Abstract P3-13-01: Application of supine MRI-based 3D printing breast surgical guide for precision breast-conserving surgery

Background

If the size of the tumor is large, neoadjuvant systemic therapy (NST) is performed to reduce the size of the tumor and to conserve the breast. It is known that magnetic resonance imaging is more accurate than mammography (MMG) or ultrasonography (USG) in determining the area of residual cancer in breast-conserving surgery (BSG) after NST. However, there are some problems when performing BCS using MRI. Because the posture of MRI test is different from the posture at surgery, it is difficult to accurately mark the area of the tumor observed in MRI. Neoadjuvant systemic therapy reduces tumor size and often makes it difficult to detect the original tumor area on preoperative MRI. Even if the tumor is not visible in the image, the cancer cells may remain, so it is important to accurately indicate the extent of the initial tumor and remove it. Until now, however, there has been no way to accurately mark past breast tumors in the breast. We have developed a breast surgical guide (BSG) that can mark a range of tumor directly on the breast using three-dimensional printing technology based on supine MRI. This study analyzed the results of patients who underwent BCS using a 3D printing breast surgical guide (3D-BSG) based on supine MRI.

Methods

This trial was designed as a prospective single-institution cohort study. Our study protocol was approved by the Institutional Review Board of Asan Medical Center, Seoul, Korea (IRB No. 2016-1237). Patients who were expected to undergo BCS after NST were enrolled in this study and supine MRI was performed before and after NST. From MRI images, morphological shapes of breasts and tumors were modeled. The prepared digital model was saved in stereolithography file format and then exported to a 3D printer. 3D-BSG is designed to be able to mark the skin and attach the dye injecting column to mark the around the tumor. The breast tissue was removed with blue dye on the basis of the border. To obtain tumor free margin, intraoperative frozen sections were identified in several cavities and re-excision was performed if tumor positive.

Results

Between January 2016 and May 2017, 50 patients were enrolled in the study. BCS was applied to 40 patients, except for those who were rejected or mastectomy. Complete remission was observed in 15 patients after NST. Four patients had tumor positive on resection margins on frozen biopsy during operation, two with IDC and two with DCIS. Re-excision was performed in these patients and tumor negative margin was confirmed in all patients in the final pathology results. The median size of the long axis of the tumor was 1.7 cm (range, 0.5 to 4.5 cm) and the median size of the long axis of the removed breast tissue was 5.1 cm (range, 2.3 to 8.1 cm). The distance between tumor and resection margin was 1.2 cm (range, 0.1 to 4.8 cm)..

Conclusions

In BCS, the application of the supine MRI based 3D-BSG showed low rates of positive margins. Unlike conventional localization techniques, application of 3D-BSG does not cause pain to the patient, has no radiation exposure, and has no time required for the localization procedure, so it will be helpful for patients in BCS in the future.

Citation Format: Ko B, Kim N, Seo J, Kim H, Gong G, Kim S, Son B, Ahn SH. Application of supine MRI-based 3D printing breast surgical guide for precision breast-conserving surgery [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P3-13-01.

Abstract P6-17-03: 24 months results from a double-blind, randomized phase III trial comparing the efficacy and safety of neoadjuvant then adjuvant trastuzumab and its biosimilar candidate CT-P6 in HER2 positive early breast cancer (EBC)

Background CT-P6 is a proposed biosimilar to reference trastuzumab (RTZ). A double-blind, randomized, phase III trial showed similar efficacy and safety for CT-P6 and RTZ in HER2 positive EBC (NCT02162667). The primary endpoint, pathological complete response rate was within the predefined margin to demonstrate similarity (Lancet Oncol 2017). Safety and efficacy at 1 year (ESMO 2017), and cardiac toxicity at a median of 19 months (SABCS 2017) were similar between the two treatment groups. Here we report updated disease-free survival (DFS), overall survival (OS) and cardiac toxicity data with a median follow-up of 2 years.

Methods A total of 549 patients with HER2 positive EBC were randomized to receive CT-P6 (n=271) or RTZ (n=278) in combination with docetaxel (Cycles 1-4) and 5-fluorouracil, epirubicin and cyclophosphamide (Cycles 5-8). CT-P6 or RTZ was administered at 8 mg/kg (Cycle 1 only) followed by 6 mg/kg every 3 weeks. After surgery, patients received CT-P6 or RTZ monotherapy then entered the follow-up period up to 3 year of last patient enrollment. Time to event analyses were performed using Cox regression and Kaplan-Meier methods.

Results A total of 528 patients (259/271 in CT-P6 and 269/278 in RTZ) entered the follow-up period after completing therapy. The median follow-up duration was over 27 months. The number of DFS events (32 [12.4%] in CT-P6 and 26 [10.0%] in RTZ) and OS events (14 [5.2%] in CT-P6 and 12 [4.3%] in RTZ) were comparable in the ITT set. Additionally, DFS and OS were similar between CT-P6 group and RTZ group in both the per-protocol set (PPS) and the ITT set. In the ITT set, the proportion of 2-year DFS (95% CI) was 86% (80% – 90%) in CT-P6 and 90% (85% – 93%) in RTZ. The proportion of 2-year OS was 97% (93% – 98%) in CT-P6 and 98% (96% – 99%) in RTZ. Median DFS and OS have not been reached. After 1-year treatment, no new cases of heart failure were reported during the follow-up period. Left ventricular ejection fraction (LVEF) was similar in both groups (mean LVEF, more than 60%).

Table 1.Summary of Long Term Efficacy Endpoints PPSITT set CT-P6 (n=248)Reference Trastuzumab (n=256)CT-P6 (n=258)Reference Trastuzumab (n=261)Proportion of DFS1 year (95% CI)0.95 (0.91 – 0.97)0.96 (0.93 – 0.98)0.95 (0.91 – 0.97)0.96 (0.93 – 0.98)2 years (95% CI)0.86 (0.80 – 0.90)0.90 (0.85 – 0.93)0.86 (0.80 – 0.90)0.90 (0.85 – 0.93)p-value0.33240.3085 CT-P6 (n=248)Reference Trastuzumab (n=256)CT-P6 (n=271)Reference Trastuzumab (n=278)Proportion of OS1 year (95% CI)1.00 (1.00 – 1.00)1.00 (0.97 – 1.00)0.99 (0.97 – 1.00)0.99 (0.97 – 1.00)2 year (95% CI)0.97 (0.94 – 0.99)0.98 (0.96 – 0.99)0.97 (0.93 – 0.98)0.98 (0.96 – 0.99)3 year (95% CI)0.94 (0.88 – 0.97)0.93 (0.86 – 0.96)0.92 (0.86 – 0.96)0.93 (0.87 – 0.96)p-value0.93290.5057

Conclusions The efficacy and cardiac toxicity profile between CT-P6 and RTZ in EBC patients were consistent with published data. Time to event analyses as secondary efficacy endpoints supported the similarity for the two study drugs. CT-P6 was consistently well tolerated with a similar cardiotoxicity profile to that of RTZ through long duration of follow-up.

Citation Format: Esteva FJ, Lee S, Yu S, Kim M, Kim N, Stebbing J. 24 months results from a double-blind, randomized phase III trial comparing the efficacy and safety of neoadjuvant then adjuvant trastuzumab and its biosimilar candidate CT-P6 in HER2 positive early breast cancer (EBC) [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P6-17-03.

Guidelines for DNA recombination and repair studies: Cellular assays of DNA repair pathways

Understanding the plasticity of genomes has been greatly aided by assays for recombination, repair and mutagenesis. These assays have been developed in microbial systems that provide the advantages of genetic and molecular reporters that can readily be manipulated. Cellular assays comprise genetic, molecular, and cytological reporters. The assays are powerful tools but each comes with its particular advantages and limitations. Here the most commonly used assays are reviewed, discussed, and presented as the guidelines for future studies.

Predictive value of a fragmented QRS complex in diagnosing patients with myocardial ischemia

Background

A fragmented QRS complex (fQRS) is caused by conduction abnormalities of the ventricle secondary to myocardial ischemia and/or scar in patients with myocardial infarction. However, the implications of the fQRS in the development of coronary artery disease with myocardial ischemia in those without a scar remain unknown.

Methods

We studied electrocardiograms (ECGs) obtained from 150 patients (60.5 ± 8.5 years, 102 men) with myocardial ischemia, which was confirmed by performing both, a nuclear exercise stress test and coronary angiography. We also studied ECGs obtained from 601 patients (58.5 ± 10.0 years, 315 men) who showed a negative nuclear exercise stress test (control group). Patients in whom the nuclear exercise stress test showed a myocardial scar were excluded.

Results

An fQRS was more commonly observed in patients with myocardial ischemia (n = 48, 32.0%) than in the control group (n = 133, 22.1%) (P = 0.011). The sensitivity, specificity, positive, and negative predictive values of fQRS in diagnosing myocardial ischemia were 32.0, 77.9, 26.5, and 82.1%, respectively. The fQRS (odds ratio 1.580, 95% confidence interval 1.020‐2.446, P = 0.040) was an independent predictor of myocardial ischemia after adjusting for age, sex, current smoking habits, ST‐T changes on ECG, as well as histories of hypertension, diabetes, and dyslipidemia. Moreover, the fQRS showed an incremental prognostic value over conventional risk factors (χ² = 5, P = 0.032) and over a combination of conventional factors and ST‐T changes (χ² = 9, P = 0.014).

Conclusions

The fQRS is a moderately sensitive and independent predictor of myocardial ischemia.

Unscheduled DNA synthesis leads to elevated uracil residues at highly transcribed genomic loci in Saccharomyces cerevisiae

Recombination and mutagenesis are elevated by active transcription. The correlation between transcription and genome instability is largely explained by the topological and structural changes in DNA and the associated physical obstacles generated by the transcription machinery. However, such explanation does not directly account for the unique types of mutations originating from the non-canonical residues, uracil or ribonucleotide, which are also elevated at highly transcribed regions. Based on the previous findings that abasic (AP) lesions derived from the uracil residues incorporated into DNA in place of thymine constitute a major component of the transcription-associated mutations in yeast, we formed the hypothesis that DNA synthesis ensuing from the repair of the transcription-induced DNA damage provide the opportunity for uracil-incorporation. In support of this hypothesis, we show here the positive correlation between the level of transcription and the density of uracil residues in the yeast genome indirectly through the mutations generated by the glycosylase that excise undamaged cytosine as well as uracil. The higher uracil-density at actively transcribed regions is confirmed by the long-amplicon PCR analysis. We also show that the uracil-associated mutations at a highly transcribed region are elevated by the induced DNA damage and reduced by the overexpression of a dUTP-catalyzing enzyme Dut1 in G1- or G2-phases of the cell cycle. Overall, our results show that the DNA composition can be modified to include higher uracil-content through the non-replicative, repair-associated DNA synthesis.

Uracil in DNA, a major source of spontaneous mutations, can occur through the deamination of cytosine residues or through the direct incorporation of dUTP by DNA polymerases. Recent studies in yeast have shown that the uracil-associated mutations occur more frequently at highly transcribed regions. Because the reduction in dUTP pool decreased these mutations, it was postulated that the extent of uracil-incorporation into DNA is significantly affected by the local transcription activity. We show here that the higher transcription rate does correlate with the higher uracil-density in the yeast genome. We further provide multiple lines of evidence supporting a model of uracil-incorporation into DNA that is dependent on the repair synthesis of transcription-associated DNA damage.

The G-quadruplex DNA stabilizing drug pyridostatin promotes DNA damage and downregulates transcription of Brca1 in neurons

The G-quadruplex is a non-canonical DNA secondary structure formed by four DNA strands containing multiple runs of guanines. G-quadruplexes play important roles in DNA recombination, replication, telomere maintenance, and regulation of transcription. Small molecules that stabilize the G-quadruplexes alter gene expression in cancer cells. Here, we hypothesized that the G-quadruplexes regulate transcription in neurons. We discovered that pyridostatin, a small molecule that specifically stabilizes G-quadruplex DNA complexes, induced neurotoxicity and promoted the formation of DNA double–strand breaks (DSBs) in cultured neurons. We also found that pyridostatin downregulated transcription of the Brca1 gene, a gene that is critical for DSB repair. Importantly, in an in vitro gel shift assay, we discovered that an antibody specific to the G-quadruplex structure binds to a synthetic oligonucleotide, which corresponds to the first putative G-quadruplex in the Brca1 gene promoter. Our results suggest that the G-quadruplex complexes regulate transcription in neurons. Studying the G-quadruplexes could represent a new avenue for neurodegeneration and brain aging research.