PET Scans Helped Tailor Induction Chemotherapy for Esophageal Cancers

Using positron emission tomography (PET) scans during induction chemotherapy for esophageal cancer, researchers were able to assess patient response to treatment and adjust their therapy, leading to an improved rate of pathologic complete response prior to surgery.

These phase II data (abstract 1) from CALGB 80803 were presented by Karyn A. Goodman, MD, a radiation oncologist at the University of Colorado School of Medicine, at a press conference ahead of the 2017 American Society of Clinical Oncology (ASCO) Gastrointestinal Cancers Symposium, held January 19–21 in San Francisco.

“CALGB 80803 shows the benefit of a new paradigm of using metabolic imaging in esophageal and gastroesophageal junction cancer to individualize multimodality therapy and improve outcomes in this poor prognosis population,” Goodman said during the press conference. “Early response assessment using PET imaging can be incorporated into future studies to identify more effective new regimens for esophageal and gastroesophageal junction cancers.”

According to Goodman, patients with stage II/III esophageal and gastroesophageal junction cancers usually receive about 5 weeks of chemoradiation prior to undergoing surgery. Even with this aggressive approach, the 5-year survival is only between 40% to 50%. Although several chemoradiation regimens are available, there are currently few data on which approach will be effective in individual patients.

With this study, Goodman and colleagues wanted to use an interim PET scan after initiation of induction therapy to determine if the patient’s tumor was responding to treatment. The study included 257 patients with resectable esophageal and gastroesophageal junction adenocarcinomas. All patients had a baseline PET and were then randomly assigned to induction chemotherapy with either modified FOLFOX-6 or carboplatin/paclitaxel. Patients underwent a repeat PET scan between days 36 to 42.

Those patients who were non-responders (35% or less decrease in standardized uptake value) were crossed over to the alternative treatment arm plus concurrent radiotherapy. Patients who were responders continued on the same arm with the addition of concurrent radiotherapy. Thirty-nine of 129 patients assigned FOLFOX and 49 of 128 patients assigned carboplatin/paclitaxel crossed over to the other treatment arm. Surgical resection took place 6 weeks after therapy completion. The primary endpoint of the study was an improvement in pathologic complete response from an expected rate of 5% to 20% by changing therapy.

Overall, the rate of pathologic complete response was 18% among PET non-responders: 19% among PET non-responders who switched from FOLFOX to carboplatin/paclitaxel and 17% among PET non-responders who switched from carboplatin/paclitaxel to FOLFOX. According to Goodman, prior studies have shown a response rate of about 5% among patients with tumors that did not respond to induction chemotherapy.

The rate of pathologic complete response among PET responders was 26%, and for all patients it was 22.7%.

According to Goodman, several previous studies that looked at patients who received preoperative chemoradiation showed that those patients who achieved pathologic complete response at the time of surgery had better overall and disease-free survival.

“We know [pathologic complete response] is a prognostic marker and, in addition, we will be getting the additional information in terms of patient survival in this study in the next 6 months or so,” she said.  

Commenting on the results, conference moderator and ASCO Expert Nancy Baxter, MD, PhD, said, “This really helps move the field forward in terms of finding personalized ways of better treating our patients, particularly those who are responding poorly to the therapy we initially offered them and to people who have been diagnosed with these very hard to treat cancers.”