Discussion
We reported a patient with stage IVB ICC who was treated with pemigatinib. Liquid CGP was useful for detecting FGFR2 gene fusion. Furthermore, the patient experienced typical pemigatinib side effects requiring treatment; however, long-term survival could still be achieved by multidisciplinary management of side effects. CGP has been approved and used in clinical practice. When conducting CGP, detection rates of mutations in the tissue CGP were higher than those in the liquid CGP (13). However, previous anticancer treatment may have caused tumor heterogeneity and post-treatment specimen collection may not provide adequate specimens for CGP (14). Conversely, liquid CGP can detect gene mutation regardless of tumor heterogeneity and may be more useful as the CGP test than tissue CGP in some cases (15). In this case, liver tumor and lymph node samples were inappropriate for tissue CGP; however, liquid CGP was useful for detecting gene mutation and FGFR2 fusion. Therefore, tumor and time heterogeneity should be considered in performing CGP, and an appropriate method should be used (16,17). New drugs targeting genetic mutations in ICC, such as entrectinib, neurotrophic tyrosine receptor kinase inhibitor or ivosidenib, and isocitrate dehydrogenase 1 inhibitor, have also been approved in recent years (18,19). Genetic mutations may change during treatment. Therefore, accurate timing and frequency of performing CGP should also be verified in the future (16,17). Reports on the use of pemigatinib for ICC in the real-world setting are limited. Pemigatinib has characteristic side effects, for example, nail disorders, taste disorders and hyperphosphatemia as in this case. The pemigatinib doses should be reduced due to severe side effects, such as nail and taste disorders. However, the patient continued the pemigatinib treatment through multidisciplinary treatment. Newly developed anticancer drugs may cause different side effects from conventional anticancer drugs. In this case, side effects required a dose reduction; however, multidisciplinary management enabled the patient to continue treatment, which achieved a long-term survival of approximately 26 months. Thus, a multidisciplinary team that can contribute to a good response and prolonged survival should be established.
In conclusion, we managed a patient treated with pemigatinib. Liquid CGP is useful for detecting FGFR2 fusion. Pemigatinib caused typical side effects, including nail disorders, hyperphosphatemia, and taste disorders; however, multidisciplinary treatment enabled us to continue the treatment and achieve long-term survival.