Tumor grade and chemotherapy response in endometrioid endometrial cancer

The objective of this study is to evaluate the association between tumor grade and response to chemotherapy in patients with endometrioid endometrial adenocarcinoma. Patients with advanced or recurrent endometrioid endometrial adenocarcinoma of known tumor grade who received at least 3 cycles of chemotherapy were retrospectively identified at three institutions. RECIST 1.1 criteria were used to assess response to neoadjuvant, postoperative or salvage chemotherapy. Chi-square testing was used to evaluate the association between tumor grade and chemotherapy response. Ninety-one patients met inclusion criteria: 13 with grade 1, 29 with grade 2 and 49 with grade 3 tumors. Eighty-four percent of patients received chemotherapy for recurrence, 12% for postoperative residual disease, and 4% in the neoadjuvant setting. The majority (85%) received carboplatin and paclitaxel. Forty-six percent (6/13) of grade 1, 72% (21/29) of grade 2 and 43% (21/49) of grade 3 tumors achieved an objective response. Grade 2 tumors were more likely to respond to chemotherapy compared to grade 3 tumors (72% vs. 43%, p = 0.02; Table 2), and specifically more likely to respond to carboplatin/paclitaxel (72% vs. 41%, p = 0.016). Median progression-free survival for patients receiving chemotherapy for recurrence or progression was 9 months for grade 1, 8 months for grade 2, and 5 months for grade 3 tumors. Similar results between grade and treatment response were apparent in the subset of 37 patients with a recently re-assigned tumor grade (G2 88% vs. G3 44%, p = 0.032). In this series of endometrioid endometrial cancers, grade 2 tumors had the best measurable response to chemotherapy.