Patients with early stage pancreatic ductal adenocarcinoma (PDAC) may not benefit from adjuvant therapy after surgery if the tumor is smaller than 1 cm, according to a retrospective analysis published in Cancer. Although the study indicates a change in the standard of care may be necessary for patients with particularly small tumors, additional studies are needed to validate the findings.
“The standard paradigm for the treatment of patients with potentially curable pancreatic cancer is typically surgery and then followed by chemotherapy,” David Zhen, MD, gastrointestinal medical oncologist at Seattle Cancer Care Alliance and assistant professor at the University of Washington, told Cancer Network. He was not involved in the study. “This study is interesting because, for a small group of patients that paradigm may not necessarily be true.”
To investigate the role of adjuvant therapy, study authors reviewed the National Cancer Data Base for patients with resected T1, stage 1A PDAC; that is, a diagnosis of a tumor limited to the pancreas and smaller than 2 centimeters as well as node-negative disease. All patients included in the study underwent surgery for PDAC between 2004 and 2013 and received no neoadjuvant therapy. Stratification factors included tumor size (<1 cm vs 1 to 2 cm) and choice of adjuvant therapy (no therapy, chemotherapy alone, chemotherapy and radiotherapy, or radiotherapy alone). Study authors evaluated patient demographics, tumor histology, choice of adjuvant therapy, and survival outcomes.
A total of 876 patients from the database underwent surgery for PDAC and met inclusion criteria. The cohort had a mean age at diagnosis of 66.2 years, was predominantly white (83.3%), and was evenly balanced for gender (53.1% female vs 46.9% male). Most patients had tumors between 1 and 2 cm in size (70%) and the rest had tumors smaller than 1 cm (30%). Most patients had negative surgical margins (94.2%), and nearly half had moderately differentiated tumor histology (45.9%).
Patients who received adjuvant therapy lived nearly 2 years longer than patients who did not (median overall survival [OS], 70.7 months vs 46.9 months; P = .0001). However, this survival difference disappeared when patient outcomes were stratified by tumor size.
Among patients with tumors smaller than 1 cm, no significant difference in median OS was reported between those who received adjuvant therapy and those who did not (not reached vs 85.3 months; P = .54). A multivariate analysis confirmed that this trend was independent of covariates, such as choice of adjuvant therapy, age, insurance coverage, and Charlson-Deyo score.
Dr. Zhen noted that this study raises the question about whether adjuvant therapy is necessary in the subset of patients with tumors smaller than 1 cm, but given the limitations of retrospective studies, practice may not change quite yet on the basis of this study alone. “For a lot of us, without a prospective study, it’ll be hard for us to say this is necessarily a practice changing [study], but I think it definitely raises a lot of interesting questions for future investigation,” he said.