The GIST Risk Calculator is based on research from Dr. Heikki Joensuu, Professor of Oncology at the University of Helsinki and the Research Director at the Helsinki Comprehensive Cancer Center, and his colleagues. The study drew from an international sample of 2000 diagnosed GIST patients, and was analyzed using a mathematical model designed by Professor Aki Vehtari of Aalto University. Dr. Joensuu is one of the most respected researchers in the world of GIST.
The digital calculator estimates risk of recurrence of the disease if left without treatment other than surgical intervention for a primary tumor with no metastases based on tumor size, mitotic count, tumor site and rupture. Professor Vehtari stated, “The nonlinear mathematic model predicts the combined effect of the main prognostic factors more accurately than any known model before. However, it is important to note that the historical data is solely comprised of patients that were treated via surgery alone, and that the new targeted therapy drugs have reduced risk of recurrence. The prognostic contour maps resulting from nonlinear modeling have been widely accepted by doctors, but the digital calculator significantly improves the usability of the maps.”
According to Heikki Joensuu, “Providing the patient with a reliable estimation of recurrence is faster with the digital calculator. Expensive drugs that can also have side effects can thus be targeted to the high risk patients who are not likely to be cured by surgery alone. The risk estimation should be examined together with the patient in order to guarantee that the patient understands the reasons behind treatment decisions.”
This is a somewhat unique tool in that it presents data over a time series (i.e. your chance of survival and non-recurrence after t years.) The values reflect both survival and non-recurrence. This is different from the already existing models, including the NIH, Modified NIH and AFIP models. The data can be helpful when determining the timing of follow up scans.
The inclusion of tumor rupture as a factor is an important addition to the calculations. The calculator also includes e-GISTS, which have a higher risk for recurrence. This may, however, be due to the fact that e-GISTS may actually be metastases from an unidentified primary tumor in the gastrointestinal tract (Joensuu H, Vehtari A, Rihimaki J, et al. Risk of gastrointestinal stromal tumor recurrence after surgery: an analysis based on pooled population-based cohorts. Lancet Oncology 201;13(3); 265-274.)
It also includes a continuous scale for both mitotic rate and tumor size.
Due to the large population-based sample, the nomogram may be a more ‘real world” predictor of recurrence, but the differences in the various tools may have the potential to cause some confusion when utilized by the layman. It is important to recognize that the tool was designed to be used by cancer care and research professionals, and should be used as part of a conversation with your medical team.
Patients with a calculated high risk of recurrence are usually directed to treatment with adjuvant imatinib, but whether or not an individual with an intermediate risk is offered adjuvant treatment remains somewhat controversial.
The calculator is available online for all cancer care and medical professionals.