Objective: To investigate the biological behavior characteristics of gastrointestinal stromal tumors (GIST) with PDGFRA mutation and the patients' survival, and elucidate the efficacy of imatinib therapy.
Methods: Patients with PDGFRA D842V and non-D842V mutations were screened from a database of 1163 patients with GIST who were treated at Peking University Cancer Hospital from 2003 to 2018. Clinicopathological data of these patients were collected, including gender, age, tumor size, mitotic phase, primary position, metastatic site, and expressions of CD117, CD34, DOG-1. The association of gene mutations with biological behavior of GIST, prognosis of patients, and efficacy of imatinib therapy was examined. Fisher's exact test was used to compare the clinical characteristics of the two groups. Kaplan-Meier method was used to analyze overall survival and recurrence-free survival.
Results: A total of 27 patients with PDGFRA mutations were screened, among whom the D842V mutation was 1.6%(19/1 163), and the rate of non-D842V mutation was 0.7%(8/1 163). There were 11 male patients and 8 female patients of D842V mutation with male to female ratio of 1.38:1 and median age of 56 (35-72) years. There were 4 male patients and 4 female patients of non-D842V mutations with male to female ratio of 1:1 and median age of 51.5 (34-82) years. The primary lesions of D824V mutation were located in stomach for 18 cases and in parenteral area for 1 case. The primary lesions of non-D842V mutation were located in stomach for 6 cases, in jejunoileum for 1 case and in colorectum for 1 case. The proportion of nuclear fission <5/50 HPF in PDGFRA mutation GIST was 17/27. Among D842V mutation patients, mitotic phase <5/50 HPF accounted for 11/19, mitotic phase >10/50 HPF accounted for 3/19, and 5-10/50 HPF accounted for 5/19. Among non-D842V mutation patients, mitotic phase <5/50 HPF accounted for 6/8, 5-10/50 HPF accounted for 2/8. Of D842V mutation patients, positive CD117 was found in 15 cases(15/19); positive DOG-1 was found in 15 cases(15/19); positive CD34 was found in 16/17 cases. Among patients with non-D842V mutation, 7 patients were positive for CD117(7/8); only 5 patients were tested for CD34, and all 5 patients were positive(5/5); only 3 patients were tested for DOG-1, and all 3 cases were positive (3/3). The 3-year recurrence-free survival rate after radical resection in D842V mutation patients was 51.9%, and that in non-D842V mutation patients was 62.5% without significant difference(P=0.380). Recurrence-free rate did not decreased in patients with D842V mutation after adjuvant imatinib treatment and the benefit rate of first-line treatment with imatinib in patients with advanced disease was zero.
Conclusions: The PDGFRA gene mutation rate is low, mostly derived from gastric GIST. D842V and non-D842V mutations present inert biological behavior. D842V mutation GIST is resistant to imatinib, and non-D842V mutation GIST can obtain benefit from imatinib treatment.