PURPOSE: To investigate the efficacy and safety of trastuzumab deruxtecan, an antibody-drug conjugate targeting human epidermal growth factor receptor 2 (HER2) with a topoisomerase I inhibitor payload, in patients with uterine carcinosarcoma (UCS) expressing HER2. PATIENTS AND METHODS: Patients with recurrent UCS with HER2 immunohistochemistry scores ≥1+ previously treated with chemotherapy were included. Patients were assigned to the HER2-high (immunohistochemistry score ≥2+; n = 22) or low (immunohistochemistry score of 1+; n = 10) groups for primary and exploratory analyses, respectively. Trastuzumab deruxtecan 6.4 or 5.4 mg/kg was administered intravenously once every 3 weeks until unacceptable toxicity or disease progression. Dose modification was based on the updated recommended phase II dose for breast cancer to be 5.4 mg/kg. The primary end point was the objective response rate by central review in the HER2-high group. Secondary end points included the overall response rate (ORR) in the HER2-high group by investigator assessment, ORR in the HER2-low group, progression-free survival (PFS), overall survival (OS), and safety. RESULTS: The ORR by central review in the HER2-high and HER2-low groups were 54.5% (95% CI, 32.2 to 75.6) and 70.0% (95% CI, 34.8 to 93.3) and those by investigator assessments were 68.2% and 60.0%, respectively. The median PFS and OS in the HER2-high and HER2-low groups were 6.2 and 13.3 months and 6.7 months and not reached, respectively. Grade ≥ 3 adverse events occurred in 20 patients (61%). Grades 1-2 and 3 pneumonitis/interstitial lung disease occurred in eight (24%) and one (3%) patient, respectively. CONCLUSION: Trastuzumab deruxtecan has efficacy in patients with UCS, regardless of HER2 status. The safety profile was generally consistent with that previously reported. Toxicities were manageable with appropriate monitoring and treatment.

PURPOSE: Treatment options for patients with unresectable or recurrent biliary tract cancer (BTC) who progress on a gemcitabine-containing regimen are limited. In addition, the significance of anti–human epidermal growth factor receptor 2 (HER2) therapy in HER2-expressing BTC has not been sufficiently investigated. METHODS: In this phase II trial, participants from five institutions in Japan were enrolled. Eligible patients had pathologically confirmed unresectable or recurrent BTC with centrally confirmed HER2-positive (immunohistochemistry [IHC]3+ or IHC2+ and in situ hybridization [ISH]+) or HER2-low (IHC2+ and ISH–, IHC1+, and IHC0 and ISH+) and were refractory or intolerant to a gemcitabine-containing regimen. The patients received 5.4 mg/kg trastuzumab deruxtecan (T-DXd) once every 3 weeks until disease progression or unacceptable toxicity. The primary end point was the confirmed objective response rate (ORR) in HER2-positive BTC by an independent central review (threshold ORR, 15%; expected ORR, 40%). RESULTS: A total of 32 patients were enrolled and treated. Among these patients, 22 with HER2-positive disease comprised the primary efficacy population and had a confirmed ORR of 36.4% (90% CI, 19.6 to 56.1; P = .01), meeting the primary end point. Eight with HER2-low disease comprised the exploratory population and had a confirmed ORR of 12.5%. The most common ≥grade 3 treatment-related adverse events were anemia (53.1%) and neutropenia (31.3%). Eight patients (25.0%) had interstitial lung disease (ILD), including two grade 5 events. CONCLUSION: T-DXd showed promising activity in patients with HER2-positive BTC and a signal of efficacy in patients with HER2-low BTC. Although the safety profile was generally manageable, ILD requires careful monitoring and early intervention.

Background Recently, the Liver Cancer Study Group of Japan (LCSGJ) staging system for intrahepatic cholangiocarcinoma (ICC) was followed by a proposal of the American Committee on Cancer (AJCC)/International Union Against Cancer (UICC) system. The present study aimed to assess the accuracy of both systems to predict survival after curative resection for mass‐forming ICC and to establish a new staging system based on survival analysis results. The present study was conducted as a project study of the Japanese Society of Hepato‐Biliary‐Pancreatic Surgery. Methods Clinical data from 233 patients who underwent curative resection for mass‐forming ICC were retrospectively reviewed. Survival analysis was performed to identify predictors of postoperative outcomes, and a new staging system was established. The survival stratification of our proposed system was compared with two previous staging systems. Results A N0M0 cohort analysis demonstrated that tumor size, tumor number, and vascular invasion were independently associated with survival after curative resection for mass‐forming ICC, whereas serosal and periductal invasion were not. Of patients with nodal metastases, patients with T4 tumor had significantly lower overall survival rate than patients with T1, T2, or T3 tumor. Thus, we proposed a new staging system as follows: serosal invasion was excluded from the LCSGJ T categories, and patients with nodal metastases were divided into stage IVA or IVB according to T classification. The new system better stratified survival after curative resection for mass‐forming ICC than the two previous systems. Conclusions The AJCC/UICC staging system failed to stratify the Japanese patients with mass‐forming ICC. The new staging system provided better survival prediction in the patients who underwent curative resection for mass‐forming ICC, although further studies are necessary to evaluate the impact of tumor size on survival.

Background: We investigated the utility of a molecular classifier tool and genetic alterations for predicting prognosis in Japanese patients with endometrial cancer. Methods: A total of 1029 patients with endometrial cancer from two independent cohorts were classified into four molecular subtype groups. The primary and secondary endpoints were relapse-free survival (RFS) and overall survival (OS), respectively. Results: Among the 265 patients who underwent initial surgery, classified according to immunohistochemistry, patients with DNA polymerase epsilon exonuclease domain mutation had an excellent prognosis (RFS and OS), patients with no specific molecular profile (NSMP) and mismatch repair protein deficiency had an intermediate prognosis, and those with protein 53 abnormal expression (p53abn) had the worst prognosis (P < 0.001). In the NSMP group, mutant KRAS and wild-type ARID1A were associated with significantly poorer 5-year RFS (41.2%) than other genomic characteristics (P < 0.001). The distribution of the subtypes differed significantly between patients with recurrence/progression and classified by sequencing (n = 764) and patients who underwent initial surgery (P < 0.001). Among patients with recurrence/progression, 51.4% had the opportunity to receive molecular targeted therapy. Conclusions: A molecular classifier is a useful tool for determining prognosis and eligibility for molecularly targeted therapy in patients with endometrial cancer.