Physicians could more accurately test patients with colon cancer for Lynch syndrome by using a single tumor sequencing test instead of the current protocol of up to six sequential tests, a new study suggests. The process may also be faster in some cases.

“We found that up-front tumor testing is actually more sensitive and more specific for detecting Lynch syndrome than the old, multiple-test model,” study coauthor Rachel Pearlman, MS, a genetic counselor at Ohio State University Wexner Medical Center, said in an interview. “Tumor sequencing resulted in a 10% improvement in Lynch syndrome detection rates while also providing important information about treatment options for the patients.”

According to Ms. Pearlman, screening for Lynch syndrome is recommended for all patients with colon cancer and can require multiple sequential tests. It affects an estimated 3% of these patients, putting them at higher risk of several kinds of cancers including endometrial, ovarian, and gastric.

“Identifying the condition at the time of diagnosis can potentially impact treatment options and also help to facilitate intensive surveillance for other types of cancer,” Ms. Pearlman said. “In addition, we’ll know that the patients’ family members are at risk and will benefit from genetic counseling and testing.”

However, “traditional sequential testing is complex and confusing to patients and clinicians and occurs over a prolonged period, incurring risk for loss to follow-up,” the investigators wrote in JAMA Oncology .

For the new study, the researchers sought to confirm whether tumor sequencing, a form of genetic testing, would be faster and more accurate than the current sequential testing approach.

In a multicenter study, they prospectively tested tumor DNA in 2015 and 2016. They also tested another 46 patients who had been previously confirmed to have Lynch syndrome.

The average age of the patients was 60 years, 52% were women, 89% were white. Hispanics and Asians made up just 1% each of the total. Most of the cancers were stage II (26%) or stage III (40%).

Tumor sequencing identified all of the 46 confirmed cases of Lynch syndrome and turned up 12 more in the larger group, the researchers found.

Sensitivity of tumor sequencing was better (100%; 95% confidence interval, 93.8%-100%) than immunohistochemical testing plus BRAF (89.7%; 95% CI, 78.8%-96.1%; P = .04) and microsatellite instability testing plus BRAF (91.4%; 95% CI, 81.0%-97.1%; P = .07), and its specificity was equal to the other approaches, Ms. Pearlman and her associates reported.

Researchers also reported that tumor sequencing identified nearly 300 cases of tumors with genetic mutations that could impact therapy.

Eesults from tumor sequencing are available in a median of 2 weeks, which may be longer than some other tests, but “it requires less time overall by eliminating multiple follow-up tests in a subset of cases,” the study authors wrote.

“While this new test is currently more expensive than traditional step-wise testing, it will eliminate many other tests for a subset of patients so that it may be more cost-effective overall. If it is not now, it will certainly be in the future as the costs of tumor sequencing continue to decline,” Ms. Pearlman said. “However, formal cost-analysis studies will be necessary to determine if this is a cost-effective approach.”

The study was funded by a grant from Pelotonia, an annual cycling event that supports cancer research, and the National Cancer Institute. Myriad Genetics donated the sequence testing used for some patients.

SOURCE: Hampel H et al. JAMA Oncol. 2018 Mar 29. doi: 10.1001/jamaoncol.2018.0104 .


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