2016 Volume 56 Issue 5 Pages 355-360
Background. As the incidence of lung cancer and pulmonary non-tuberculous mycobacterial (NTM) infection is increasing, the incidence of coexistent lung cancer and pulmonary NTM infection is also increasing. Evidence shows that drug interactions can be problematic in the treatment of coexisting lung cancer and pulmonary NTM infection. Gefitinib is normally used to treat lung cancer. However, CYP3A4 inducers, such as rifampicin and rifabutin, reduce the concentration of gefitinib in the blood, whereas CYP3A4 inhibitors, such as clarithromycin, increase its concentration. Consequently, drug interaction is a major problem when gefitinib is used to treat lung cancer in patients with progressive pulmonary NTM infection. Case. A 72-year-old man was diagnosed with stage IV lung cancer. The cancer was pathologically identified as an adenocarcinoma, and a driver mutation of the epidermal growth factor receptor (L858R) was identified. The patient was treated with gefitinib, but he subsequently developed a progressive pulmonary Mycobacterium avium infection. We also identified drug interactions between gefitinib and rifampicin, rifabutin and clarithromycin. The patient's blood gefitinib concentration was measured because combination therapy with these drugs can lead to instability in the concentration of gefitinib and tumor progression. The gefitinib concentration was reduced to 60% of the original concentration following the administration of rifabutin but increased to 130% of the original concentration after the administration of rifabutin, clarithromycin, and ethambutol. However, the patient developed hyperbilirubinemia after the combined administration of rifabutin, clarithromycin, and ethambutol, and as a consequence, the combination therapy was discontinued. Afatinib is a drug that is largely considered to be unaffected by the CYP3A4 metabolism. Thus, afatinib was administered with clarithromycin, ethambutol, and rifampicin; however, the patient experienced side effects and the therapy was discontinued. Conclusion. We herein presented a case of a patient with coexisting lung cancer and pulmonary Mycobacterium avium complex disease, who was treated with gefitinib, rifabutin, clarithromycin, and ethambutol. However, this combination therapy resulted in both drug interactions and side effects. It is therefore very important to consider drug interactions and side effects in the treatment of coexisting lung cancer and pulmonary NTM infection.
