Stomach or gastric cancer is the fourth most common cancer in the world, and is second only to lung cancer as a leading cause of cancer death.
In BC, up to 400 new cases of gastric cancer are diagnosed every year, affecting nearly twice as many men as women. Although the prognosis for patients with advanced gastric cancer is generally poor, recent work by a BC Cancer Agency (BCCA) team of pathologists and clinical researchers has led to the adoption of a new targeted therapy for some BC patients with the disease.
The effectiveness of the targeted therapy, using Herceptin – a drug originally developed for treating breast cancer – was first shown in an international study in 2009. The drug is used in cancer patients with an HER-2 gene mutation causing an “over-expression” of protein. The HER-2 mutation occurs in about 15 per cent of patients with advanced gastric cancer, and about 20 per cent of patients with advanced gastro-esophageal junction cancer.
In 2010, BC became the first province in Canada to approve funding for Herceptin as a treatment for HER-2 positive gastric cancer. Because effective use of this new therapy requires being able to accurately test tumours for HER-2 expression, a BCCA-based study was done to validate the pathology findings of the international study, establish a methodology for HER-2 testing at BCCA and confirm the proportion of BC patients who would benefit from the treatment. The study also resulted in the BCCA and the Centre for Translational & Applied Genomics acquiring the specialised equipment and expertise needed for HER-2 testing in gastric cancer.
Dr. Sharlene Gill, a clinical researcher, gastrointestinal oncologist and chair of the GI Tumour Group at BCCA, says:
Gastric cancer has recently become the focus of intense research interest (and) hopefully the extent of that research activity will lead to some new treatment breakthroughs.
“Although we had much experience with HER-2 testing in breast cancer, it’s more difficult when used for gastric cancer,” says pathologist Dr. Chen Zhou, BCCA’s medical director of diagnostic cytology. “Unlike breast cancer tumours which tend to be distinct, in gastric cancers the tumours are diffuse and it can be difficult to know where to look and to differentiate between normal stomach tissue and cancer cells.”
“You want this kind of specialized testing to be done in an established centre with experienced lab staff,” adds clinical researcher Dr. Sharlene Gill, a gastrointestinal oncologist and chair of BCCA’s GI Tumour Group.
“The new in-house expertise acquired through this research program positions BCCA to be recognized as a Western Canadian referral centre for centralized HER-2 testing,” says Gill.
On average, patients with advanced gastric cancer who receive conventional therapy will survive about 12 months, says Zhou. However, for gastric cancer patients with amplified HER-2 gene expression, treatment with Herceptin in combination with chemotherapy can add four to five months of life.
“That may seem like a relatively modest gain, but it’s significant for these patients who up to now have had limited treatment options,” says Gill.
What’s more, following the success of the HER-2 targeted treatment for gastric cancer, Gill says there are now a number of studies looking at promising new targeted pathways for treatment of the disease.
“Gastric cancer has recently become the focus of intense research interest,” says Gill. “Hopefully, the extent of that research activity will lead to some new treatment breakthroughs, which are really needed for patients with this disease.”
Dr. Chen Zhou is a pathologist and medical director of diagnostic cytology at BCCA.
Dr. Sharlene Gill is a clinical researcher, gastrointestinal oncologist and chair of the GI Tumour Group at BCCA.