title: Analysis of Chemopredictive Assay for Targeting Cancer Stem Cells in Glioblastoma Patients.
abstract: BACKGROUND
  The prognosis of glioblastoma (GBM) treated with standard-of-care maximal surgical resection and concurrent adjuvant temozolomide (TMZ)/radiotherapy remains very poor (less than 15 months). GBMs have been found to contain a small population of cancer stem cells (CSCs) that contribute to tumor propagation, maintenance, and treatment resistance. The highly invasive nature of high-grade gliomas and their inherent resistance to therapy lead to very high rates of recurrence. For these reasons, not all patients with similar diagnoses respond to the same chemotherapy, schedule, or dose. Administration of ineffective anticancer therapy is not only costly but more importantly burdens the patient with unnecessary toxicity and selects for the development of resistant cancer cell clones. We have developed a drug response assay (ChemoID) that identifies the most effective chemotherapy against CSCs and bulk of tumor cells from of a panel of potential treatments, offering great promise for individualized cancer management. Providing the treating physician with drug response information on a panel of approved drugs will aid in personalized therapy selections of the most effective chemotherapy for individual patients, thereby improving outcomes. A prospective study was conducted evaluating the use of the ChemoID drug response assay in GBM patients treated with standard of care.
  
  
  METHODS
  Forty-one GBM patients (mean age 54 years, 59% male), all eligible for a surgical biopsy, were enrolled in an Institutional Review Board-approved protocol, and fresh tissue samples were collected for drug sensitivity testing. Patients were all treated with standard-of-care TMZ plus radiation with or without maximal surgery, depending on the status of the disease. Patients were prospectively monitored for tumor response, time to recurrence, progression-free survival (PFS), and overall survival (OS). Odds ratio (OR) associations of 12-month recurrence, PFS, and OS outcomes were estimated for CSC, bulk tumor, and combined assay responses for the standard-of-care TMZ treatment; sensitivities/specificities, areas under the curve (AUCs), and risk reclassification components were examined.
  
  
  RESULTS
  Median follow-up was 8 months (range 3-49 months). For every 5% increase in in vitro CSC cell kill by TMZ, 12-month patient response (nonrecurrence of cancer) increased two-fold, OR=2.2 (P=.016). Similar but somewhat less supported associations with the bulk tumor test were seen, OR=2.75 (P=.07) for each 5% bulk tumor cell kill by TMZ. Combining CSC and bulk tumor assay results in a single model yielded a statistically supported CSC association, OR=2.36 (P=.036), but a much attenuated remaining bulk tumor association, OR=1.46 (P=.472). AUCs and [sensitivity/specificity] at optimal outpoints (>40% CSC cell kill and >55% bulk tumor cell kill) were AUC=0.989 [sensitivity=100/specificity=97], 0.972 [100/89], and 0.989 [100/97] for the CSC only, bulk tumor only, and combined models, respectively. Risk categorization of patients was improved by 11% when using the CSC test in conjunction with the bulk test (risk reclassification nonevent net reclassification improvement [NRI] and overall NRI=0.111, P=.030). Median recurrence time was 20 months for patients with a positive (>40% cell kill) CSC test versus only 3 months for those with a negative CSC test, whereas median recurrence time was 13 months versus 4 months for patients with a positive (>55% cell kill) bulk test versus negative. Similar favorable results for the CSC test were observed for PFS and OS outcomes. Panel results across 14 potential other treatments indicated that 34/41 (83%) potentially more optimal alternative therapies may have been chosen using CSC results, whereas 27/41 (66%) alternative therapies may have been chosen using bulk tumor results.
  
  
  CONCLUSIONS
  The ChemoID CSC drug response assay has the potential to increase the accuracy of bulk tumor assays to help guide individualized chemotherapy choices. GBM cancer recurrence may occur quickly if the CSC test has a low in vitro cell kill rate even if the bulk tumor test cell kill rate is high.
authors.affiliation: Department of Radiology, University of Mississippi Medical Center, Jackson, MS 39216.
authors.forename: Candace M
authors.initials: CM
authors.lastname: Howard
authors.affiliation: Department of Biological Sciences, Marshall University, Huntington, WV 25755.
authors.forename: Jagan
authors.initials: J
authors.lastname: Valluri
authors.affiliation: Department of Neuroscience, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25705.
authors.forename: Anthony
authors.initials: A
authors.lastname: Alberico
authors.affiliation: Department of Neuroscience, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25705.
authors.forename: Terrence
authors.initials: T
authors.lastname: Julien
authors.affiliation: Department of Neuroscience, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25705.
authors.forename: Rida
authors.initials: R
authors.lastname: Mazagri
authors.affiliation: Department of Neuroscience, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25705.
authors.forename: Robert
authors.initials: R
authors.lastname: Marsh
authors.affiliation: Department of Neuroscience, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25705.
authors.forename: Hoyt
authors.initials: H
authors.lastname: Alastair
authors.affiliation: Department of Medicine and Surgery, University of Salerno, Italy.
authors.forename: Antonio
authors.initials: A
authors.lastname: Cortese
authors.affiliation: Department of Data Science, University of Mississippi Medical Center, Jackson, MS 39216.
authors.forename: Michael
authors.initials: M
authors.lastname: Griswold
authors.affiliation: Department of Data Science, University of Mississippi Medical Center, Jackson, MS 39216.
authors.forename: Wanmei
authors.initials: W
authors.lastname: Wang
authors.affiliation: Department of Anatomy and Pathology, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25705.
authors.forename: Krista
authors.initials: K
authors.lastname: Denning
authors.affiliation: Department of Anatomy and Pathology, Joan C. Edwards School of Medicine, Marshall University, Huntington, WV 25705.
authors.forename: Linda
authors.initials: L
authors.lastname: Brown
authors.affiliation: Department of BioMolecular Sciences, National Center for Natural Products Research, University of Mississippi, University, MS; Department of Radiation Oncology, University of Mississippi Medical Center Cancer Institute, Jackson, MS 39216. Electronic address: pclaudio@olemiss.edu.
authors.forename: Pier Paolo
authors.initials: PP
authors.lastname: Claudio