Poster Presentation Clinical Oncology Society of Australia Annual Scientific Meeting 2018

Is serum CA15-3 useful for assessing disease progression during systemic therapy in patients with metastatic breast cancer (MBC)? (#353)

Parameswar R Rachumalla 1 , Joseph Descallar 2 , Abhijit Pal 1 , Brooke E Wilson 1 , Wei Xuan 2 , Belinda E Kiely 3 , Kelly Mok 1 , Eugene Moylan 1 , Bavanthi Balakrishnar 1 , Diana Adams 3 , Sandra Harvey 4 , Michelle Harrison 1 , Annette Tognela 3 , Ray Asghari 4 , Stephen DellaFiorentina 3 , Paul De Souza 1 5 , MeiLing Yap 6 , Karen Lim 6 , Geoff Delaney 6 , George Papadatos 7 , Miriam Boxer 6 8 , Shalini Vinod 6 , Clara Inkyung Lee 4 9 10
  1. Medical Oncology, Liverpool Cancer Therapy Centre,Liverpool Hospital, Liverpool, NSW, Australia
  2. Biostatistics, Ingham Institute, Liverpool, NSW, Australia
  3. Medical Oncology, Macarthur Cancer Therapy Centre,Campbelltown Hospital, Campbelltown, NSW, Australia
  4. Medical Oncology, Bankstown Cancer Centre, Bankstown-Lidcombe Hospital, Bankstown, NSW, Australia
  5. Ingham Institute, Liverpool, NSW, Australia
  6. Radiation Oncology, Liverpool Cancer Therapy Centre,Liverpool Hospital, Liverpool, NSW, Australia
  7. Radiation Oncology, Macarthur Cancer Therapy Centre,Campbelltown Hospital, Campbelltown, NSW, Australia
  8. Radiation Oncology, Bankstown-Lidcombe Hospital, Bankstown, NSW, Australia
  9. The University of Sydney, Sydney, NSW, Australia
  10. The University of NSW, Sydney, NSW, Australia

Aim: We sought to examine the significance and utility of serial serum CA15-3 levels in assessing disease progression in patients with MBC receiving systemic therapy.

Methods: We reviewed records of consecutive MBC patients treated between 01/01/2012 & 30/08/2016 in SWSLHD to identify those with at least three serial serum CA15-3 levels and one progress imaging study during systemic therapy. The serial percentage change in CA15-3 was calculated and each significant rise in CA15-3 was compared with corresponding radiological or clinical evidence of progression. Disease biology and sites of disease were also examined.

Results: From 141 eligible patients there were 2217 occasions of measured CA15-3 levels. Overall, the median CA15-3 level was 40ku/L (range 3-22320). CA15-3 levels varied according to HER2/ER as follows: HER2+ve (median 28ku/L, range 6-3674), HER2-ve (48ku/L, range 3-22320), ER+ve (45ku/L, range 3-22320), ER-ve (28ku/L, range 6-2188) and triple negative (median 20ku/L, range 6-536). Median CA15-3 levels also varied according to metastatic site. In 1469 instances where the CA15-3 rise was less than 20%, there was no radiological evidence of disease progression (negative predictive value= 83%). In 151 instances, CA15-3 levels increased by 20% or more and corresponded with progression (positive predictive value = 34%). In 1672 instances where the CA15-3 level increased by less than 50%, there was no demonstrated disease progression (negative predictive value = 81%) and in 77 cases of CA15-3 increases of greater than 50% there was demonstrated disease progression (positive predictive value 47%). For 20% increase in CA15-3, the sensitivity was 33% and specificity 83% and for increase of 50%, sensitivity was 17% and specificity was 95%.

Conclusion: Our study suggests that CA15-3 increases of greater than 50% may be more useful than lower thresholds for assessing disease progression during systemic therapy for MBC. Prospective studies are required to further test this threshold.