title: Thymidylate synthase expression and outcome of patients receiving pemetrexed for advanced nonsquamous non-small-cell lung cancer in a prospective blinded assessment phase II clinical trial.
abstract: BACKGROUND
  In retrospective analyses of patients with nonsquamous non-small-cell lung cancer treated with pemetrexed, low thymidylate synthase (TS) expression is associated with better clinical outcomes. This phase II study explored this association prospectively at the protein and mRNA-expression level.
  
  
  METHODS
  Treatment-naive patients with nonsquamous non-small-cell lung cancer (stage IIIB/IV) had four cycles of first-line chemotherapy with pemetrexed/cisplatin. Nonprogressing patients continued on pemetrexed maintenance until progression or maximum tolerability. TS expression (nucleus/cytoplasm/total) was assessed in diagnostic tissue samples by immunohistochemistry (IHC; H-scores), and quantitative reverse-transcriptase polymerase chain reaction. Cox regression was used to assess the association between H-scores and progression-free/overall survival (PFS/OS) distribution estimated by the Kaplan-Meier method. Maximal χ² analysis identified optimal cutpoints between low TS- and high TS-expression groups, yielding maximal associations with PFS/OS.
  
  
  RESULTS
  The study enrolled 70 patients; of these 43 (61.4%) started maintenance treatment. In 60 patients with valid H-scores, median (m) PFS was 5.5 (95% confidence interval [CI], 3.9-6.9) months, mOS was 9.6 (95% CI, 7.3-15.7) months. Higher nuclear TS expression was significantly associated with shorter PFS and OS (primary analysis IHC, PFS: p < 0.0001; hazard ratio per 1-unit increase: 1.015; 95%CI, 1.008-1.021). At the optimal cutpoint of nuclear H-score (70), mPFS in the low TS- versus high TS-expression groups was 7.1 (5.7-8.3) versus 2.6 (1.3-4.1) months (p = 0.0015; hazard ratio = 0.28; 95%CI, 0.16-0.52; n = 40/20). Trends were similar for cytoplasm H-scores, quantitative reverse-transcriptase polymerase chain reaction and other clinical endpoints (OS, response, and disease control).
  
  
  CONCLUSIONS
  The primary endpoint was met; low TS expression was associated with longer PFS. Further randomized studies are needed to explore nuclear TS IHC expression as a potential biomarker of clinical outcomes for pemetrexed treatment in larger patient cohorts.
authors.affiliation: Thoracic Oncology, Aberdeen Royal Infirmary, University of Aberdeen, Aberdeen, United Kingdom. mnicolson@nhs.net
authors.forename: Marianne C
authors.initials: MC
authors.lastname: Nicolson
authors.forename: Dean A
authors.initials: DA
authors.lastname: Fennell
authors.forename: David
authors.initials: D
authors.lastname: Ferry
authors.forename: Kenneth
authors.initials: K
authors.lastname: O'Byrne
authors.forename: Riyaz
authors.initials: R
authors.lastname: Shah
authors.forename: Vanessa
authors.initials: V
authors.lastname: Potter
authors.forename: Geraldine
authors.initials: G
authors.lastname: Skailes
authors.forename: Sunil
authors.initials: S
authors.lastname: Upadhyay
authors.forename: Paul
authors.initials: P
authors.lastname: Taylor
authors.forename: Valerie
authors.initials: V
authors.lastname: André
authors.forename: Tuan S
authors.initials: TS
authors.lastname: Nguyen
authors.forename: Scott P
authors.initials: SP
authors.lastname: Myrand
authors.forename: Carla
authors.initials: C
authors.lastname: Visseren-Grul
authors.forename: Mayukh
authors.initials: M
authors.lastname: Das
authors.forename: Keith M
authors.initials: KM
authors.lastname: Kerr
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000201:enzymology / Q000401:mortality* / Q000473:pathology; D000328:Adult; D000368:Aged; D000971:Antineoplastic Combined Chemotherapy Protocols / Q000627:therapeutic use*; D002289:Carcinoma, Non-Small-Cell Lung / Q000188:drug therapy / Q000201:enzymology / Q000401:mortality* / Q000473:pathology; D002945:Cisplatin / Q000008:administration & dosage; D005260:Female; D005500:Follow-Up Studies; D005971:Glutamates / Q000008:administration & dosage; D006147:Guanine / Q000008:administration & dosage / Q000031:analogs & derivatives; D006801:Humans; D007124:Immunoenzyme Techniques; D008175:Lung Neoplasms / Q000188:drug therapy / Q000201:enzymology / Q000401:mortality* / Q000473:pathology; D008297:Male; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000188:drug therapy / Q000201:enzymology / Q000401:mortality* / Q000473:pathology; D009367:Neoplasm Staging; D000068437:Pemetrexed; D011379:Prognosis; D011446:Prospective Studies; D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015996:Survival Rate; D013940:Thymidylate Synthase / Q000235:genetics / Q000378:metabolism*
chemical_list: D005971:Glutamates; D012333:RNA, Messenger; D000068437:Pemetrexed; D006147:Guanine; D013940:Thymidylate Synthase; D002945:Cisplatin