Nivolumab treatment for metastatic thymic epithelial tumors

Metastatic and unresectable thymoma (T) or thymic carcinoma (TC) have limited treatment options, especially after first line.

Patients with unresectable or recurrent thymic tumors who used minimum one dose of nivolumab at any line of treatment were evaluated retrospectively. Even though nivolumab was administered 3mg/kg dosage in PRIMER study, due to toxicity and financial concerns, we used low dose regimen mostly.

Among 46 unresectable and recurrent thymic epithelial tumors; 8 patients with TC (n = 3), T (n = 4) and mixt histology (n = 1) were reviewed. Three patients had myasthenia gravis history that had to be controlled before treatment. Four patients showed moderate (n = 2) or severe (n = 2) adverse events with nivolumab treatment. Interestingly, two severe adverse events were occurred at first dose even with 40 mg nivolumab and required cessation of treatment permanently. The median number of nivolumab received was four (range: 1-18). Best response was partial response. Two patients progressed at the 3rd and 5th month of treatment. Best duration of response for one patient with TC and one patient with T-B2 were 9 and 14 months, respectively. Median survival time after nivolumab was 7.4 months (range: 2-22.1).

After the results of the previous study could be supported by randomized prospective studies with more number of patients, nivolumab may be considered as an option in patients with thymic epithelial tumors who have received multiple line treatments. However, given the high rate of severe toxicities, there is need to find out a reliable marker to prediction patients who will derive benefit or exhibit toxicity.