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A. Thomas



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    MO03 - Thymic Malignancies (ID 123)

    • Event: WCLC 2013
    • Type: Mini Oral Abstract Session
    • Track: Medical Oncology
    • Presentations: 1
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      MO03.07 - Clinical activity of sunitinib in patients with thymic carcinoma (ID 3114)

      10:30 - 12:00  |  Author(s): A. Thomas

      • Abstract
      • Presentation
      • Slides

      Background
      There are no standard treatments for patients with advanced thymic epithelial tumors (TET) in whom chemotherapy has failed. A subset of TETs over-express and harbor activating mutations of KIT. Moreover, expression of angiogenic markers correlate with invasiveness of TETs. This two-center phase II study was conducted to evaluate efficacy of sunitinib, a multi-targeted tyrosine kinase inhibitor that blocks angiogenic and other growth factors in TETs.

      Methods
      Patients with TET who had progressive disease following at least one platinum-based chemotherapy were enrolled. Sunitinib was administered orally at 50 mg once daily in 6 week cycles for 4 weeks followed by 2 weeks off until disease progression. Tumor response was assessed by computed tomography scans every 6 weeks. KIT mutations were assessed in archival tissue. Primary end-point was objective response rate in parallel cohorts (thymoma, thymic carcinoma).

      Results
      Between May 2012 and June 2013, 22 patients with thymic carcinoma [median age 58 (40-81); males 59%] and 16 with thymoma [median age 54 (31-74); males 44%] enrolled. Median of 4 (range, 1-7) and 3 (range, 1-8) cycles were administered in patients with thymic carcinoma and thymoma respectively. Among 19 evaluable patients with thymic carcinoma, there were three partial responses (16%) and 10 minor responses (50%) (Figure). Thirteen patients had stable disease (68%) and three progressive disease (16%). After median follow up of 7.8 months, the median progression-free survival was 6.2 months and 6-month survival probability 85%. In contrast, only one out of 16 patients with thymoma had a partial response (6%). Twelve patients had stable disease (75%) and three progressive disease (19%). After median follow up of 6.4 months, median progression-free survival was 5.5 months and 6-month survival probability 90.9%. Grade 3 or 4 sunitinib-related adverse events which occurred in >10% of patients included neutropenia (18%), thrombocytopenia (23%), leucopenia (18%), lymphopenia (45%), fatigue (36%), mucositis (32%) and hypertension (18%). Three patients (14%) has symptomatic decline in left ventricular ejection fraction which improved with medical management and discontinuation of sunitinib. KIT mutations were absent in tumors of 20 patients who underwent mutational analysis.Figure 1

      Conclusion
      In this phase II trial, sunitinib demonstrated anti-tumor activity unprecedented for a targeted agent in previously treated patients with thymic carcinoma. Activity was modest in thymoma. These results are intriguing as response rates of thymic carcinomas are usually lower than that for thymomas. KIT mutations did not predict responses. Ongoing exploratory analyses are evaluating biologic determinants of activity and mechanisms of resistance.

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    O22 - Mesothelioma III (ID 122)

    • Event: WCLC 2013
    • Type: Oral Abstract Session
    • Track: Mesothelioma
    • Presentations: 1
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      O22.03 - Durable cancer regressions in chemotherapy refractory mesothelioma patients with the anti-mesothelin immunotoxin SS1P and host immune depletion with pentostatin (P) and cyclophosphamide (C) (ID 1630)

      16:15 - 17:45  |  Author(s): A. Thomas

      • Abstract
      • Slides

      Background
      SS1P is a recombinant immunotoxin targeting the tumor differentiation antigen mesothelin, which is highly expressed in mesothelioma. Anti-tumor activity of SS1P was limited in phase I clinical trials due to development of neutralizing antibodies (NAbs) that limited treatment to one cycle. In immunocompetent mice P and C (P-C) can abrogate development of anti-SS1P NAbs. This pilot study was performed to determine the impact of P-C-based immune depletion on anti-SS1P NAb formation and to assess safety of P-C-SS1P.

      Methods
      Patients with progressive pleural or peritoneal mesothelioma who previously received platinum-based therapy were eligible. Up to 6 cycles of P 4 mg/m2 IV (cycle 1: days 1, 5, 9; cycle 2-6: day 1); C 200 mg PO (cycle 1: days 1-12; cycle 2-6: days 1-4) and SS1P IV (35 µg/kg, cycle 1: days 10, 12, 14; cycle 2-6: days 2, 4, 6) were administered (cycle 1 was 30 days and cycles 2-6 were 21 days) with restaging every 2 cycles in the absence of progressive disease and anti-SS1P NAbs.

      Results
      Eleven patients were enrolled. The median age was 52 years (range 43-68); male 7, female 4; pleural 9, peritoneal 2; median number of prior treatments was 3 (range 2-6). Three out of 10 evaluable patients had partial response with tumor regressions of 74%, 70% and 44% with complete resolution of metabolic activity in two patients and >70% reduction in the third (Table). The overall survival of these patients is 17+, 15+ and 18+ months. In addition, one patient with stable disease and one patient with progressive disease had dramatic response to post-SS1P chemotherapy using drugs to which they had not responded previously. All five patients who responded are alive with overall survival ranging from 11 to 18 months. The regimen of P-C delayed development of NAbs to SS1P, thereby allowing multiple cycles of therapy with SS1P. Only 2 of 10 (20%) patients developed anti-SS1P NAbs after one cycle compared to 88% of patients who received single agent SS1P in a previous study (p=0.0001), thus meeting the primary endpoint. The regimen of P-C-SS1P was safe and well tolerated and no patient developed opportunistic infections. Grade ≥ 3 adverse events were P-C related lymphopenia (100%), transaminitis (18%) and SS1P related back pain (9%), non-cardiac chest pain (18%) and fever (9%).

      Pt Overall Tumor Response[†] Delayed Tumor Response[§] Post Study Chemo. Response to Post-SS1P Chemo. Overall Survival (months)
      1 PR (-44%) Yes (7 m+) - - 18.2+
      2 PR (-74%) - - - 17.1+
      3 SD - Yes PR (-55%)* 15+
      4 PR (-70%) - - - 14.5+
      5 SD - - - 8.8
      6 PD - - - 6.2
      7 PD - - - 5.7
      8 PD Yes (4 m+)** Yes 85% decrease in tumor [18]F-FDG uptake[¶] 10.6+
      9 PD - - - 4.2
      10 SD - Yes No 7.3
      PR, partial response; SD, stable disease; PD, progressive disease; [18]F-FDG, Fluorodeoxyglucose; [†]In patients with tumor response the maximum percent decrease in tumor dimensions is shown; [§]Months from study initiation when response first observed; * PR to post-SS1P treatment with previously ineffective chemotherapy; **Patient 8 had initial PD, but at 4 months had 25% reduction in size of one of the target lesions and marked decrease of metabolic activity by PET; [¶]Patient 8 had 85% reduction in metabolic activity compared to baseline and SD by CT scan on post- SS1P chemotherapy.

      Conclusion
      SS1P and immune depletion with P-C results in significant and durable anti-tumor activity in heavily pre-treated chemotherapy refractory patients with mesothelioma.

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