GIST is not common in AYA patients and the data on AYA GISTs are limited. In our institution, the typical adult GIST patient is male (52.9%), with mutations in KIT (53.6%) or PDGFR (4.2%), has gastric as the primary location (54.4%), and a five-year overall survival (OS) of 51%. We studied the clinical and genetic characteristics and prognoses of AYA GISTs.
All GIST patients diagnosed between the ages of 16-39 at National Cancer Centre Singapore from 1 January 2002 to 31 December 2018 were included. We retrospectively studied their clinico-molecular characteristics and outcomes.
41 AYA GIST patients were seen with a median age of 34 years old. 25 patients (61.0%) were male. 27 patients (65.9%) were Chinese. 9 (22.0%) had metastatic disease at diagnosis. The tumours were primarily in the jejunum/ileum (41.5%, n=17) or stomach (34.1%, n=14). 25 patients (61.0%) had tumor mutation testing performed. Of these, 19 (76%) had KIT and one (4%) had PDFGRA. 5 (20%) were KIT/PDGFR wildtype. Of those with KIT mutations, 17 (89.5%) were in exon 11, while 2 (10.5%) were in exon 9. The PDGFRA mutation was in exon 18. No data is available on genetic syndromes. 24 patients (58.4%) received curative-intent treatment with 3 (12.5%) subsequently had local recurrences. 14 (58.3%) received imatinib in a neoadjuvant/adjuvant setting. 17 patients (41.5%) received palliative-intent treatment with 13 (76.4%) receiving palliative imatinib. 9 (52.9%) had Sunitinib after progression. The median follow-up was 48 months (0-165). 6 patients (14.6%) had demised. Median OS for all patients was 162.0 months (95% CI: 80.8– 243.2) with no significant differences with regards to age (p=0.07), gender (p=0.91), presence of a sensitising mutation (KIT Exon 9 and 11) (p=0.26), and treatment intent (p=0.2). A significant OS difference was found between patients undergoing curative or palliative intent (162.0 vs 65.0 months, p=0.001) and in patients with different primary tumor location (p=0.029). Out of the 6 patients with uncommon primary tumor locations, 3 had demised.
AYA GISTs differ from adult GIST. In our series, 61.0% had tumor mutation analysis performed. AYA GIST also has a higher rate of small intestine primary. Further studies are needed to evaluate the low mutation and genetic testing and clinico-molecular differences to better understand how these affect outcomes.
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All authors have declared no conflicts of interest.