Early tumor shrinkage and depth of response predict long-term outcome in metastatic colorectal cancer patients treated with first-line chemotherapy plus bevacizumab: results from phase III TRIBE trial by the Gruppo Oncologico del Nord Ovest

BACKGROUND

Early tumor shrinkage (ETS) and depth of response (DoR) predict overall survival (OS) in first-line trials of chemotherapy ± anti-EGFR monoclonal antibodies in metastatic colorectal cancer (mCRC). These associations and the predictive accuracy of response measurements for survival parameters were investigated in the phase III TRIBE trial of FOLFOXIRI plus bevacizumab (bev) versus FOLFIRI plus bev.

PATIENTS AND METHODS

A landmark approach was adopted to define the assessable population. The distribution of RECIST response rate, ETS and DoR was compared in the two arms. Associations between response measurements and progression-free survival (PFS), post-progression survival (PPS) and OS were tested by univariate and multivariate Cox models. Prediction performance of each factor was estimated by C-index.

RESULTS

A significantly higher percentage of patients in the FOLFOXIRI plus bev arm achieved ETS ≥20%, when compared with the control arm (62.7% versus 51.9%, P = 0.025). Also the DoR was significantly higher in the triplet plus bev arm (43.4% versus 37.8%, P = 0.003). Both ETS and DoR were associated with PFS, PPS and OS at the univariate analyses and in the multivariate models stratified for other prognostic variables. Both ETS and DoR were able to predict survival as accurately as RECIST response.

CONCLUSION

FOLFOXIRI plus bev improves ETS and DoR when compared with FOLFIRI plus bev. Achieving rapid and deep tumor shrinkage consistently delays tumor progression and prolongs survival in patients treated with first-line chemotherapy plus bev. ETS is a promising and valuable end point for clinical trials' design deserving further investigation.

Correlation between NK function and response to trastuzumab in metastatic breast cancer

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Background: Trastuzumab is a monoclonal antibody selectively directed against Her2 approved for the treatment of Her2 overexpressing breast cancer patients. Its proposed mechanisms of action include also a role in mediating antibody-dependent cellular cytotoxicity (ADCC), through the triggering of the FcγRIII on natural killer (NK) cells. This study addressed the correlation between overall NK function and clinical trastuzumab activity. Methods: Between March and September 2006 22 metastatic patients in treatment with trastuzumab alone (8 mg/kg load and then 6 mg/kg every 3 weeks until disease progression) as maintaining therapy after chemotherapy were analyzed for clinical and immunological responses. According to RECIST criteria, 14 patients obtained a response to trastuzumab, while 8 patients had a disease progression. Patient’s peripheral blood mononuclear cells were tested for cytotoxic activity against standard NK target (the MHC class I-negative K562 cell line) and trastuzumab-coated MCF7 (Her2-negative) and SKBR3 (Her2-positive) human cell lines in a 4-h 51Cr-release cytotoxicity assay in the presence of grading concentrations of effector cells. Results: NK activity was significantly (p<0.05) higher in responder compared to non responder patients at all the four effector:target (50:1 to 6:1) ratios tested. NK activity of non responder patients was significantly lower than that of 25 sex and age matched controls (p<0.02) and this was not merely due to chemotherapy- or tumor-associated immunosuppression, since the values of responder patients did not significantly differ from those of controls. ADCC activity against Her2-positive SKBR3 cells was also significantly higher in responder compared to non responder patients (p<0.05) and markedly so when compared to controls (p<0.001). Conclusions: The fact that, as shown here, normal levels of FcγR- independent and higher than normal levels of FcγR-dependent cytotoxicity are required for trastuzumab response, lends support to a paramount role of NK cells in the mechanism of action of this drug.

No significant financial relationships to disclose.