Feb 10 2015
Researchers at the Princess Margaret Cancer Centre are proposing a new model to enable doctors to predict outcomes more accurately for patients with throat cancers specifically caused by Human Papillomavirus (HPV).
The findings are published online today in the Journal of Clinical Oncology. Study investigators, Dr. Brian O'Sullivan, Lead, Head and Neck Cancer Site Group and Shao-Hui Huang, Research and Clinical Radiation Therapist at Princess Margaret Cancer Centre, have determined that a new model for classifying the most frequently seen throat cancers in our geographic location is needed. This classification incorporates individual patient factors including age and their smoking status with the traditional classification of the extent of disease, to offer a more personalized approach to predict outcomes and guide treatment.
"Our study shows that the current model derived for smoking and alcohol related cancers is not suited for throat cancer caused by HPV, a burgeoning throat cancer population in the Western World, including Canada," says Huang.
"This is the future of tumour staging. We need to consider the patient as a whole. Both individual factors, how extensive the disease is in the patient, and tumour biology should play a role in determining the best course of treatment."
The purpose of a tumour staging system is to classify the disease into early, intermediate or advanced stage cancer. This classification helps determine treatment plans and can suggest what is likely to be the outcome. In recent years, it's been discovered that throat cancer caused by HPV behaves differently than throat cancer caused by smoking and alcohol, yet both cancers use the same tumour classification model. Therefore, regardless of whether the cancer was caused by HPV or smoking, the treatment and perceived prognosis based on tumour staging has remained the same - even though patient outcomes, as this study demonstrates, vary considerably.
For example, a stage IV patient with HPV-related cancer has an 80 per cent survival rate while a stage IV smoking-related cancer patient has a 50-60 percent survival rate, but both are presently considered advanced stage - which is recognized as a life-threatening prognosis.
"When you tell a patient they have stage IV cancer, it's an indication of advanced disease and they don't expect it to be curable," says Huang. "We need a staging system that more accurately reflects a patient's prognosis - which in a case caused by HPV, is highly curable."
The study also highlights the fact that many HPV-related throat cancer patients are over-treated due to the stage IV tumour classification. High dose chemotherapy combined with high dose radiation is often given to this patient population when radiation therapy alone or other less intensive strategies can probably cure many of them.
Clinical trials have now begun to address these questions but their descriptions and design are hindered by inadequacies of the current stage classification. A new tumour staging model will help to separate patients with promising prognoses from those with negative prognoses to design the most appropriate treatment strategies for each group.
"This work has several interesting characteristics, and not just relating to the management of head and neck cancer. Providing a relevant stage classification for a rapidly emerging disease is important, but the additional feature of the classification is that it provides the opportunity to include factors beyond just the traditional description of disease extent into the prognostic classification we are trying to develop to assist in treating patients," says Dr. O'Sullivan.
"The structure used for the classification follows a template we developed at the Union for International Cancer Control (UICC) and is relevant to all cancers. Important factors that are emerging throughout oncology are not currently included in the international classifications. This needs to change to facilitate our goal of providing personalized approaches to patients with cancer."
The Princess Margaret is collaborating with six major cancer centres across the world to validate these findings, which will provide solid evidence for a new tumour staging system that offers a personalized approach to medicine.
Princess Margaret Cancer Centre, University Health Network