Recent Updates on Mechanisms of Resistance to 5-Fluorouracil and Reversal Strategies in Colon Cancer Treatment

5-Fluorouracil (5-FU) plus leucovorin (LV) remain as the mainstay standard adjuvant chemotherapy treatment for early stage colon cancer, and the preferred first-line option for metastatic colon cancer patients in combination with oxaliplatin in FOLFOX, or irinotecan in FOLFIRI regimens. Despite treatment success to a certain extent, the incidence of chemotherapy failure attributed to chemotherapy resistance is still reported in many patients. This resistance, which can be defined by tumor tolerance against chemotherapy, either intrinsic or acquired, is primarily driven by the dysregulation of various components in distinct pathways. In recent years, it has been established that the incidence of 5-FU resistance, akin to multidrug resistance, can be attributed to the alterations in drug transport, evasion of apoptosis, changes in the cell cycle and DNA-damage repair machinery, regulation of autophagy, epithelial-to-mesenchymal transition, cancer stem cell involvement, tumor microenvironment interactions, miRNA dysregulations, epigenetic alterations, as well as redox imbalances. Certain resistance mechanisms that are 5-FU-specific have also been ascertained to include the upregulation of thymidylate synthase, dihydropyrimidine dehydrogenase, methylenetetrahydrofolate reductase, and the downregulation of thymidine phosphorylase. Indeed, the successful modulation of these mechanisms have been the game plan of numerous studies that had employed small molecule inhibitors, plant-based small molecules, and non-coding RNA regulators to effectively reverse 5-FU resistance in colon cancer cells. It is hoped that these studies would provide fundamental knowledge to further our understanding prior developing novel drugs in the near future that would synergistically work with 5-FU to potentiate its antitumor effects and improve the patient's overall survival.

Immunomodulatory nanomedicine for colorectal cancer treatment: a landscape to be explored?

Colorectal cancer (CRC) is one of the deadliest cancers in the world mainly due to metastasis events. Despite improvements, the available treatment modalities for metastatic cases are limited, being generally associated with poor prognosis. As is well known, the immunosuppressive tumor microenvironment (TME) plays a key role in tumorigenesis, promoting cancer cell immune escape and disease progression. In addition, accumulating evidence indicates that the immunosuppressive microenvironment is a critical barrier for antitumor immunity in CRC, being extremely important to modulate the immune microenvironment to inhibit the tumor-promoting immune response. Therefore, new and effective cancer immunotherapeutic approaches demand a better control over the TME to reverse these immunosuppressive conditions. According to the features of different nanomedicines, nanoparticles can constitute a promising strategy, using different materials with the inherent ability to modulate TME and also with the potential to target immunosuppressive cells, to deliver antigens or immunomodulatory agents to eliminate this tumor. In this review, we summarize the importance of the TME in the progression and treatment response of CRC, exploring the potential of the nanotechnology for the development of immunomodulatory therapeutic strategies.

Appropriateness of trifluridine/tipiracil in the clinical practice of third-line therapy in metastatic colorectal cancer

Aim: To help to remove misperception of an appropriate position of trifluridine/tipiracil (FTD/TPI) in the treatment of metastatic colorectal cancer. Materials & methods: The RAND Corporation/UCLA Appropriateness Method was used by a panel of Italian experts to develop recommendations concerning daily practice with FTD/TPI. Forty-three clinical scenarios were discussed in two rounds and the resulting statements were rated as appropriate, uncertain or inappropriate, according to the median score. Results: Several topics were dealt with, covering the profile of eligible patients, therapeutic options beyond the second line, the practice of treatment with FTD/TPI, evaluation and efficacy and toxicity, as well as costs and compliance. Conclusion: FTD/TPI is an important therapeutic resource in refractory metastatic colorectal cancer that combines manageability and safety.

Trifluridine/tipiracil: A practical guide to its use in the management of refractory metastatic colorectal cancer in Australia

Trifluridine/tipiracil is available on the Australian Pharmaceutical Benefits Scheme for the treatment of patients with metastatic colorectal cancer (mCRC) previously treated with, or not considered candidates for, fluoropyrimidine-, oxaliplatin- and irinotecan-based chemotherapies, anti-vascular endothelial growth factor agents and anti-epidermal growth factor receptor agents. This article reviews trifluridine/tipiracil clinical data and presents practical information on its use in the management of refractory mCRC in Australia. Whereas the primary mechanism of action of fluoropyrimidines such as fluorouracil (5-FU) and capecitabine is enzyme inhibition of nucleotide synthesis, trifluridine/tipiracil primarily acts by incorporation into DNA, resulting in DNA dysfunction. Trifluridine/tipiracil has activity in patients with 5-FU-resistant tumors and can be considered in patients with prior intolerance or toxicity to 5-FU. In the pivotal phase III RECOURSE trial evaluating trifluridine/tipiracil in chemotherapy-refractory mCRC, efficacy benefits were observed across all a priori prognostic subgroups including those defined by age (≥65 and ≥75 years), geographical origin, primary tumor site or KRAS status. Trifluridine/tipiracil therapy benefits appropriately selected patients who have an ECOG performance status of 0 or 1, with no more than mild hepatic impairment or mild-to-moderate renal impairment, and who are capable of adhering to oral therapy safely. Appropriate dosing, monitoring for adverse events and effective management of side effects are essential.

Metastatic Colorectal Carcinoma after Second Progression and the Role of Trifluridine-Tipiracil (TAS-102) in Switzerland

BACKGROUND

Metastatic colorectal carcinoma (mCRC) is one of the most prevalent types of cancer worldwide. After tumor progression with first- and second-line treatment, trifluridine (FTD) and tipiracil (TPI) has been shown to be a treatment option.

SUMMARY

Data from a pivotal phase 3 trial (RECOURSE) and an ongoing phase 3b trial (PRECONNECT) have shown that, in mCRC patients who experienced disease progression after 2 lines of standard therapy, treatment with FTD/TPI is safe and efficacious. Other third-line options include regorafenib, rechallenge with previous treatment lines or personalized approaches based on comprehensive molecular profiling. Randomized trials or sequential studies aiming for the right treatment sequence or predefined subtypes for FTD/TPI or regorafenib as well for rechallenge are missing. However, FTD/TPI as well as regorafenib are recommended by the current ESMO, German S3, and National Comprehensive Cancer Network (NCCN) guidelines in the same situation, thus offering physicians a number of alternatives for the treatment of mCRC patients after the second progression. Key Message: This narrative review summarizes published data and their impact for FTD/TPI as well for regorafenib and rechallenge chemotherapy in clinical practice settings of refractory situations of colorectal cancer.