Gastrointestinal stromal tumor: optimizing the use of cross-sectional chest imaging during follow-up.

PURPOSE: To identify the frequency of and variables associated with thoracic metastasis in patients with gastrointestinal stromal tumor (GIST) to help optimize the use of cross-sectional chest imaging.

MATERIALS AND METHODS: This retrospective institutional review board-approved study included 631 patients (343 men; mean age, 55 years; range, 19-94 years) with pathologically confirmed GIST who were identified with a natural language processing algorithm in a review of radiologic reports from January 2004 through October 2012, followed by manual confirmation. The requirement for informed consent was waived. Available imaging, pathologic, and clinical records were reviewed to confirm the presence of abdominal and thoracic metastases. The association of age; sex; size, location, mitotic count, and risk stratification of the primary tumor; initial treatment; presence of abdominal metastases; and bulky abdominal metastases (more than 10 lesions larger than 1 cm, or more than five lesions with at least one larger than 5 cm) with development of thoracic metastases, the primary outcome measure, was studied by using logistic regression.

RESULTS: During median follow-up of 61.4 months (interquartile range, 37.8-93 months), 401 of 631 (63.5%) patients developed metastatic disease (median interval, 6.9 months; interquartile range, 0-25.6 months), all with peritoneal (n = 324) and/or hepatic metastases (n = 303). Bulky abdominal metastases were found in 218 (34.5%) patients. Although 579 (91.8%) patients underwent chest imaging, only 64 of 631 (10.1%) developed thoracic metastases (median, 51.4 months; interquartile range, 36-78.7 months); all had bulky abdominal metastases except one patient who presented with symptomatic scapular metastasis. Only bulky abdominal metastasis was significantly associated with the development of thoracic metastasis (P < .0001; odds ratio, 42.6; range, 8.6-211.5).

CONCLUSION: Thoracic metastases are relatively uncommon in patients with GIST and are significantly associated only with presence of bulky abdominal metastases.