Trastuzumab is a humanized antibody, designed to target and block the function of HER2, a protein produced by a specific gene with cancer-causing potential. The mode of action of trastuzumab is unique in that it activates the body’s immune system and suppresses HER2 to target and destroy the tumor. trastuzumab has demonstrated unprecedented efficacy in treating both early and advanced (metastatic) HER2-positive breast cancer.
The approval of trastuzumab in combination with chemotherapy for the treatment of metastatic stomic cancer is based on the impressive results from the international ToGA trial, which showed that treatment with trastuzumab significantly prolongs the lives of patients with this aggressive cancer. Overall survival for patients with high levels of HER2 in the ToGA study was 16 months versus 11.8 months (on average) for patients receiving chemotherapy alone [1]
“Herceptin is the first targeted biological therapy to show a survival benefit in advanced stomach cancer and represents a significant advance in the treatment of this devastating disease”, said Pascal Soriot, Chief Operating Officer of, Roche’s Pharmaceutical Division. “We believe that Herceptin will help patients with HER2-positive stomach cancer, as much as it has helped so many women with HER2-positive breast cancer.”
Based on the strong results from the phase III ToGA study, the submission for the label extension was reviewed in an accelerated process by the European Health Authorities, allowing patients to benefit sooner from this life-extending treatment. This marketing authorization is valid with immediate effect in all European Union (EU) and EEA-EFTA states (Iceland, Liechtenstein and Norway). Following approval in the European Union, approvals for a label extension for trastuzumab in other regions of the world are expected to follow soon.
“I am delighted that today’s approval will make Herceptin available to patients with HER-2 positive metastatic stomach cancer across Europe,” said Professor Eric Van Cutsem, University Hospital Gasthuisberg, Leuven, Belgium, one of the lead investigators of the ToGA trial. “The approval of Herceptin for HER2-positive stomach cancer represents an important advance for the treatment of these patients. Clinicians will need to ensure that patients with metastatic stomach cancer are accurately tested for HER2 expression.”
Diagnosis and treatment
Stomach cancer is the second most common cause of cancer-related death in the world and is the fourth most commonly diagnosed cancer, with over 1,000,000 cases of stomach cancer diagnosed each year [2] Advanced stomach cancer is associated with a poor prognosis; the median survival time after diagnosis is approximately 10-11 months with currently available therapies. [3] Approximately 15 - 18% of stomach tumours show high levels of HER2 [4,5]. Early diagnosis of this disease is challenging because most patients do not show symptoms in the early stage.
ToGA is the first randomized Phase III trial investigating the use of trastuzumab in patients with inoperable locally advanced, recurrent and/or metastatic HER2-positive stomach cancer. Approximately 3,800 patients were tested for HER2-positive tumors and 594 patients with HER2-positive disease were enrolled into the study. The rationale for conducting this trial was based on the knowledge that the targeted therapy trastuzumab has demonstrated unprecedented efficacy in the treatment of HER2-positive breast cancer. In addition, the overexpression of HER2 was also observed in stomach cancer. Targeted cancer therapies are drugs or other substances that block the growth and spread of cancer by interfering with specific molecules involved in tumor growth and progression.
In the ToGA study, patients were randomized to receive one of the following regimens as their first line of treatment:
- A fluoropyrimidine (capecitabine (xeloda) or intravenous 5-FU (5-fluorouracil)) and cisplatin every 3 weeks for 6 cycles. Most patients were receiving capecitabine and cisplatin as chemotherapy
- Trastuzumab 6mg/kg every 3 weeks until progression in combination with a fluoropyrimidine and cisplatin for 6 cycles
The primary objective of the study was to demonstrate superiority in overall survival of the trastuzumab containing treatment arm compared to the chemotherapy alone arm. The pre-planned interim analysis was triggered by the occurrence of 347 events. Secondary endpoints for the study included progression-free survival, overall response rate, duration of response, safety and quality of life. In the ToGA study, no new or unexpected side effects were observed. For overall survival, the Hazard Ratio was 0.74 (CI 0.60, 0.91) with a highly significant p-value of p=0,0046.
Trastuzumab increased the median overall survival time by 2.7 months to 13.8 months (intent to treat patient group, defined as IHC3+ or FISH-positive, represented 22% of patients tested for HER2 in the ToGA study). The response rate was increased with trastuzumab from 34.5 % to 47.3%. Patients with tumors exhibiting high levels of HER2 (IHC3+ or IHC2+/FISH-positive, 16% of patients tested for HER2 in the ToGA study) experienced even greater benefit from the addition of trastuzumab. For these patients, overall survival in the study was 16 months on average versus 11.8 months for patients receiving chemotherapy alone. The EU label recommends trastuzumab for patients expressing high levels of HER2.
Personalized Healthcare: Fitting treatments to patients
Different people respond differently to medicines. The aim of aim of a personalized approach to healthcare is to target treatments to the patients most likely to benefit. This means tailoring treatments to specific patient sub-groups who share similar characteristics in their genetic makeup or in the molecular nature of their disease. This approach has enormous potential to make healthcare better, safer and more effective, with benefits for patients, physicians, payers, and society at large.
Trastuzumab treatment in breast cancer is a case in point: Measuring the levels of the protein HER2 in breast cancer cells with specific tests reliably identifies patients who are likely to respond to trastuzumab. The same approach can also be applied in the diagnosis and the treatment of HER2-positive metastatic gastric cancer with trastuzumab.
References
[1]Van Cutsem et al. Abstract #7BA ECCO/ESMO 2009
[2]American Cancer Society. Global Cancer Facts & Figures 2007
[3] Ohtsu A. J Gastroenterol 2008;43:256-264
[4] Hofmann M, Stoss O, Shi D, Buttner R, van d, V, Kim W et al. Assessment of a HER2 scoring system for gastric cancer: results from a validation study. Histopathology 2008; 52(7):797-805.
[5] Park DI, Yun JW, Park JH, Oh SJ, Kim HJ, Cho YK et al. HER-2/neu amplification is an independent prognostic factor in gastric cancer. Dig Dis Sci 2006; 51(8):1371-1379.
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