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e16047 Background: Management of stage I SGCC depends on pathological findings after orchiectomy. Four risk-adapted strategies were sequentially applied in a single institution during a 24-year (yr) period according to national guidelines. Here, we compare treatment burden and outcomes of each of them. Methods: From 1/1994 to 1/2018, 208 patients with stage I SGCC were prospectively included in 4 cohorts. Those without risk criteria underwent close surveillance. Patients received active treatment as follow: Group 1: 1994-1999, only patients with T > pT1 received 2 cycles of carboplatin (CBDCA AUC7 x2); Group 2: 1999-2003, patients received CBDCA AUC7 x2 if either tumor size > 4cm or rete testis invasion; Group 3 : 2004-2009, CBDCA AUC7 x2 if both tumor size > 4cm and rete testis invasion were present; Group 4 : ≥2010, CBDCA AUC7 x1 if either tumor size > 4cm or rete testis invasion. Kaplan Meier and log-rank tests were used to evaluate disease-free survival (DFS), Kruskal-Wallis test to compare amount of chemotherapy received per patient. Results: At a median follow-up of 108 months [range 3-423], 19 (9.1%) relapses had occurred. Global 3 and 5-yr DFS were 92.3% and 90%. All relapsing patients were rendered disease-free with 4 cycles of cisplatin (CDDP) - etoposide. Table 1 summarizes results by cohort: Conclusions: A risk-adapted program provided an overall specific survival of 100%. A clinically significant difference in RR was observed when 1 or 2 courses of CBDCA were given. In our series and considering treatment burden, vascular invasion was a better criteria for patient selection to adjuvant chemotherapy, showing a similar DFS but a lower no of total platinum cycles per patient.[Table: see text]

e23525 Background: Leiomyosarcomas (LMS) are soft tissue sarcomas that derive from smooth muscle cells and can arise anywhere in the body (most frequently in extremities, uterus or retroperitoneum). The clinical prognostic factors are well established but molecular factors influencing prognostic are unknown. The DMD gene, which codifies for the dystrophin protein, has been proposed as tumour suppressor gene in LMS. The aim of our study is to evaluate dystrophin expression in LMS and its relation with the patient prognosis. Methods: A total of 103 patients (pts) with LMS were analysed. Clinical and pathological data were collected retrospectively from patients’ electronic board system. Dystrophin expression was analysed by immunohistochemistry (IHC) in paraffin embedded tissue LMS samples using the Novocastra NCL-DYS2 (Leica Biosystems). Semiquantitative assessment of the staining was classified from score 0 to 3 (0 = no dystrophin expression, 1 = low expression, 2 = moderate expression, 3 = high expression). Results: Of all 103 pts, 70 (68%) had localized disease and the majority of tumours were larger than 5 cm (75%). The most frequent locations of primary LMS were extremities (n = 31; 30.1%), uterus (n = 23; 23.2%) and retroperitoneum (n = 21; 20.4%). Most LMS were high grade (G): 7 pts G1 (6.8%), 35 pts G2 (34%) 2 and 53 pts G3 (51.5%). 50 of all grade LMS (48.6%) had loss of dystrophin expression (score 0), 17 (16.5%) had score 1, 23 (22.3%) score 2 and 10 (9.7%) score 3. Loss/low dystrophin expression measured as score 0 or 1, was more frequent in grade 3 LMS compared to grade 2 or grade 1 (77.4% vs. 57.1% vs. 16.7%; p = 0.005). There were no differences in dystrophin loss between localized or metastatic disease at diagnosis (64.2% vs. 72.2%; p > 0.05). In our series, loss or reduced dystrophin expression did not correlate with the risk of relapse in localized patients or overall survival in metastatic patients. Conclusions: Loss of dystrophin expression is a common event in LMS. Loss/low dystrophin expression is more frequent in grade 3 LMS compared to grade 2 and grade 1 LMS. Loss of dystrophin expression did not correlate with risk of relapse or overall survival in our series. Additional genetic evaluations to study DMD in LMS are underway.

1582 Background: Despite the use of clinical eligibility criteria and mutation predictive models, a great proportion of families are negative for germline mutations in BRCA1/2 genes. Traditionally, risk assessment of inconclusive results included the recommendation of high-risk surveillance protocol, the update of incident cancer cases in the family and the consideration of additional testing to rule out the possibility of phenocopy. More recently, next generation sequencing multigene panels have become a standard practice in cancer genetics clinics worldwide. We addressed the value of multigene panel retesting of BRCA1/2 negative HBOC families in our institution. Methods: After genetic counseling session and informed consent, a total of 137 individuals (119 probands and 18 extra cancer-affected relatives) from distinct BRCA1/2 negative families were retested using a panel containing 11 breast and ovarian cancer susceptibility genes ( BRCA1/2, PALB2, ATM, CHEK2, PTEN, TP53, STK11, BRIP1, RAD51C, RAD51D). Results: According to the BOADICEA model, the remaining probability of mutation in BRCA1/2 or PALB2 genes in our cohort was 5.5% (0.1-61). The reasons for considering retesting were the addition of any incident cancer diagnosis in 33 cases (24%), a prior study with a low sensitivity screening technique (dHPLC) in 6 families (5%) and the expansion of the study to other putative breast and ovarian susceptibility genes in 98 families (71%). Overall, 3 pathogenic (2 BRCA2, 1 CHEK2) and 8 likely pathogenic variants (1 BRCA2, 4 CHEK2 and 3 ATM) were found. The prevalence was 8%. The detection rate among 19 families with a > 10% remaining probability of mutation in BRCA1/2 and PALB2 genes was 26%. The 3 clinically significant variants in BRCA2 were detected in 2 families and 1 updated cancer family history (BOADICEA remaining probability of 59, 61 and 12%, respectively). Cascade testing was subsequently done in 15 relatives resulting 8 in mutation carriers and 9 true negatives. Conclusions: Our results support the value of updating cancer incident cases and considering expanded panels in selected families.