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.