Chemotherapy rechallenge after regorafenib treatment in metastatic colorectal cancer: still hope after the last hope?

Introduction: The introduction of biological agents in cancer therapy is changing the progression of metastatic colorectal cancer. Currently, resistance to biological agents is an emerging problem; the progression of the disease is caused by the development of resistant clones. According to some authors, these clones can be re-sensitized to traditional and previously utilized chemotherapy agents. The results of the CORRECT study demonstrated the efficacy of regorafenib monotherapy in both KRAS wild type and mutant pretreated patients (pts). Two recent reports showed the potential of reintroduction of chemotherapy, even after treatment with regorafenib. Patients and methods: We performed a retrospective review of clinical data from patients treated with regorafenib at our institution between March 2012 and March 2013. We analysed patient characteristics, KRAS/NRAS status, response to treatment (evaluated by RECIST v1.1 criteria) and survival. Results: Regorafenib was administered to 128 patients, and 11 (8.6%) received post-regorafenib therapy (to our knowledge). Seven (63.6%) patients were wild type for KRAS/NRAS. Post-regorafenib therapy represented for all the patients at least the fourth line: all the pts received both oxaliplatin- and irinotecan-based chemotherapy, all of them were treated with bevacizumab, and 7 patients also received cetuximab. Eight patients (72.7%) were treated with standard chemotherapy after regorafenib (irinotecan monotherapy, capecitabine plus oxaliplatin or irinotecan, dacarbazine or raltitrexed), while 3 patients received an experimental therapy (clinical trial). Nine of the 11 (81.8%) patients had PD and 2 patients had SD. The median progression-free survival was 1.6+ months (range 0.5-3.5), the median OS post-regorafenib was 2.1+ months (range 0.5-10.2) and the 6-month OS was 27.3%. Conclusion: Our retrospective analysis showed that after regorafenib therapy, re-introduction of chemotherapy is possible. Unfortunately, we reported a high percentage of disease progression beyond regorafenib, which is likely due to the high percentage of heavily pretreated patients (some received four or five types of therapy before regorafenib). We think that regorafenib could represent a chemotherapy resensitizing agent; however, additional studies are needed in patients who have received less pretreatment.