Second-line chemotherapy in patients with primary unknown cancer

There are few existing reports on the efficacy of second-line chemotherapy in patients with cancer of unknown primary site (CUP). The aim of this study was to identify characteristics of CUP patients linked to a positive response to chemotherapy.

We retrospectively studied the clinical outcomes of second-line chemotherapy in patients with CUP who had previously been treated with platinum-based first-line chemotherapy.

A total of 27 patients received second-line chemotherapy. Of these patients, 5 (19%) showed an objective response to second-line chemotherapy; 4 of these patients had shown a favorable response to first-line chemotherapy and had a chemotherapy-free interval (CFI) of more than 4.5 months. Among the 8 patients in whom the CFI was more than 4.5 months, 4 (50%) showed an objective response to platinum-based second-line chemotherapy, whereas among the 16 patients with a CFI of less than 4.5 months, only 1 (6%) showed a response to any chemotherapeutic regimen.

The response to second-line chemotherapy in CUP patients who had received platinum-based first-line treatment seemed to be associated with the response to first-line chemotherapy and the CFI. Although it remains unclear whether second-line chemotherapy might contribute to a survival benefit in patients with CUP, patients who show a favorable response to first-line chemotherapy and also a relatively prolonged CFI appear to be likely to benefit from second-line chemotherapy.