Pediatric GIST Questions
GIST Support International posed some questions about pediatric GIST to Alberto S. Pappo, MD. Dr. Pappo is a Professor in the Department of Pediatrics, Section of Hematology-Oncology at Baylor College of Medicine. He practices as Head of the Solid Tumor Program at Texas Children's Cancer Center and Hematology Service. You can view a webcast of a presentation Dr. Pappo made at the 2006 ASCO meeting via this link.
Here are Dr. Pappo's answers to our questions.
1. We have read that anemia is often the presenting symptom in children or adolescents with GIST. Are pediatric-type tumors inside the stomach more likely to bleed than adult-type gastric tumors growing outward from the stomach?
I do not know the answer to this question but the most common presenting symptom in children with gastric GIST is gastrointestinal bleeding.
2. Your presentation at ASCO 2006 mentioned a trial for young GIST patients that would start soon (S0146). Are plans for that finalized yet, and what will it entail?
The funding for this trial has been suspended so we are trying to obtain funding from Novartis to at least develop a reGISTRY. Parental support would greatly help!
3. We are aware that pediatric GIST is more likely than adult GIST to metastasize into lymph nodes. Is there any agreement on whether gastric lymph nodes should be removed as a policy, or only if they show metastasis?
Only if they are palpable or suspicious.
4. Are there any data on what percent of non-Carney-Triad pediatric GIST patients may show metastasis? (We know Dr. Carney has published statistics on Triad patients.)
There are no data that I am aware of.
5. Many patients and parents are deeply concerned about cumulative radiation exposure from monitoring scans (both CT and PET) in young patients. In your experience, can MRI detect recurrence or metastasis as accurately as CT, thereby reducing radiation exposure?
To my knowledge, MR is not the modality of choice to follow primary tumors and hepatic metastases in GIST. the most recent National comprehensive Cancer Network meeting decided to recommend CT scan as the gold standard for following patients with GIST. Radiation doses for CT have been significantly reduced by calibrating instruments in pediatric hospitals.
6. What evidence is there regarding the effectiveness of imatinib or sunitinib against pediatric GIST? Is there any role for adjuvant kinase inhibitor therapy prior to metastasis?
In general, imatinib does not appear to cause regressions and rarely causes stable disease. Sunitinib has been reported in abstract form by Dr. Demetri to cause regressions in 3 imatinib-resistant pediatric patients.
7. As pediatric GISTs are usually wild-type for the genes for KIT and PDGFRA, what types of pathology tests and mutation analyses are needed for individual patients to guide their treatment?
Over 90% of pediatric GIST do not have PDGFRA or KIT mutations therefore I would recommend that all children ad adolescents with GIST undergo mutational testing of their tumor to better define the potential activity of imatinib.