The percentage of patients receiving a mutational test was highest for patients living in Europe where 26 of 27 (96.3%) patients reported having a test with other continents varying from 66.7% (South America) to 81.8% (Asia).
The patient population in this survey was biased toward proactive patients in two ways. Patients participating in the registry are self-referred/more proactive and patients participating in the survey are further selected for proactive participation. As a result, the percentage of patients reporting having a mutational test in this survey was higher (80% n = 237) than in the LRG registry (57% of living patients) and much higher than in the general GIST population15, which was 26.7% of patients diagnosed between 2010-2015 in a report of 3888 GIST patients from the Surveillance, Epidemiology, and End Results (SEER) database15.
Treatments and Mutational Testing
Patients reported receiving their GIST diagnosis more often in a “large hospital or academic institution (teaching hospital with an affiliated medical university” (n = 162, 55%) compared to a “local hospital (small-medium sized hospital” (n = 105, 36%) or a “private local doctor/physician or non-hospital based diagnostic center” (n = 28, 9%) (Table 1).
In the Mutational Testing sub-section of the survey (Table 2), patients were asked “What is the name of the institution where your doctor practices?” There were 21 institutions listed by three or more patients comprising a total of 115 patients. The most frequently listed sites were: Memorial Sloan Kettering, Dana Farber, Oregon Health Sciences University, MD Anderson, Sylvester Comprehensive Cancer Center and Red de Salud Christus UC (Chile). These more popular sites had a slightly higher percentage of mutational testing (101 of 115, 88%) compared to sites with two or less patients, with 123 of 160 having a mutational test (77%) and were slightly more likely to explain mutational testing results, 76% versus 69% in the less frequently cited centers.
However, there was considerable crossover between larger centers and smaller centers within the treatment and testing centers (questions 22, 25, and 26 from Supplemental Table 1). Many patients maintained a relationship with both a local doctor and a GIST/Sarcoma specialty center, in some cases with more than one expert center. When combined with the low percentage of patients in this survey that did not receive a mutational test, it makes any attempt to correlate mutational testing frequency with center size or GIST expertise difficult.
One of the major findings of this survey was that from a patient’s perspective, there were three major reasons why a mutational test was performed in their case: Their doctor ordered/suggested the test (54% n = 129), the LRG advised/suggested the test (25% n = 60) and the patient asked their doctor for the test (22% n = 52). In many cases, more than one of these reasons were selected (Supplemental Table 1-Question 19, Figure 2).
Patients with no mutational testing (Supplemental Table 1-Question 27, Figure 3) were asked, “Why was mutational testing not done in your case?” The most common two responses were, “My doctor never mentioned it as part of my treatment” (34%) and “I do not know” (29%). Other reasons included, “Mutational testing did not apply in my case (i.e., low risk, metastatic) (17%), “Not enough tissue” (9%), “Cost/insurance” (9%) and “My doctor mentioned it but said that I did not need it” (7%).
Treatment Changes Based on Mutational Testing
One of the most important findings in this study was that for 58 of the patients (24.5%), treatment was changed based on the results of the mutational test (Supplemental Table 1-question 20, Figure 4A). These treatment changes included (Figure 4B), stopped treatment (n = 14, 24%), switched treatment (n = 10, 17%), increased dosage of current treatment (n = 6, 10%) and other (n = 28, 48%). A post hoc analysis of the free text answers from the 28 “Other” responses (Figure 4C) found that treatment was started for 7 patients (25%) after test confirmed results, 7 patients (25%) declined TKI treatment due to mutation type, 6 patients (21%) switched treatment, two patients stopped treatment, two opted for TKI versus surgery, two opted for surgery versus TKI, one patient’s treatment did not change and one patient’s diagnosis was changed from GIST to a different sarcoma (also changing treatment).