Monitoring
Relapses affect the liver and peritoneum and rarely
the bone. The risk of relapse is high with ruptured tumors. Evaluate tumor
response by checking for tumor shrinkage, tumor density changes on CT scan, and
absence of tumor progression. For gastrointestinal stromal tumors with a size
of <2 cm without high-risk EUS features, consider endoscopic surveillance
every 6-12 months.
Post-Surgery
Completely Resected Tumors with or
without Preoperative Imatinib
Monitoring for patients with completely resected
tumors with or without preoperative Imatinib includes clinical evaluation
(history and physical examination) every 3-6 months for 5 years, then annually.
For high-risk tumors, evaluation is done every 3 months. It may be less
frequent for small tumors (<2 cm). Abdominal or pelvic CT scan should be
requested every 3-6 months for 3-5 years, then annually. It may be less
frequent for small tumors (<2 cm) or low-risk disease, and more frequently
for patients with high-risk disease who discontinue TKI treatment.
Incompletely
Resected Tumors
For incompletely
resected tumors, CT and/or MRI should be done every 3-6 months for 3-5 years.
Metastatic Disease or Persistent
Gross Residual Disease with or without Preoperative Imatinib
Monitoring for patients with metastatic disease or
persistent gross residual disease with or without preoperative Imatinib
includes clinical evaluation and abdominal or pelvic CT scan every 3-6 months. It
may be less frequent for small tumors (<2 cm).
Definition
of Resistance
Primary Imatinib
resistance is the evidence of development of clinical progression during the
first 6 months of Imatinib treatment. It is most often observed in patients
with KIT exon 9 mutations under Imatinib 400 mg daily therapy, PDGFRA
D842 mutations or those with tumors without mutations in KIT or PDGFRA,
majority of which are SDH-deficient tumors. Secondary resistance is observed in
patients who are on Imatinib for >6 months with an initial response or
disease stabilization followed by progression. It is due to the outgrowth of
the tumor clones with secondary mutations in KIT.
Management of Disease
Progression
Progression is the appearance of a new lesion or an
increase in tumor size which may be determined by abdominal or pelvic CT or MRI
with clinical interpretation.
Limited Disease Progression
For gastrointestinal stromal tumors which become
Imatinib-resistant, continue or increase Imatinib dose as tolerated or may
change to Sunitinib and reassess the tumor response via PET or CT scan. It is
most effective in patients with KIT exon 9 mutation. For progressing
lesions while continuing Imatinib, consider surgical resection if still
feasible, radiofrequency ablation (RFA), embolization or chemoembolization, or
palliative radiation therapy (RT) for symptomatic lesions. For gastrointestinal
stromal tumors which become Avapritinib-resistant, continue Avapritinib and
consider surgical resection if feasible, or ablation, embolization or
chemoembolization, or palliative RT for symptomatic lesions.
Generalized
Disease Progression
For gastrointestinal
stromal tumors which become Imatinib-resistant, increase Imatinib dose as
tolerated and assess response via PET or CT scan. Another option is to switch
to alternate TKI (eg Sunitinib) in patients with performance status of 0-2. If
still with limited or systemic disease progression, consider Regorafenib, a
clinical trial or supportive care.
For gastrointestinal
stromal tumors which become Avapritinib-resistant, switch to alternative TKI
patients with performance status 0-2.
Clinical
Trial
Clinical trial is
recommended for patients with progressive disease despite prior therapies. It
is also recommended for patients with mutations resistant to Avapritinib,
Imatinib, Regorafenib, Ripretinib, and Sunitnib.
Best
Supportive Care
Best supportive care is a
recommended option for progressive disease despite other therapies.