Cabozantinib as a Treatment for Ewing Sarcoma and Osteosarcoma

Cabozantinib has recently been studied as a treatment for Ewing sarcoma and osteosarcoma. It demonstrated antitumor activity in both of these cancers, which was discovered in the second phase of the CABONE study.

About Ewing Sarcoma

Ewing sarcoma is a rare form of cancer that begins in the bones or the soft tissue surrounding them. This cancer can take place in any bone, but most commonly starts in the long bones of the pelvis, legs, and arms. At times it can also begin in the soft tissue of the arms, legs, abdomen, or other parts of the body. While it is most likely to affect teenagers and young adults, Ewing sarcoma can affect people of any age.

The cause of this cancer is unknown. There are genes that have been found to be linked to Ewing sarcoma, but it is not thought to be an inherited disease. Healthcare professionals are also unsure of the risk factors that may be associated with this cancer.

Symptoms of Ewing sarcoma are pain, swelling, tenderness, bone pain that can worsen with physical activity or at night, unexplained fatigue, fever, unintentional weight loss, or broken bones without a known cause. There are also complications associated with Ewing sarcoma. This cancer can spread to other parts of the body, which makes treatment and recovery more difficult. It can also return after treatment.

It is typically noticed when people are brought in for sprains or other injuries, and x-rays reveal that there is something more behind the pain. Further imaging tests are usually necessary. CT scans, MRIs, PET scans, and bone scans may all be ordered. Biopsies are ordered after these tests, either needle or surgical biopsies.

Treatment for Ewing sarcoma includes chemotherapy, radiation, surgery, or clinical trials. There have been many advances in the treatment of this disease over the years, so outlooks for patients are much better than they once were.

About Osteosarcoma

Osteosarcoma is a form of bone cancer, and it typically occurs in places where the bones grow quickly. Teens experiencing growth spurts are often affected by osteosarcoma, and males are more commonly affected. It is the most common form of bone cancer. The exact cause is unknown, but some cases have been linked to a gene that is passed through families which increases the risk of developing this cancer.

The location of the tumor influences the symptoms, but common symptoms include bone fractures and pain, swelling, limping, limitation of movement, and redness. Unfortunately, early symptoms are often overlooked or written off as growing pains, which can impact the diagnosis of this cancer and stop early treatment.

A physical exam is the first step in the diagnostic process, followed by a blood test. Doctors may also perform CT scans, X-rays, MRIs, PET scans, and biopsies. After a diagnosis is confirmed, treatment often consists of surgery and chemotherapy.

CABONE Study

This study was conducted in multiple centers as a single-arm, two phase trial. All participants were older than 12 and had documented disease progression. Prior treatment was not a defining factor in participation, unless they had received chemotherapy or biologic therapy in the weeks before the trial. In total, there were 39 patients with Ewing sarcoma and 42 with osteosarcoma.

All participants took cabozantinib once a day for 28 day cycles until they revoked their consent, or researchers decided to discontinue treatment. The majority of participants were included in the safety and efficacy analysis. The primary endpoint for both cancers was six month objective response, while the osteosarcoma portion of the study also looked for the six month non-progression assessment.

Results of this study showed that 26% of Ewing sarcoma patients achieved the six month objective response, and every response within the study was a partial response. In the osteosarcoma portion, 12% of participants saw a six month objective response, and 33% had six months of no progression.

Not only did a percentage of patients meet the primary endpoints, but 49% of Ewing sarcoma patients saw a stable disease, with another 38% seeing their tumors shrink. The length of progression free survival for Ewing sarcoma was 4.4 months, with the median overall survival at 10.2 months. In the osteosarcoma portion, 62% of participants saw a stable disease, and 33% had tumors shrink. 6.7 months was the length of progression free survival, compared to a median overall survival of 10.6 months.

All of the results of this study point to cabozantinib as a viable treatment for these cancers. Further research will be done so that medical professionals can fully understand this medication and how it can best help those with osteosarcoma and Ewing sarcoma.

Read more about the study here.

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