Neo-adjuvant (NA) Imatinib for gastrointestinal stromal tumours (GISTs): What is the optimal length of treatment?

Date 28 September 2019
Event ESMO 2019 Congress
Session Poster Display session 1
Topics GIST
Sarcoma
Presenter Tom Wilson
Citation Annals of Oncology (2019) 30 (suppl_5): v683-v709. 10.1093/annonc/mdz283
Authors T. Wilson1, H. Lyons1, H. Winter1, T. Bird1, S. Falk1, S. Gangadhara2
  • 1Oncology Department, University Hospitals Bristol NHS Trust - Bristol Haematology and Oncology Centre, BS2 8ED - Bristol/GB
  • 2Oncology, Royal United Hospitals Bath NHS Foundation trust, BA1 3NG - Bath/GB

Abstract

Background

GISTs are rare tumours with an incidence of around 1/100000/year. The principle treatment in localised disease remains resection. If an R0 resection is not expected, Imatinib can be used in the NA setting to shrink tumours and improve chances of a complete resection. Current guidelines suggest Imatinib should be used for 6-12 months in the NA setting.

Methods

Data were collected for patients treated for GISTs with Imatinib in either the NA or palliative (PA) setting in two UK tertiary centres to assess response in the primary tumour volume (PTV). This study aimed to find the time to maximum reduction of PTV in NA and PA settings.

Results

29 patients were treated with Imatinib over a 3 year period; 13 in the PA setting and 16 in the NA setting. In the NA setting, 10 patients proceeded to surgery, 2 patients declined surgery and 4 patients remained inoperable. All patients deemed operable at baseline underwent surgery after NA Imatinib. The median time to surgery was 7.2mths (Range (R) 1.6 – 28.9mths). Overall, 10 patients died (none in the NA setting), 5 on treatment and 5 post-treatment. At baseline, the median PTV was 199.3cm3 (R 4.0 – 10472.0cm3). The median time to best response was 7.6mths (R 1.4 – 46.2mths) for all patients, 4.7mths (R 1.4 – 21.6mths) in NA patients and 14.1mths (R 3.3 – 46.2mths) in PA patients. As the majority of NA patients did not have progressive disease (PD) prior to surgery, the maximum response may not have been reached and therefore the results in PA patients may better reflect the time to best response. 9 patients had PD, 2 in NA setting with 1 patient proceeding to surgery. The median time to PD for all patients was 19.6mths (R 1 – 51.4mts). The overall response rate to Imatinib was 85.2%. The median reduction in PTV was 65.3% (R -182.7 – 93.4%). In NA patients the median reduction in PTV was 62.7% (R -182.7 – 93.4%) and in PA patients the median reduction in PTV was 57.6% (R 20 – 82.4%).

Conclusions

Imatinib has high response rates in both the NA and PA settings. This study suggests the maximum reduction in PTV can be achieved after greater than 12mths of treatment. For patients responding to NA Imatinib who have ongoing concerns regarding resectability, a more prolonged course of treatment may further reduce PTV to facilitate an R0 resection.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Sharath Gangadhara.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.