Benefit is not proven -- use can only be justified within controlled clinical trials at present
Due to a lack of suitable studies, it is unclear whether patients with soft tissue sarcoma can benefit from autologous haematopoietic stem cell transplantation. With this type of therapy, some of the patient's own (autologous) stem cells are removed at a convenient time and generally re-implanted after a course of high-dose chemotherapy. At present, there is neither indication nor proof of additional benefit compared to conventional chemotherapy. Owing to current gaps in knowledge, autologous stem cell transplantation for this disease should only be used within controlled trials at present. This is the conclusion of the final report of the Institute for Quality and Efficiency in Health Care (IQWiG), published on 25 November 2009.
Relatively rare type of cancer: 2,500 cases in Germany annually
Soft tissue sarcomas are malignant tumours whose tissue structure is similar to the soft tissues of the human body, particularly muscle, fat or supporting tissue. They often originate from these soft tissues. These tumours can appear anywhere in the body, with the lower extremities, i.e. legs, being the most frequently affected. This is a relatively rare type of cancer: the annual number of newly diagnosed cases in Germany is estimated at 2,500. Studies of patients with a tumour from the Ewing family of tumours were not included in the evaluation, as here the differentiation between soft tissue and bone tumours is not always clear-cut.
Often a soft tissue sarcoma first manifests itself as a painless ulcer. It may cause pain when, for instance, it presses on other organs, which in turn might restrict their functioning. The tumour becomes life-threatening when it spreads to other organs or forms metastases in other parts of the body ("high-risk patients").
Tumours frequently recur
Surgery is the standard treatment for patients with a localized soft tissue sarcoma, whereas patients with distant metastases generally undergo chemotherapy. The aim is to kill off the cancer cells.
Even if the chemotherapy appears to be successful, the disease soon recurs in a high number of patients. In certain cases, therefore, it is recommended that high-dose chemotherapy and autologous stem cell transplantation is followed immediately. Autologous stem cell transplantation is a planned rescue therapy for high-dose chemotherapy-related severe haematological toxicity. The increased dose is intended to reach those hidden cancer cells that may have hitherto survived - at least this is the assumption of this experimental procedure. However, the cancer cells may be resistant to the chemotherapy, irrespective of the size of the dose.
Autologous stem cell transplantation: stem cells are donated by patients
This type of high-dose chemotherapy usually damages vital haematopoietic stem cells in addition to the tumour cells. Consequently, stem cells are removed from the patient before the treatment and re-implanted afterwards. These stem cells mostly colonize the bone marrow and stimulate haematopoiesis. If the transferred stem cells originate from the patient, this is known as autologous stem cell transplantation. IQWiG did not investigate allogenic stem cell transplantation, where the cells are donated by a donor.
IQWiG investigates benefit for high-risk patients
The focus of this report published by IQWiG is on "high-risk patients": these are patients who have an advanced localized or metastasized soft tissue sarcoma. In order to assess the benefit of autologous stem cell transplantation, IQWiG and its external experts compared the treatment results of patients with and without stem cell transplantation as presented in the scientific literature currently available.
Studies without a control group were also included
As with the disease itself, stem cell transplantation for soft tissue sarcomas is relatively rare. In 2005, for example, the European Group for Blood and Marrow Transplantation (EBMT) reported a total of only 69 autologous stem cell transplants as a result of a soft tissue sarcoma diagnosis. Considering the low number of cases and the probability of a low number of clinical trials overall, IQWiG and its external experts did not limit their search to specific study types.