Marks, Randolph S.

Background: The morphologic distinction between thymic carcinomas and thymomas, specifically types B3, A, and occasionally micronodular thymomas with lymphoid stroma (MNTLS) can be challenging, as has also been shown in interobserver reproducibility studies. Since thymic carcinomas have a worse prognosis than thymomas, the diagnosis is important for patient management and treatment. This study aimed to identify a panel of immunohistochemical (IHC) markers that aid in the distinction between thymomas and thymic carcinomas in routine practice. Materials and Method: Thymic carcinomas, type A and B3 thymomas, and MNTLS were identified in an institutional database of thymic epithelial tumors (TET) (1963–2021). IHC was performed using antibodies against TdT, Glut-1, CD5, CD117, BAP1, and mTAP. Percent tumor cell staining was recorded (Glut-1, CD5, CD117); loss of expression (BAP1, mTAP) was considered if essentially all tumor cells were negative; TdT was recorded as thymocytes present or absent (including rare thymocytes). Results: 81 specimens included 44 thymomas (25 type A, 11 type B3, 8 MNTLS) and 37 thymic carcinomas (including 24 squamous cell carcinomas). Using BAP1, mTAP, CD117 (cut-off, 10%), and TdT, 88.9% of thymic carcinomas (95.7% of squamous cell carcinomas) and 77.8% of thymomas could be predicted. Glut-1 expression was not found to be useful in that distinction. All tumors that expressed CD5 in ≥50% of tumor cells also expressed CD117 in ≥10% of tumor cells. In four carcinomas with homozygous deletion of CDKN2A, mTAP expression was lost in two squamous cell carcinomas and in a subset of tumor cells of an adenocarcinoma and was preserved in a lymphoepithelial carcinoma. Conclusion: A panel of immunostains including BAP1, mTAP, CD117 (using a cut-off of 10% tumor cell expression), and TdT can be useful in the distinction between thymomas and thymic carcinomas, with only a minority of cases being inconclusive.

e20554 Background: The paradigm for locally advanced non-small cell lung cancer has been markedly altered to include maintenance durvalumab (D) post completion of definitive chemoradiation (CRT) following the publication of the Pacific trial in 2018. The toxicity of this treatment has not been well evaluated in the real-world setting. Methods: We identified 42 patients (pts) with Stage IIB-IIIC NSCLC treated at Mayo Clinic Rochester between 6/1/2018 and 10/1/2020 who received definitive CRT followed by maintenance D. Data were abstracted by retrospective chart review under an IRB approved protocol. Results: Median age was 66 yrs (range 47-90) and 62% were women. Primary lung cancer histology included 19 adenocarcinoma, 20 squamous cell, and 3 adenosquamous. The distribution of stages was: IIB (4/42), IIIA (15/42), IIIB (19/42), IIIC (4/42). Approximately half of patients had PDL1 expression > 25% (20/42). With a median follow up of 12.2 months (calculated from first cycle of D; range 4.2-30.5 months), 14 had completed one year of maintenance D, 16 were receiving ongoing D, and 10 stopped D early with 6/12 discontinuing due to disease progression (4/6 local progression, 2/6 distant progression). Other reasons for discontinuation (5/10) included grade 3 colitis, grade 2 hepatitis, aspergillus lung infection, and flare of autoimmune disorders. One quarter of patients experienced grade 2 radiation pneumonitis (RP; 10/42) with median time to development of RP 78 days from end of CRT and 45 days from start of D. RP was determined by multidisciplinary review of imaging and treatment fields. 17/42 patients developed immune related adverse events (see Table for details). There was minimal overlap between the patients who experienced pneumonitis and immune related toxicity; 2/17 had both pneumonitis and immune related toxicity (hepatitis, thyroiditis). Conclusions: In our early experience with the Pacific regimen, 29% of patients did not complete D due to either toxicity or progression during D administration. Pneumonitis was common (10/42 patients) although there were no grade 3 events. Nearly half of the patients developed an immune-related adverse event. Further analysis is needed to evaluate the real-world toxicity of this treatment as well as oncologic outcomes.[Table: see text]

Abstract Active cancer is an independent VTE risk factor (overall 6- to 9-fold increased risk) and accounts for almost 20% of all VTE in the community, but which cancer patients are at risk for VTE is largely unknown. Reportedly, VTE risk varies by tumor site, and cancer of the ovary, pancreas, colon, stomach, lung, prostate, and kidney convey particularly high VTE risk. Objective: To estimate VTE risk by tumor site. Methods: We enumerated observed cancers by tumor site for Olmsted County, MN active cancer patients with incident VTE over the seven-year period, 1991–1997 (n=152). We used 1991–1997 State Surveillance, Epidemiology, and End Results (SEER) data for Iowa to estimate the expected age-specific prevalence of cancer by tumor site in Olmsted County. VTE risk ratios (RR) for each tumor site were estimated by dividing the observed number of cancers by the expected number (calculated as the product of the SEER prevalence and the number of incident VTE cases in the age stratum). Results: For our population of 1991–1997 VTE cases, all tumor sites had RR > 5.0 (range 5.2 to 37.3, all p-values<0.05). Compared to published overall VTE odds ratios of 6–9 for active cancer compared to no cancer, the RR for some tumor sites were particularly increased. A Chi-squared test of heterogeneity of the RR across sites was highly significant (p-value<0.001). Three rare cancer sites - pancreatic cancer, lymphoma, and brain cancer - had unusually high RR (all RR>25). The high number of VTE cases with lymphoma was not due to catheter-related arm vein thrombosis. Liver, leukemia, other gastrointestinal (esophagus, small intestine, gallbladder, other biliary) and other gynecologic (primarily cervical) cancers had over twice the baseline risk (i.e., RR>17.0). On the other hand, the RR for many common cancers (breast, colorectal, ovary, lung, prostate) were essentially the same as the overall baseline risk (all had 9.5<RR<12.0). Conclusions: In contrast to previous reports, pancreas, lymphoma, brain, liver, leukemia, other gastrointestinal, and other gynecologic cancers have the highest VTE risk. Prior estimates of VTE risk by tumor site may have been biased by studies of prevalent cancers among patients hospitalized in tertiary care centers.

Abstract OBJECTIVES The aim of this study is to evaluate the efficacy of chest computed tomography (CT) to predict the pathological stage of thymic epithelial tumours (TET) using the recently introduced tumour, node and metastasis (TNM) staging with comparison to the modified Masaoka staging. METHODS Preoperative chest CT examinations in cases of resected TET with sampled lymph nodes (2006–2016) were retrospectively reviewed by 2 thoracic radiologists and radiologically (r) staged using both staging systems. A thoracic pathologist reviewed all cases for the pathological (p) stage. Concordance between r-staging and p-staging was assessed by % agreement and unweighted kappa statistics. Associations between r-stage and p-stage with outcomes were assessed using the Cox proportional hazards regression. RESULTS Sixty patients with TET were included (47 thymomas, 12 thymic carcinomas and 1 atypical carcinoid tumour). Sixteen patients (26.7%) had received neoadjuvant therapy. Fifty-four patients (90.0%) had complete resection. The overall agreement between the r-stage and p-stage was 66.7% (κ = 0.46) for TNM staging and 46.7% (κ = 0.30) for modified Masaoka staging. Agreement between r-assessment and p-assessment of the T, N and M components of the TNM stage was 61.7% (κ = 0.28), 86.7% (κ = 0.48) and 98.3% (κ = 0.88), respectively. CT overstaged 12 patients (20.0%) for TNM staging and 12 patients (20.0%) for modified Masaoka staging and understaged 8 (13.3%) and 20 (33.3%) patients for TNM staging modified Masaoka staging, respectively. The r-TNM staging accuracy was lower for patients with neoadjuvant therapy (50.0% with vs 72.7% without). During a median follow-up of 2.6 years (range 0.1–10.5 years), 12 patients had metastases and/or recurrence; 11 patients died (4 of disease). The r-TNM stage and modified Masaoka stage were associated with overall survival and progression-free survival (P < 0.001). CONCLUSIONS Preoperative chest CT is able to accurately predict p-TNM stage in two-thirds of surgically resected TET, with an agreement between radiological staging and pathological staging superior to the modified Masaoka staging.

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.

PURPOSE: Because small-cell lung cancer is a rapidly proliferating tumor, it was hypothesized that it may be more responsive to thoracic irradiation (TI) given twice-daily than once-daily. This hypothesis was tested in a phase III trial. PATIENTS AND METHODS: Patients with limited-stage small-cell lung cancer were entered onto a phase III trial, and all patients initially received three cycles of etoposide (130 mg/m 2 × 3) and cisplatin (30 mg/m 2 × 3). Subsequently, patients who did not have progression to a distant site (other than brain) were randomized to twice-daily thoracic irradiation (TDTI) versus once-daily thoracic irradiation (ODTI) given concomitantly with two additional cycles of etoposide (100 mg/m 2 × 3) and cisplatin (30 mg/m 2 × 3). The irradiation doses were TDTI, 48 Gy in 32 fractions, with a 2.5-week break after the initial 24 Gy, and ODTI, 50.4 Gy in 28 fractions. After thoracic irradiation, the patients received a sixth cycle of etoposide/cisplatin, followed by prophylactic cranial irradiation (30 Gy/15 fractions) if they had a complete response. RESULTS: Of 311 assessable patients enrolled in the trial, 262 underwent randomization to TDTI or ODTI. There were no differences between the two treatments with respect to local-only progression rates, overall progression rates, or overall survival. The patients who received TDTI had greater esophagitis (≥ grade 3) than those who received ODTI (12.3% v 5.3%; P = .05). Although patients received thoracic irradiation encompassing the postchemotherapy volumes, only seven of 90 local failures were out of the portal of irradiation. CONCLUSION: When TI is delayed until the fourth cycle of chemotherapy, TDTI does not result in improvement in local control or survival compared with ODTI.