Jon D. Weingart

Detection of Circulating Tumor DNA in Early- and Late-Stage Human Malignancies

Circulating tumor DNA can be used in a variety of clinical and investigational settings across tumor types and stages for screening, diagnosis, and identifying mutations responsible for therapeutic response and drug resistance. Circulating Tumor DNA for Early Detection and Managing Resistance Cancer evolves over time, without any warning signs. Similarly, the development of resistance to therapy generally becomes apparent only when there are obvious signs of tumor growth, at which point the patient may have lost valuable time. Although a repeat biopsy may be able to identify drug-resistant mutations before the tumor has a chance to regrow, it is usually not feasible to do many repeat biopsies. Now, two studies are demonstrating the utility of monitoring the patients’ blood for tumor DNA to detect cancer at the earliest stages of growth or resistance. In one study, Bettegowda and coauthors showed that sampling a patient’s blood may be sufficient to yield information about the tumor’s genetic makeup, even for many early-stage cancers, without a need for an invasive procedure to collect tumor tissue, such as surgery or endoscopy. The authors demonstrated the presence of circulating DNA from many types of tumors that had not yet metastasized or released detectable cells into the circulation. They could detect more than 50% of patients across 14 tumor types at the earliest stages, when these cancers may still be curable, suggesting that a blood draw could be a viable screening approach to detecting most cancers. They also showed that in patients with colorectal cancer, the information derived from circulating tumor DNA could be used to determine the optimal course of treatment and identify resistance to epidermal growth factor receptor (EGFR) blockade. Meanwhile, Misale and colleagues illustrated a way to use this information to overcome treatment resistance. These authors also found that mutations associated with EGFR inhibitor resistance could be detected in the blood of patients with colorectal cancer. In addition, they demonstrated that adding MEK inhibitors, another class of anticancer drugs, can successfully overcome resistance when given in conjunction with the EGFR inhibitors. Thus, the studies from Bettegowda and Misale and their colleagues show the effectiveness of analyzing circulating DNA from a variety of tumors and highlight the potential investigational and clinical applications of this novel technology for early detection, monitoring resistance, and devising treatment plans to overcome resistance. The development of noninvasive methods to detect and monitor tumors continues to be a major challenge in oncology. We used digital polymerase chain reaction–based technologies to evaluate the ability of circulating tumor DNA (ctDNA) to detect tumors in 640 patients with various cancer types. We found that ctDNA was detectable in >75% of patients with advanced pancreatic, ovarian, colorectal, bladder, gastroesophageal, breast, melanoma, hepatocellular, and head and neck cancers, but in less than 50% of primary brain, renal, prostate, or thyroid cancers. In patients with localized tumors, ctDNA was detected in 73, 57, 48, and 50% of patients with colorectal cancer, gastroesophageal cancer, pancreatic cancer, and breast adenocarcinoma, respectively. ctDNA was often present in patients without detectable circulating tumor cells, suggesting that these two biomarkers are distinct entities. In a separate panel of 206 patients with metastatic colorectal cancers, we showed that the sensitivity of ctDNA for detection of clinically relevant KRAS gene mutations was 87.2% and its specificity was 99.2%. Finally, we assessed whether ctDNA could provide clues into the mechanisms underlying resistance to epidermal growth factor receptor blockade in 24 patients who objectively responded to therapy but subsequently relapsed. Twenty-three (96%) of these patients developed one or more mutations in genes involved in the mitogen-activated protein kinase pathway. Together, these data suggest that ctDNA is a broadly applicable, sensitive, and specific biomarker that can be used for a variety of clinical and research purposes in patients with multiple different types of cancer.

Extent of surgical resection is independently associated with survival in patients with hemispheric infiltrating low-grade gliomas

OBJECTIVEIt remains unknown whether the extent of surgical resection affects survival or disease progression in patients with supratentorial low-grade gliomas. METHODSWe conducted a retrospective cohort study (n = 170) between 1996 and 2007 at a single institution to determine whether increasing extent of surgical resection was associated with improved progression-free survival (PFS) and overall survival (OS). Surgical resection of gliomas defined as gross total resection (GTR) (complete resection of the preoperative fluid-attenuated inversion recovery signal abnormality), near total resection (NTR) (<3-mm thin residual fluid-attenuated inversion recovery signal abnormality around the rim of the resection cavity only), or subtotal resection (STR) (residual nodular fluid-attenuated inversion recovery signal abnormality) based on magnetic resonance imaging performed less than 48 hours after surgery. Our main outcome measures were OS, PFS, and malignant degeneration-free survival (conversion to high-grade glioma). RESULTSOne hundred thirty-two primary and 38 revision resections were performed for low-grade astrocytomas (n = 93) or oligodendrogliomas (n = 77). GTR, NTR, and STR were achieved in 65 (38%), 39 (23%), and 66 (39%) cases, respectively. GTR versus STR was independently associated with increased OS (hazard ratio, 0.36; 95% confidence interval, 0.16–0.84; P = 0.017) and PFS (HR, 0.56; 95% confidence interval, 0.32–0.98; P = 0.043) and a trend of increased malignant degeneration-free survival (hazard ratio, 0.46; 95% confidence interval, 0.20–1.03; P = 0.060). NTR versus STR was not independently associated with improved OS, PFS, or malignant degeneration-free survival. Five-year OS after GTR, NTR, and STR was 95, 80, 70%, respectively, and 10-year OS was 76, 57, and 49%, respectively. After GTR, NTR, and STR, median time to tumor progression was 7.0, 4.0, and 3.5 years, respectively. Median time to malignant degeneration after GTR, NTR, and STR was 12.5, 5.8, and 7 years, respectively. CONCLUSIONGTR was associated with a delay in tumor progression and malignant degeneration as well as improved OS independent of age, degree of disability, histological subtype, or revision versus primary resection. GTR should be safely attempted when not limited by eloquent cortex.

Phase I Trial of Temozolomide Plus O6-Benzylguanine for Patients With Recurrent or Progressive Malignant Glioma

PURPOSE We conducted a two-phase clinical trial in patients with progressive malignant glioma (MG). The first phase of this trial was designed to determine the dose of O6-BG effective in producing complete depletion of tumor AGT activity for 48 hours. The second phase of the trial was designed to define the maximum tolerated dose (MTD) of a single dose of temozolomide when combined with O6-BG. In addition, plasma concentrations of O6-BG and O6-benzyl-8-oxoguanine were evaluated after O6-BG. PATIENTS AND METHODS For our first phase of the clinical trial, patients were scheduled to undergo craniotomy for AGT determination after receiving a 1-hour O6-BG infusion at 120 mg/m2 followed by a continuous infusion at an initial dose of 30 mg/m2/d for 48 hours. The dose of the continuous infusion of O6-BG escalated until tumor AGT was depleted. Once the O6-BG dose was established a separate group of patients was enrolled in the second phase of clinical trial, in which temozolomide, administered as a single dose at the end of the 1-hour O6-BG infusion, was escalated until the MTD was determined. RESULTS The O6-BG dose found to be effective in depleting tumor AGT activity at 48 hours was an IV bolus of 120 mg/m2 over 1 hour followed by a continuous infusion of 30 mg/m2/d for 48 hours. On enrolling 38 patients in six dose levels of temozolomide, the MTD was established at 472 mg/m2 with dose-limiting toxicities limited to myelosuppression. CONCLUSION This study provides the foundation for a phase II trial of O6-BG plus temozolomide in temozolomide-resistant MG.

Identification of der(1;19)(q10;p10) in five oligodendrogliomas suggests mechanism of concurrent 1p and 19q loss.

Deletions of portions of chromosomes 1p and 19q are closely associated with the oligodendroglioma histologic phenotype. In most cases, 1p and 19q are codeleted, yet the mechanism of dual loss is unexplained. We report 5 cases (World Health Organization grade III) in which metaphase cytogenetics identified a derivative chromosome consisting of what appears to be the whole arms of 1q and 19p forming a der(1;19)(q10;p10). Metaphase fluorescent in situ hybridization (FISH) confirmed the derivative chromosome was composed of 1q and 19p material in 3 cases; in 2 cases with few metaphases, FISH confirmed 19p material on the derivative chromosome. In all cases, interphase FISH showed net loss of 1p and 19q in 77% to 92% of cells, and microsatellite studies were consistent with 1p and 19q loss. We hypothesize the following: occurrence of a balanced whole-arm translocation between chromosomes 1 and 19 forming 2 derivative chromosomes, one composed of 1q and 19p, the other of 1p and 19q. Subsequent loss of the der(1;19)(p10;q10) then results in the simultaneous 1p and 19q loss observed in oligodendroglioma with retention of the der(1;19)(q10;p10) seen in these cases.

Association of surgically acquired motor and language deficits on overall survival after resection of glioblastoma multiforme

OBJECTIVEBalancing the benefits of extensive tumor resection with the consequence of potential postoperative deficits remains a challenge in malignant astrocytoma surgery. Although studies have suggested that increasing extent of resection may benefit survival, the effect of new postoperative deficits on survival remains unclear. We set out to determine whether new-onset postoperative motor or speech deficits were associated with survival in our institutional experience with glioblastoma multiforme (GBM). METHODSWe retrospectively reviewed records of all patients (age range, 18–70 years; Karnofsky Performance Scale score, 80–100) who had undergone GBM resection between 1996 and 2006 at a single institution. Survival was compared between patients who had experienced surgically acquired motor or language deficits versus those who did not experience these deficits. RESULTSThree hundred six consecutive patients (age, 54 ± 11 years; median Karnofsky Performance Scale score, 80) underwent primary GBM resection. Nineteen patients (6%) developed surgically acquired motor deficits and 15 (5%) developed surgically acquired language deficits. Median survival was decreased in patients who acquired language deficits (9.6 months; P < 0.05) or motor deficits (9.0 months; P < 0.05) versus patients without surgically acquired deficits (12.8 months). Two-year survival was 8% and 0% for patients with surgically acquired motor or language deficits, respectively, versus 23% for patients without new-onset deficits. CONCLUSIONIn our experience, the development of new perioperative motor or language deficits was associated with decreased overall survival despite similar extent of resection and adjuvant therapy. Although it is well known that surgically induced neurological deficits affect quality of life, our results suggest that these surgical morbidities may also affect survival. Care should be taken to avoid surgically induced deficits in the management of GBM.

Poor drug distribution as a possible explanation for the results of the PRECISE trial

OBJECT Convection-enhanced delivery (CED) is a novel intracerebral drug delivery technique with considerable promise for delivering therapeutic agents throughout the CNS. Despite this promise, Phase III clinical trials employing CED have failed to meet clinical end points. Although this may be due to inactive agents or a failure to rigorously validate drug targets, the authors have previously demonstrated that catheter positioning plays a major role in drug distribution using this technique. The purpose of the present work was to retrospectively analyze the expected drug distribution based on catheter positioning data available from the CED arm of the PRECISE trial. METHODS Data on catheter positioning from all patients randomized to the CED arm of the PRECISE trial were available for analyses. BrainLAB iPlan Flow software was used to estimate the expected drug distribution. RESULTS Only 49.8% of catheters met all positioning criteria. Still, catheter positioning score (hazard ratio 0.93, p = 0.043) and the number of optimally positioned catheters (hazard ratio 0.72, p = 0.038) had a significant effect on progression-free survival. Estimated coverage of relevant target volumes was low, however, with only 20.1% of the 2-cm penumbra surrounding the resection cavity covered on average. Although tumor location and resection cavity volume had no effect on coverage volume, estimations of drug delivery to relevant target volumes did correlate well with catheter score (p < 0.003), and optimally positioned catheters had larger coverage volumes (p < 0.002). Only overall survival (p = 0.006) was higher for investigators considered experienced after adjusting for patient age and Karnofsky Performance Scale score. CONCLUSIONS The potential efficacy of drugs delivered by CED may be severely constrained by ineffective delivery in many patients. Routine use of software algorithms and alternative catheter designs and infusion parameters may improve the efficacy of drugs delivered by CED.

Establishing percent resection and residual volume thresholds affecting survival and recurrence for patients with newly diagnosed intracranial glioblastoma

INTRODUCTION Surgery is first-line therapy for glioblastoma, and there is evidence that gross total resection is associated with improved survival. Gross total resection, however, is not always possible, and relationships among extent (percent) of resection (EOR), residual volume (RV), and survival are unknown. The goals were to evaluate whether there is an association between EOR and RV with survival and recurrence and to establish minimum EOR and maximum RV thresholds. METHODS Adult patients who underwent primary glioblastoma surgery from 2007 to 2011 were retrospectively reviewed. Three-dimensional volumetric tumor measurements were made. Multivariate proportional hazards regression analysis was used to evaluate the relationship between EOR and RV with survival and recurrence. RESULTS Of 259 patients, 203 (78%) died and 156 (60%) had tumor recurrence. The median survival and progression-free survival were 13.4 and 8.9 months, respectively. The median (interquartile range) pre- and postoperative tumor volumes were 32.2 (14.0-56.3) and 2.1 (0.0-7.9) cm(3), respectively. EOR was independently associated with survival (hazard ratio [HR], 0.995; 95% confidence interval [CI]: 0.990-0.998; P = .008) and recurrence (HR [95% CI], 0.992 [0.983-0.998], P = .005). The minimum EOR threshold for survival (P = .0006) and recurrence (P = .005) was 70%. RV was also associated with survival (HR [95% CI], 1.019 [1.006-1.030], P = .004) and recurrence (HR [95% CI], 1.024 [1.001-1.044], P = .03). The maximum RV threshold for survival (P = .01) and recurrence (P = .01) was 5 cm(3). CONCLUSION This study shows for the first time that both EOR and RV are significantly associated with survival and recurrence, where the thresholds are 70% and 5 cm(3), respectively. These findings may help guide surgical and adjuvant therapies aimed at optimizing outcomes for glioblastoma patients.

A clinicopathologic reappraisal of brain stem tumor classification: Identification of pilocytic astrocytoma and fibrillary astrocytoma as distinct entities

Brain stem tumors in children have been classified pathologically as low grade or high grade gliomas and descriptively as diffuse gliomas, intrinsic gliomas, midbrain tumors, tectal gliomas, pencil gliomas, dorsal exophytic brain stem tumors, pontine gliomas, focal medullary tumors, cervicomedullary tumors, focal gliomas, or cystic gliomas.

Recent advances in brain tumor therapy: local intracerebral drug delivery by polymers.

New approaches to malignant glioma are being actively investigated. Local drug delivery directly to the site of the tumor is one novel approach that has been approved by the US FDA and other regulatory agencies worldwide. This agent, Gliadel®, delivers the chemotherapeutic drug carmustine (BCNU) from a biodegradable polymer placed in the resection cavity after brain tumor surgery. Gliadel® represents the first clinical application of polymer delivery for brain tumors, but the potential for this new methodology is far greater. In this review, we will briefly summarize the development of Gliadel® from a laboratory idea to its current role as an approved treatment for gliomas. Then we will present the most recent work being done to expand the potential benefits of polymeric delivery for brain tumors. This work includes trials for its use as the initial therapy for gliomas, as well as its use against metastasis. Further clinical trials exploring the maximum-tolerated dose and the combination of Gliadel® with systemic chemotherapeutic treatments such as temozolamide and O6–benzylguanine will be reviewed. Finally, we will present preclinical work on the efficacy of polymeric methods for delivering other chemotherapeutic agents, and a variety of novel compounds that modify brain tumor biology. This latter work represents potential future clinical applications of local polymeric drug delivery to the brain and other sites where cancers can occur.

Outcome analysis of childhood low-grade astrocytomas.

We aimed to determine the long‐term natural history of low‐grade astrocytomas (LGA) in children, with respect to pathology, and to evaluate influence of treatment on survival.