The monoclonal antibodies (moAb) panitumumab and cetuximab target the epidermal growth factor receptor (EGFR) and have proven valuable for the treatment of metastatic colorectal cancer (mCRC). EGFR-mediated signaling involves two main intracellular cascades: on one side KRAS activates BRAF, which in turn triggers the mitogen-activated protein kinases. On the other, membrane localization of the lipid kinase PIK3CA counteracts PTEN and promotes AKT1 phosphorylation, thereby activating a parallel intracellular axis. Constitutive activation of KRAS bypasses the corresponding signaling cascade and, accordingly, patients with mCRC bearing KRAS mutations are clinically resistant to therapy with panitumumab or cetuximab. We hypothesized that mutations activating PIK3CA could also preclude responsiveness to EGFR-targeted moAbs through a similar mechanism. Here, we present the mutational analysis of PIK3CA and KRAS and evaluation of the PTEN protein status in a cohort of 110 patients with mCRC treated with anti-EGFR moAbs. We observed 15 (13.6%) PIK3CA and 32 (29.0%) KRAS mutations. PIK3CA mutations were significantly associated with clinical resistance to panitumumab or cetuximab; none of the mutated patients achieved objective response (P = 0.038). When only KRAS wild-type tumors were analyzed, the statistical correlation was stronger (P = 0.016). Patients with PIK3CA mutations displayed a worse clinical outcome also in terms of progression-free survival (P = 0.035). Our data indicate that PIK3CA mutations can independently hamper the therapeutic response to panitumumab or cetuximab in mCRC. When the molecular status of the PIK3CA/PTEN and KRAS pathways are concomitantly ascertained, up to 70% of mCRC patients unlikely to respond to EGFR moAbs can be identified.

Adding oxaliplatin to fluorouracil-based preoperative chemoradiotherapy significantly increases toxicity without affecting primary tumor response. Longer follow-up is needed to assess the impact on efficacy end points.

BACKGROUND Chromogranin A (CgA), neuron specific enolase (NSE), carcinoembryonic antigen (CEA), and urinary 5‐hydroxyindole‐3‐acetic acid (5‐HIAA) are the markers currently used in the diagnosis, prognosis, and follow‐up of patients with neuroendocrine tumors (NETs). The authors examined the role of such biomarkers in a large series of patients with NETs. METHODS One hundred and twenty‐seven patients entered the study. Multiple blood and 24‐hour urine specimens were assayed for biomarker quantitation. RESULTS The accuracy of each marker was assessed in patients with (n = 106) and without (n = 21) disease. CgA proved to be the best marker (specificity of 85.7% and sensitivity of 67.9%). Patients with disease had significantly higher CgA and NSE levels compared with disease free patients (P = 0.00003 and P = 0.00240, respectively). NSE and 5‐HIAA determination showed a very high specificity (100%) but a rather low sensitivity (32.9% and 35.1%, respectively). CEA was found to have little diagnostic value (sensitivity of 15.4%). CgA was the most sensitive marker for detecting patients with disseminated disease and 5‐HIAA displayed the highest sensitivity in identifying syndromic patients. Tumor marker modifications were studied during follow‐up. In particular, rises in CgA were associated with progressive disease in 83.3% of cases and stable CgA was associated with stable disease in 53.8% of cases. The relation between CgA modifications and liver lesions during follow‐up also was studied; increases in CgA levels were associated with local progression in 100% of cases and stable marker levels were found in 68.7% of the patients with unchanged lesions. CONCLUSIONS The results of the current study demonstrate that CgA has the highest accuracy and is the most reliable biomarker reflecting the clinical evolution of NETs. Cancer 1999;86:858–65. © 1999 American Cancer Society.