A Point, a Line, or an Area? Which Is the Most Important in the Pharmacological Analysis of Cancer Chemotherapy?

Efficacy and safety of single-agent pertuzumab (rhuMAb 2C4), a human epidermal growth factor receptor dimerization inhibitor, in castration-resistant prostate cancer after progression from taxane-based therapy

PURPOSE

Pertuzumab represents a new class of targeted anticancer agents, human epidermal growth factor receptor (HER) dimerization inhibitors. The aim of this single-arm phase II clinical study was to assess the efficacy and safety of single-agent pertuzumab in castration-resistant prostate cancer (CRPC) patients who had experienced progression after prior chemotherapy.

PATIENTS AND METHODS

Patients received pertuzumab every 3 weeks. All castration-resistant patients had experienced progression after at least one taxane-based regimen. Patients received a loading dose of 840 mg pertuzumab (cycle 1) followed by 420 mg for subsequent cycles. The primary end point was overall response and safety. A separate retrospective analysis of actual survival time versus predicted survival time for a patient population with comparable prognostic features was performed.

RESULTS

Patients were enrolled (N = 42) and treated (n = 41). No patients had complete or partial response (as defined by Response Evaluation Criteria in Solid Tumors Group or 50% decline in prostate-specific antigen). Of 30 efficacy-assessable patients, five had stable disease (SD) for at least 23 weeks; one of five had SD for 36 weeks. Pertuzumab was well tolerated; diarrhea was the most common adverse effect (61.0%, grades 1 to 3). Retrospective analysis of survival using a validated nomogram suggested that survival was prolonged with pertuzumab treatment, compared with historic controls with similar baseline prognostic features.

CONCLUSION

Pertuzumab was well tolerated and resulted in no objective responses, but several patients had SD more than 23 weeks from a heavily pretreated population. Retrospective analysis suggested prolonged median survival time with pertuzumab compared with historical controls. Thus, inhibition of HER dimerization may have clinical utility in CRPC patients.

Chemotherapy Dosing Part I: Scientific Basis for Current Practice and Use of Body Surface Area

Cytotoxic chemotherapy is characterised by a low therapeutic index and significant variability in therapeutic and toxic effects. In an attempt to reduce this variability, most chemotherapy doses are individualised according to patient body surface area (BSA). This practice, which was introduced almost 50 years ago, clearly has practical and economic implications for the healthcare system. Furthermore, the clinical value of this approach has, in recent years, been questioned. Despite established practice, chemotherapy dose selection remains complicated, partly because treatment effects are difficult to measure, partly because drugs are used in combination with other treatment modalities, and also because the patient's condition may change with disease progression. Various patient-related factors can affect drug pharmacokinetics (PK) and pharmacodynamics (PD), for example organ function, expression and activity of metabolising enzymes, drug resistance, body size, gender, age, concomitant disease and co-administration of other drugs. These factors may be of clinical significance in chemotherapy dose determination and measures of PK, PD or both feature in attempts to devise more rigorous methods for chemotherapy dosing. Part I of this series of two reviews describes the history and clinical impact of BSA-based chemotherapy, and examines the scientific evidence to support BSA dosing. It evaluates the factors affecting PK and PD for specific drugs that could inform and refine dose determination.