579P - Assessment and comparison of treatment efficacy in patients with colorectal cancer (CRC), using a novel methodology to estimate the rate of tumor re...

Date 01 October 2012
Event ESMO Congress 2012
Session Poster presentation III
Topics Colon Cancer
Rectal Cancer
Presenter Montserrat Blanco Codesido
Authors M. Blanco Codesido1, J. Wilkerson2, L. Rodriguez Gayo3, M. Rodriguez Alonso3, P. Nava Garcia3, A. Matas Ochoa3, A.J. Muñoz Martín3, S. Alvarez Suarez3, P. García Alfonso4, T. Fojo2
  • 1Servicio De Oncología Médica, Hospital General Univ. Gregorio Marañon, 28007 - Madrid/ES
  • 2Medical Oncology Branch Center For Cancer Research, National Cancer Institute, 20892 - Bethesda/US
  • 3Servicio Oncología, Hospital Universitario Gregorio Marañon, 28007 - Madrid/ES
  • 4Medical Oncology, Hospital Universitario Gregorio Marañon, 28007 - Madrid/ES

Abstract

Introduction

Novel methods of assessing treatment efficacy should prove helpful in drug development and in the management of cancer patients (pts). We have developed a novel method to analyze tumor response to therapy by quantifying the rate of tumor regression (d) and growth (g). We have shown g is slower when pts are on effective therapy and that g correlates with survival. We utilized this novel methodology in pts with a diagnosis of CRC to compare the efficacy of oxaliplatin- and irinotecan-containing regimens (OCR, ICR). Unlike PFS, an incremental measure of efficacy, g is a continuous variable and can more accurately assess differences between treatments. Because calculations of g are indifferent to assessment intervals, estimating a tumor's g allows comparison of efficacy across trials.

Methods

Using tumor measurements obtained for RECIST assessments or serum CEA levels and a two-phase mathematical equation we determined d and g in 70 pts at each evaluation.

Results

70 pts (47 male, 23 female) with metastatic CRC were studied. The median g value with OCR (.00132) was statistically similar (p = 0.573) to that observed with ICR (.00148). Both therapies also had similar effects on d (OCR = 0.00529; ICR = 0.00451; p = 0.716). Similar results were seen using serum CEA levels. Furthermore, in an individual pt, statistically valid g and d values could be estimated long before tumor quantity increased, providing an early indicator of treatment failure. Importantly, in the majority of pts receiving prolonged treatment the growth rate constant did not change, despite rising tumor quantities, indicating resistance is intrinsic. Additional data being gathered should allow us to compare relative effects on g in first and subsequent lines to discriminate between the effects observed in tumor shrinkage and the impact on tumor growth.

Conclusions

In this cohort of CRC patients the data suggest both OCR and ICR have similar efficacy. The evidence in pts receiving long term therapy demonstrating no change in g over time suggest resistance is intrinsic and not acquired, and would support a strategy of continued treatment with a tolerable regimen given the similar efficacy of the commonly used combinations.

Disclosure

All authors have declared no conflicts of interest.