'Time accrued' may help set conditional survival after tumor resection

Last Updated: 2015-02-18

By Will Boggs MD

NEW YORK (Reuters Health) - Disease-free survival improves with increasing time following resection of gastrointestinal stromal tumors (GIST), according to a retrospective cohort study.

"As patients live longer and come back to clinic one or two years after surgery and want to know what is my prognosis 'now,' conditional survival is able to give patients information on this question, as it takes into account 'time accrued' beyond the static factors that were associated with the cancer when it was first resected," Dr. Timothy M. Pawlik, from The Johns Hopkins University, Baltimore, Maryland, told Reuters Health by email.

Conditional disease-free survival (DFS), which estimates the probability that a patient will continue to remain disease free after a given length of DFS, has been proposed as a more accurate way to predict prognosis in patients who have survived for a period following surgery.

Dr. Pawlik's team assessed the comparative performance of established GIST risk stratification and prognostic scoring systems and characterized conditional DFS in 502 patients who underwent curative-intent surgical resection of a primary GIST.

Overall DFS after resection of primary GISTs was 95% at one year, 83% at three years, and 74% at five years, according to the February 11 JAMA Surgery online report.

Factors associated with decreased DFS included older age, male sex, tumor size greater than 10 cm, tumor originating in the small bowel or rectum, mitotic rate greater than 10 mitoses per 50 high-power fields, and no treatment with adjuvant tyrosine kinase inhibitors.

The Memorial Sloan Kettering Cancer Center (MSKCC) GIST nomogram best predicted overall DFS, whereas the American Joint Committee on Cancer (AJCC) system had the best discrimination for gastric tumors. The modified National Institutes of Health (NIH) criteria, MSKCC GIST nomogram, and AJCC system had equivalent discriminatory ability for nongastric tumors.

The three-year DFS of 83% decreased to 74% at six years, but patients who remained disease-free at three years had a conditional DFS of 89% three years later. Similarly, the conditional three-year disease free survival at five years was 92%, compared with an actuarial DFS of 68%.

Differences between actuarial DFS and conditional DFS were smaller in patients predicted to have better outcomes and were more pronounced for patients with higher risk of recurrence.

"Physicians need to be aware of the concept of conditional survival," Dr. Pawlik said. "Providers need to know that survival is dynamic and goes beyond static tumor-specific factors collected at the time of diagnosis/surgery. Conditional survival is important for many cancers. In particular, conditional survival is important for those cancers with a traditionally high mortality rate. We have another paper on conditional survival for a different type of cancer (cholangiocarcinoma) coming out in the next couple months in JAMA Surgery."

Dr. Ajay V. Maker, from the University of Illinois at Chicago, wrote an invited commentary related to this report. He told Reuters Health by email, "Conditional DFS is a metric that provides information not traditionally published or known for most cancers that helps to individualize prognosis for each patient as time elapses. It allows us to personalize the conversation we have with our patients regarding expectations for the future. Furthermore, it may help us personalize surveillance plans and strategies for patients that could decrease costly and time-consuming physician visits, tests, scans, and/or adjuvant treatments."

"With each passing year of disease-free survival, patients with the 'best' biology of disease will remain without recurrence, and these patients will therefore show the greatest difference in predicted and actuarial DFS," Dr. Maker said. "In the future, perhaps we can use conditional DFS to identify additional risk factors of recurrence, and to identify patients for individualized surveillance plans, trials, and adjuvant treatment strategies."

The Royal College of Physicians and Surgeons of Canada partially funded this research. The authors made no disclosures.

SOURCE: http://bit.ly/1Agy003 and http://bit.ly/1zo7GLu

JAMA Surg 2015.