Among these im- munologic responders, four exhibited T cells against only one neoantigen, while the others mounted T-cell responses against three to eight vaccine-encoded mutations. Data from one study participant who developed a small liver lesion fol- lowing vaccination suggest that these T cells serve an antitumor immune surveillance function. A biopsy revealed a dense infiltrate of vaccine-induced T cells, along with DNA from rare cells harboring the same TP53 mutation as the original pancreatic tumor. Because the lesion soon disappeared, the T cells presumably helped prevent nascent micrometastases from taking root. Blood samples from the vaccine- responsive individuals showed that their neoantigen-specific T cells expanded in number, eventually representing up to 10% of their circulating T cells. That amount declined during 5 months of subsequent chemotherapy, but the cell population rebounded after patients received a booster dose of autogene cevumeran. “The magnitude of the response is high—and it’s in a tumor type that historically was thought not to have such [antigenic] targets at all,” says MSKCC’s Vinod Balachandran, MD, who led the study. “When we see a high magnitude response, it strongly correlates with clinical benefit,” he adds. After a median follow-up of 18 months, none of the patients who developed vaccine-induced T-cell responses showed signs of disease recurrence, whereas patients who did not develop an immune response experienced a relapse after a median of 13.4 months following surgery. “These data continue to provide strong evidence that tumor-specific memory CD8+ T cells correlate with long-term durable remission in pancreatic cancer,” says Stephanie Dougan, PhD, of Dana-Farber Cancer Institute in Boston, MA, who was not involved in the study. “Whether boost- ing these endogenous responses with a vaccine will convert more patients into long-term survivors is worth testing in a randomized clinical trial.” BioNTech’s cofounder and CEO Uğur Şahin, MD, agrees. The first PDAC trial “was really for immunological learning,” he says. Now, the company expects to launch a phase II adjuvant trial of autogene cevumeran, with or without a checkpoint inhibitor, for the same patient population later this year. –Elie Dolgin ■ doi: 10.1158/2159-8290.CD-NB2023-0038 Women with Breast Cancer Can Attempt Pregnancy Women with hormone-responsive breast cancer can stop endocrine ther - apy to attempt pregnancy, according to findings from the POSITIVE trial (N Engl J Med 2023;388:1645–56).