Rare primary malignant bone sarcoma (RPMBS) is a term for rare bone cancers, and they account for no more than a tenth of fast-growing bone tumours. It can be difficult to research RPMBS as they are so rare. This slows down the development of new treatments. RPMBS also usually affect an older adult population. This means there are more concerns about side effects from chemotherapy. To increase knowledge in this area, multiple centres came together. They ran a clinical trial that looked at the effects of a specific form of treatment on patients with RPMBS. In this blog, we take a look at the clinical trial and discuss why the trial is relevant to osteosarcoma.
Clinical trial: What, who and how?
The clinical trial assessed the use of an OS-like chemotherapy treatment on patients. Multiagent chemotherapy was used which is a form of treatment consisting of two or more drugs and is usually given to patients with OS. Patients were recruited by centres in Europe. 122 patients with RPMBS were identified and out of that group, 113 patients were analysed. They were aged between 41 to 65. Their RPMBS were undifferentiated pleomorphic sarcoma, leiomyosarcoma (LMS), fibrosarcoma and angiosarcoma of the bone.
The treatment included surgical removal of the cancer. Multiagent chemotherapy was given either before and after the surgery (like in OS) or only after the surgery to all patients in this study.
The patients were followed-up at a later date to learn whether or not the treatment had been effective and to what extent. 109 out of the 113 patients underwent surgery and 96 patients received chemotherapy after their surgery. Some patients also received chemotherapy before surgery. The trial revealed some interesting findings. Patients with LMS of the bone usually show poor responses to treatment. In this trial, more than half of the patients with this cancer showed a five-year survival rate. Although this is not a high success rate, it is an improvement. Similar results were seen in the other RPMBS. A finding which differs from the usual responses to chemotherapy in OS, was patients’ responses to chemotherapy before surgery. Data shows that more than half of OS patients respond well to this type of chemotherapy, but in this trial, less than a quarter of patients showed a good response. However, any delay to surgery caused by this did not affect outcomes.
Overall, the study reports that patients with OS and RPMBS display ‘almost identical’ outcomes when treated with OS-like chemotherapy. Additionally, the chemotherapy appeared safe in older adults.
What does this mean?
Based on these results, the researchers suggest that multiagent chemotherapy could be used as an option for patients aged between 41 to 65 years who have certain rare bone tumours.
As RPMBS and OS patients were affected similarly by the same form of treatment, it could mean that both conditions have more in common than we think. If OS-like treatment is relevant in RPMBS cases, can certain aspects of RPMBS such as their mechanisms be relevant in our understanding of OS?
This trial shows us that treatments designed for certain cancers may be used for other cancers. There could be treatments that are currently aimed at other cancers but may also be effective in OS. To advance our knowledge on how to treat OS, we can conduct trials like this that allow us to compare and contrast treatment responses between conditions.