IDS correlates with a higher risk of the development of platinum resistance.

17556 Objectives: Primary mediastinal B-cell Lymphoma (PMBL) is recognized as a separate entity in the WHO classification. Treatment for PMBL is based on a combination of conventional dose chemotherapy, high dose chemotherapy and radiation therapy. The best strategy is still undefined. We conducted a retrospective analysis of patients with PBML to identify clinical prognostic factors. Methods: A retrospective analysis of 43 patients treated at Hospital do Cancer AC Camargo, Sao Paulo, Brazil, between 1989 and 2004. All patients had previous diagnosis of diffuse large B-cell lymphoma, with positive CD20 on neoplastic cells. A predominant anterior mediastinal lesion should be present. Induction chemotherapy regimens were grouped in first generation (CHOP/CHOP-like), third generation (PromaceCytabon/MACOP) and other (pediatric regimens, COP). Results: Age ranged from 16 to 82 years-old, 30 females and 13 male. Age < 35 yo was associated with a better prognosis (5 years OS - 56% × 34%, p = 0.048). Among clinical variables, female gender, stage IA-IIB, IPI 0–1, normal LDH, absence of mediastinal bulky disease were associated with better prognosis, although not statistically significant. Response rate to first generation regimens was: 37% CR (11/29), 24% PR (7/29) and 24% PD (7/29). Four patients were treated with Third generation regimens with 2 CR and 2 PR. 20 out of 25 patients with PR or CR to first line chemotherapy received mediastinal radiation therapy. More than 65% of patients had a follow up of 5 years or more. With a median follow up of 22.3 months, projected 5 year OS was 47% and for the responders the median PFS was 8,4 months. No difference in OS and PFS was observed among the three chemotherapy groups. Conclusion: Our analysis showed that response rate to first line regimens was around 60% and 25% of patients were primarily refractory to CHOP regimen. Age younger than 35 years old was associated with a better prognosis. 5 years overall survival was 45% and is in accordance with the literature. Although recent studies have demonstrated biological similarities between PMBL and Hodgkin’s Lymphoma, the prognosis of PMBL is less favorable than HL. Better understanding of the disease will help in developing more appropriate therapeutic strategies for PMBL. No significant financial relationships to disclose.

5576 Background: Ovarian carcinomas show homologous recombination deficiency (HRD) in up to 50% of cases and in 15 to 20% of cases occur due to germline BRCA1 or BRCA2 mutations. BRCA mutated tumors are more sensitive to PARP inhibitors and platinum based chemotherapy. The objective of this study was to characterize a cohort of ovarian cancer patients regarding HRD and to evaluate the impact of these scores in prolonged platinum sensitivity. Methods: Thirty one ovarian cancer patients with platinum resistant recurrence reexposed to platinum based chemotherapy were selected. Paraffin embedded tumor samples from 14 patients were analyzed using ONCOSCAN assay (Affymetrix) to evaluate HRD scores. The association of the scores with response rate to platinum rechallenge, overall survival and clinical pathologic factors was evaluated. Results: From the cohort of 31 patients, 15 samples from 14 patients were analyzed for genomic alterations. Median scores were 19.5 for TAI, 12.5 for cnLOH+L, 26.0 for LST and 6.3 for HRD. High scores were found in 10 out of 14 (for cnLOH+L score) and 9 out of 14 (for LST score) patients. Seven of the 14 patients analyzed analyzed for genomic alterations had response, which suggested homologous recombination deficiency. No significant differences were observed between response rates for high versus low scores. Numerically, cnLOH+L, LST and HDR scores were higher in patients with response to treatment compared to those without response. Median overall survival was 13.4 months from the beginning of platinum rechallenge and no difference in survival according to scores was observed. Among the clinical pathologic factors, family history of breast or ovarian cancer or personal history of breast cancer was associated to higher response rate to platinum rechallenge. Conclusions: In conclusion,HRD scores showed to be potential markers of response to platinum rechallenge in the platinum resistant setting. Further studies are necessary to clarify the best cutoffs for each score, the impact of tumor heterogeneity and the analysis of tumor samples in the moment of treatment. Positive family history of cancer is a clinical factor predictvie of platinum rechallenge response.

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