Panitumumab treatment of progressive therapy-resistant colorectal cancer

This study investigated the treatment of progressive therapy-resistant colorectal cancer with panitumumab (Vectibix). It was found that panitumumab was a safe and effective treatment for CRC patients who had progressed despite treatment.

Chemotherapy is generally the first treatment option for colorectal cancer (CRC). Some patients progress despite treatment. It can be difficult to make treatment choices for CRC which has been resistant to therapy.

Treatments such as panitumumab and cetuximab (Erbitux) can be effective in these cases. These therapies block the activity of the epidermal growth factor receptor (EGFR) that increases cancer cell growth. Treatment with panitumumab leads to skin toxicities (STs), such as rash, in most patients. It has been shown that the severity of such side effects is associated with treatment outcome.

This study aimed to determine the safety and effectiveness of panitumumab in the treatment of CRC patients who had previously been treated with the chemotherapy combination of 5-fluorouracil (Efudex), oxaliplatin (Eloxatin), and irinotecan (Camptosar). 570 patients were treated with 6 mg/kg of panitumumab every 2 weeks for an average of 9.6 treatment cycles. Patients were followed for up to 36 weeks. Disease control rate (lack of tumor growth) and side effects were monitored.

84.3% patients reported STs. Rash was the most common side effect, occurring in 73.7% of patients. The average time before the development of the first side effect was 17.3 days. 82.7% of patients who developed STs required treatment.

The average DCR rate at the end of the study was 58.9%. ST severity was associated with treatment outcome. In patients with minor STs, the disease control rate after treatment was 53.8%. In comparison, patients with moderate to severe STs had a DCR of  62.7%.  Tumor response and survival without disease progression was better in patients with more severe STs compared to those with minor STs. Patients who had fewer chemotherapy treatments prior to panitumumab therapy had a better response.

The authors concluded that panitumumab appeared to be a safe and effective treatment for CRC which has been unresponsive to other treatments.

The author received fees from Amgen and other pharmaceutical companies that produce drugs used to treat CRC. 

Consult your doctor regarding treatment options beyond chemotherapy.