Biomarkers in gastrointestinal stromal tumor: should we equate blood-based pharmacodynamics with tumor biology and clinical outcomes?

Added value of molecular targeted agents in oncology

The treatment of certain cancers has been revolutionised in recent years by the introduction of novel drugs designed to target specific molecular factors implicated in tumour growth. Notable examples include trastuzumab, a humanized monoclonal antibody (mAb) against human epidermal growth factor receptor (HER)-2 in women with HER2-positive breast cancer; rituximab, an anti-CD20 mAb in patients with non-Hodgkin's lymphoma; imatinib, a tyrosine kinase inhibitor in KIT-positive gastrointestinal stromal tumours and sunitinib, another tyrosine kinase inhibitor, in metastatic renal cell carcinoma. For regulatory reasons, new molecular targeted agents are first evaluated in advanced and metastatic disease, wherein they prolong survival. However, their most profound impact has been observed in the adjuvant setting, where they may contribute to curative therapy rather than mere palliation. Expansion in the use of molecular targeted therapies will have important cost implications for health care systems. Although expensive, on a monthly basis, molecular targeted therapies may not be more costly than treatments for other major chronic diseases, especially considering the contribution of cancer to the global disease burden, the associated socioeconomic costs and the long-term benefits of therapy. Nevertheless, the use of these agents must be optimised, in part using molecular biomarkers associated with drug response.

Phase I trial of a combination of the multikinase inhibitor sorafenib and the farnesyltransferase inhibitor tipifarnib in advanced malignancies

PURPOSE

We evaluated the safety, maximum tolerated dose, pharmacokinetics, and biological effects of the combination of the Raf-1, RET, KIT, platelet-derived growth factor receptor, and vascular endothelial growth factor receptor 2 kinase inhibitor sorafenib and the farnesyltransferase inhibitor tipifarnib.

EXPERIMENTAL DESIGN

A standard 3 + 3 phase I dose-escalation design was used with a 28-day cycle (sorafenib daily and tipifarnib for 21 days, by mouth).

RESULTS

Fifty patients were treated; 43 reached restaging evaluation after cycle 2. The most common side effects were grade 1 to 2 rash, hyperglycemia, and diarrhea. Dose-limiting toxicity was rash, and the recommended phase II dose is sorafenib 400 mg p.o. qam/200 mg p.o. qpm and tipifarnib p.o. 100 mg bd. Despite the low doses of tipifarnib, one quarter of patients had > or =50% reduction in farnesyltransferase levels. Interestingly, six of eight patients with medullary thyroid cancer had durable stable disease (n = 3) or partial remissions (n = 3), lasting 12 to 26+ months. Five of the six responders had available tissue, and RET gene mutations were identified in them. Prolonged (> or =6 months) stable disease was also seen in nine patients as follows: papillary thyroid cancer (n = 4; 18+ to 27+ months), adrenocortical cancer (n = 2; 7 and 11 months), and one each of melanoma (platelet-derived growth factor receptor mutation positive; 14 months), renal (6 months), and pancreatic cancer (6 months).

CONCLUSIONS

Our study shows that the combination of tipifarnib and sorafenib is well tolerated. Activity was seen, especially in patients with medullary thyroid cancer, a tumor characterized by RET mutations.

Circulating endothelial cells in non-small cell lung cancer patients treated with carboplatin and paclitaxel

INTRODUCTION

Circulating endothelial cells (CECs) increase in cancer patients and play an important role in tumor neovascularization.

METHODS

This study was designed to investigate the role of CEC as a marker for predicting the effectiveness of a carboplatin plus paclitaxel based first line chemotherapy in advanced non-small cell lung cancer (NSCLC).

RESULTS

The CEC count in 4 ml of peripheral blood before starting chemotherapy (baseline value) was significantly higher in NSCLC patients, ranging from 32 to 4501/4 ml (n = 31, mean +/- SD = 595 +/- 832), than in healthy volunteers (n = 53, 46.2 +/- 86.3). We did not detect a significant correlation between the CEC count and estimated tumor volume. CECs were significantly decreased by chemotherapy as compared with pretreatment values (175.6 +/- 24 and 173.0 +/- 24, day +8, +22, respectively). We investigated the correlation between baseline CEC and the clinical effectiveness of chemotherapy. CEC values are significantly higher in patients with clinical benefit (partial response and stable disease, 516 +/- 458, 870.8 +/- 1215, respectively) than in progressive disease patients (211 +/- 150). Furthermore, a statistically significant decrease in CECs, on day 22, was observed only in patients with partial response. Patients who had a baseline CEC count greater than 400/4 ml showed a longer progression-free survival (>400, 271 days [range: 181-361] versus <400, 34 [range: 81-186], p = 0.019).

CONCLUSION

CEC is suggested to be a promising predictive marker of the clinical efficacy of the CBDCA plus paclitaxel regimen in patients with NSCLC.