Soft tissue sarcoma is a type of cancer that begins in body tissue like fat, muscle, nerves or blood vessels. Sarcoma can occur anywhere in the body, including the arms and legs, and there are upwards of 50 soft tissue sarcoma subtypes. These variations add to the complexity of both treating this rare disease and discovering new effective therapies.
When localized, sarcoma is removed by surgery if possible, often in combination with radiation therapy. However, when sarcoma spreads, or metastasizes, to other parts of the body, surgery is not always an option. Metastatic, or advanced, sarcoma commonly spreads to the lung or brain depending on the type, but there is no way to definitely detect if or where the cancer will spread.
We oftentimes treat advanced sarcoma with a systemic approach, employing different chemotherapy agents. This can include a single drug or combination of drugs – all depending on the unique characteristics of the individual’s cancer.
Drugs used to treat sarcoma, some of which have been used for more than 30 years while others are relatively new, include but are not limited to the following:
- gemcitabine, oftentimes in combination with docetaxel
- temozolomide (intravenous form: dacarbazine)
Regardless of the particular drug used, the probability of a tumor responding from any single drug remains around 10% to 20% - only one in five. We clearly have a need for more effective drugs, and this need highlights the importance of clinical trials.
A New Option for Advanced Soft Tissue Sarcoma
One such clinical trial resulted in the April 2012 FDA approval of a new drug called pazopanib, or Votrient. Approved for all subtypes of soft tissue sarcoma except adipocytic soft tissue sarcoma and gastrointestinal stromal tumors (GIST), pazopanib was tested in a truly collaborative effort – an international clinical trial of more than 360 patients in more than 72 institutions across 13 countries.
How does pazopanib work?
Pazopanib is among a class of medications known as small molecule inhibitors, or tyrosine kinase inhibitors. Taken as an oral pill, the drug targets a type of protein on cancer cells that supports formation of new blood vessels, which the cells need to grow and spread. By attacking these proteins, pazopanib prohibits the metastatic potential of cancer cells by inhibiting their growth.
While pazopanib did not prove successful in shrinking the tumors of the patients in the study, it did stop or slow tumor growth in nearly two-thirds, or 60%, of the patients. This was a landmark finding because it gives us a new option for controlling progression or spread in advanced sarcoma patients for a longer period of time.
As with most cancers, there is no single treatment option for sarcoma. One size does not fit all. But as we begin to understand more about these cancers, we are better able to target the individual drivers that allow the cancers to grow and thrive. Pazopanib has given patients another option for controlling a cancer that is typically considered an incurable disease.