Paludo, Jonas

SummaryThe management of Waldenström macroglobulinaemia (WM) relies predominantly on small trials, one of which has demonstrated activity of dexamethasone, rituximab and cyclophosphamide (DRC) in the frontline setting. We report on the efficacy of DRC, focusing on relapsed/refractory (R/R) patients. Ibrutinib, a recently approved agent in WM demonstrated limited activity in patients with MYD88WT genotype. Herein, we additionally report on the activity of DRC based on the MYD88L265P mutation status. Of 100 WM patients evaluated between January 2007 and December 2014 who received DRC, 50 had R/R WM. The overall response rate (ORR) was 87%. The median progression‐free survival (PFS) and time‐to‐next‐therapy (TTNT) were 32 (95% confidence interval [CI]: 15–51) and 50 (95% CI: 35–60) months, respectively. In the previously untreated cohort (n = 50), the ORR was 96%, and the median PFS and TTNT were 34 months (95% CI: 23–not reached [NR]) and NR (95% CI: 37–NR), respectively. Twenty‐five (86%) of 29 genotyped patients harbored MYD88L265P. The response rates and outcomes were independent of MYD88 mutation status. Grade ≥3 adverse effects included neutropenia (20%), thrombocytopenia (7%) and infections (3%). Similar to the frontline setting, DRC is an effective and well‐tolerated salvage regimen for WM. In contrast to ibrutinib, DRC offers a less expensive, fixed‐duration option, with preliminary data suggesting efficacy independent of the patients’ MYD88 status.

Key Points PVD is an active combination in relapsed lenalidomide-refractory MM patients. PVD with weekly bortezomib offers a simpler, more convenient, and well-tolerated regimen option.

Objectives: Extraskeletal osteosarcoma (EO) is a malignant neoplasm that produces osteoid, bone, and chondroid material without direct attachment to bone or periosteum. Surgical resection is the mainstay of treatment; the role of chemotherapy is not well defined. Therefore, we evaluated the impact of chemotherapy in the survival of patients with EO. Methods: All EO patients seen at Mayo Clinic between 1990 and 2014 were assessed. Forty-three patients were included after all archived pathology slides were reviewed to confirm the diagnosis of EO. Results: Of 43 patients, 37 patients had localized disease and 6 patients had metastatic disease at diagnosis. Chemotherapy was used in 73% and 75% of patients, respectively. Chemotherapy was predominantly anthracycline based, and included platinum in 22 patients (84%). Median overall survival (OS) and progression-free survival (PFS) were 50 months (95% confidence interval, 25-99), and 21 months (95% confidence interval, 13-not reached), respectively. There was a trend towards longer OS and PFS in patients who received chemotherapy. Those who received platinum-based therapy had remarkably prolonged OS (median, 182 vs. 18 mo; 5-year, 61% vs. 0%; P=0.01) and PFS (median, not reached vs. 10 mo; 5-year, 56% vs. 0%; P=0.005). Baseline characteristics were similar in the platinum and nonplatinum group. In patients who received chemotherapy, relapse/recurrence rate was lower in the platinum-based group (41%) as opposed to the nonplatinum-based group (100%; P=0.02). In the neoadjuvant setting, the overall response rate of platinum-containing regimens was 27%. Conclusions: Our results suggest a clinical benefit when platinum-based chemotherapy is incorporated in the management of patients with EO. We plan to validate this further with an expanded multicenter analysis.

714 Background: Mismatch repair deficient (dMMR) colorectal cancer (CRC) has been shown to be responsive to blockade with anti-programmed death-1 (PD-1) antibodies. We describe a cohort of 17 patients with dMMR mCRC receiving treatment with pembrolizumab. Methods: Patients were identified through review of the Mayo Clinic electronic medical record (EMR) and chemotherapy administration records from May 2015 through September 2016. All patients with dMMR mCRC who received treatment with pembrolizumab were included. The EMR was reviewed to identify demographic, clinical, pathologic and treatment details. Overall survival (OS), progression free survival (PFS) and disease control rate (DCR=CR+PR+SD) are reported. Time to event analysis was calculated using the Kaplan-Meier method. Results: A total of 17 patients were included in this analysis; median age at diagnosis was 48.5 years (range 25-93); 59% were female. Most primary tumors were right sided (n=12; 71%), 4 (24%) were left sided and 1 (5%) was a tumor of unknown primary within the bowel. Thirteen (75%) patients received 2 or more lines of therapy prior to pembrolizumab (range 1-4). All patients received 2 mg/kg every 3 weeks, with the exception of two patients on a clinical trial; one who received 200 mg every 3 weeks, the other received 10 mg/kg every 2 weeks. The most common mutations (mut) identified were loss of MLH1 (9/12) and PMS2 (10/12), 4 patients had germline mut. KRAS mut was identified in 6/15 patients and only 1 patient had BRAF mut. Number of cycles of pembrolizumab ranged from 1 to 35, with 10 (59%) patients receiving 6 or more cycles. DCR at first assessment was 57%, with 7% CR and 50% PR. Median follow-up was 28 months (95% CI 18-55). Median OS was 103 months (95% CI NR-NR); 12-month OS was 88% and 24-month OS was 81%. Median OS post-PD-1 therapy was NR (95% CI 2-NR). Median PFS was 19 months (95% CI 5-19); 12-month PFS was 64% and 24-month PFS was 0%. At time of analysis, 11 patients remain on PD-1 therapy; 4 patients have died. Conclusions: Anti-PD1 blockade with pembrolizumab can provide long lasting benefit in dMMR mCRC, even in heavily pretreated patients.