancer therapy
• Participating in other clinical trials in the former four weeks
• Any other serious condition or uncontrolled active infection, altered mental status or psychiatric disorder that, in the investigator´s opinion, would limit the ability of an individual to meet the requirements of the study or which affects the interpretability of the results.
• Active hepatitis virus infection (any serotype) or chronic infection with a potential risk of reactivation evaluated through a serological panel.
• Active HIV infection.
• Breastfeeding.