title: Tumor marker CA-125 as an evaluator and response indicator in ovarian cancer: its quantitative correlation with tumor volume.
abstract: BACKGROUND
  The tumor marker Cancer Antigen 125 (CA 125), though not ovarian cancer specific, is widely used for the evaluation of suspected and under-treated ovarian cancer. Many studies show that serum CA 125 level demonstrates ovarian tumor burden and its response, but they lack quantitative correlation between the two. Instead, they rely on clinical or radiological assessment of gross tumor burden. This study examines ovarian tumor volumes and corresponding serum CA 125 values before and during chemotherapy.
  
  
  METHODS
  [corrected] Ovarian tumor volume was measured by CT scans at pre-chemotherapy and after each cycle of chemotherapy in 15 patients. Blood serum CA 125 was determined on the days of CT scans using a one-step immunoenzymatic assay.
  
  
  RESULTS
  There was no statistically significant correlation (r = 0.18, p > 0.05) between ovarian tumor volumes and CA 125 among patients at pre-chemotherapy or any subsequent time. In individual patients, the reduction or increase in tumor volume correlated with the corresponding CA 125 values during chemotherapy in 85% (12 out of 14) of patients. Mean CA 125 halving time was 44.1 days, which correlated with tumor halving time (r = 0.63, p < 0.05).
  
  
  CONCLUSIONS
  Values of CA 125 cannot be used for comparison of ovarian tumor mass among patients. However, serial estimation of CA 125 in individuals is fairly reliable in terms of the course of the tumor. CT scan is a more informative response indicator, but it is costly and hence may be supplemented by the easy and economical CA 125 estimation.
authors.affiliation: Medical Physics Unit, Institute Rotary Cancer Hospital, All India Institute of Medical Sciences, New Delhi, India. drpratikkumar@hotmail.com
authors.forename: Pratik
authors.initials: P
authors.lastname: Kumar
authors.forename: Madan Mohan
authors.initials: MM
authors.lastname: Rehani
authors.forename: Lalit
authors.initials: L
authors.lastname: Kumar
authors.forename: Raju
authors.initials: R
authors.lastname: Sharma
authors.forename: Neerja
authors.initials: N
authors.lastname: Bhatla
authors.forename: Rama
authors.initials: R
authors.lastname: Chaudhry
authors.forename: Sanjay
authors.initials: S
authors.lastname: Thulkar
authors.forename: K Ramaiyer
authors.initials: KR
authors.lastname: Sundaram
authors.forename: Neeta
authors.initials: N
authors.lastname: Kumar
mesh_terms: D018394:CA-125 Antigen / Q000097:blood*; D005260:Female; D006801:Humans; D009367:Neoplasm Staging; D010051:Ovarian Neoplasms / Q000097:blood* / Q000175:diagnosis / Q000188:drug therapy / Q000473:pathology*; D013997:Time Factors; D015898:Tomography Scanners, X-Ray Computed; D016896:Treatment Outcome
chemical_list: D018394:CA-125 Antigen