Surgical management after neoadjuvant imatinib therapy in gastrointestinal stromal tumours (GISTs) with respect to imatinib resistance caused by secondary KIT mutations.
BACKGROUND
In metastasized GISTs, resistance to imatinib after initial tumour response has been associated with observation of secondary mutations in the activation loop of KIT. The aim of the current study was to evaluate the tumour response and observance of secondary KIT mutations in a case of GIST undergoing neoadjuvant imatinib therapy.


METHODS
We report on a case of an initially unresectable gastric GIST with curative resection after 10 months of neoadjuvant imatinib therapy. Mutation analysis of KIT was performed on a pretherapeutic biopsy specimen, as well as on the resected tumour specimen.


RESULTS
The pretherapeutic biopsy revealed cKit positive tumour cells with mutation of KIT exon 11 Del 560-576. The remaining tumour mass after neoadjuvant imatinib therapy almost exclusively consisted of hypocellular myxohyalinale stroma with rare microfoci of cKit positive tumour cells. Laser microdissection of several tumour microfoci revealed two additional point mutations located in the activation loop of KIT exon 17, C809G and N822Y, each observed separately in a distinct microfocus. Neither of these two point mutations has been reported in a GIST so far.


CONCLUSIONS
Neoadjuvant imatinib therapy successfully reduces tumour size in GISTs. Since resistance relevant secondary mutations of the activation loop of KIT may be observed after neoadjuvant imatinib therapy, the time elapse with preoperative imatinib therapy should be chosen as short as curative tumour resection or function sparing surgery can be carried out. The determination of the optimal time point for surgery is therefore a critical event and will be discussed.
Haller
Florian
F
Department of Pathology, Georg August University, Robert-Koch-Str. 40, 37099, Göttingen, Germany. florian.haller@med.uni-goettingen.de
Detken
Sven
S
Schulten
Hans-Jürgen
HJ
Happel
Nicole
N
Gunawan
Bastian
B
Kuhlgatz
Jens
J
Füzesi
László
L
D000368:Aged; D000970:Antineoplastic Agents / Q000008:administration & dosage*; D001549:Benzamides; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D005260:Female; D046152:Gastrointestinal Stromal Tumors / Q000188:drug therapy / Q000601:surgery*; D006801:Humans; D000068877:Imatinib Mesylate; D009154:Mutation; D020360:Neoadjuvant Therapy; D010879:Piperazines / Q000008:administration & dosage*; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics*; D011743:Pyrimidines / Q000008:administration & dosage*; D013274:Stomach Neoplasms / Q000188:drug therapy / Q000601:surgery*; D013997:Time Factors
D000970:Antineoplastic Agents; D001549:Benzamides; D010879:Piperazines; D011743:Pyrimidines; D000068877:Imatinib Mesylate; D019009:Proto-Oncogene Proteins c-kit