Abstract
BackgroundThe results of treatment for malignant bone and soft-tissue tumors arising from the deep trunk and pelvis are still not acceptable due to the relatively high recurrence and low overall survival rates. Recently, carbon ion radiotherapy (CIRT) was applied for several malignancies, including bone and soft-tissue sarcomas, and provided favorable results. However, it has been unclear what modalities should be used for evaluating the response and for the follow-up of these patients. Here, we analyzed the methods used to predict local recurrence and to find local failures or metastases.MethodsWe analyzed 37 patients with bone and soft-tissue tumors who received CIRT at our institute. The patients were examined with FDG positron emission tomography (PET) and enhanced MRI before and three months after CIRT. The pre-treatment maximum standardized uptake value (SUVmax), and that three months after treatment, the difference between the pre- and post-CIRT SUVmax, the ratio of the post- to pre-SUVmax in FDG-PET and the size of the tumors were evaluated as predictors for local recurrence. FDG-PET and enhanced MRI were used to detect local recurrence.ResultsLocal recurrence appeared in 10 cases after CIRT. Nine of the 10 lesions (90.0 %) were detected with FDG-PET, while enhanced MRI detected just 50.0 % of the recurrences. One case of local recurrence, in which the lesion was negative on FDG-PET, was detected using enhanced MRI. A receiver operating characteristic curve analysis showed that neither the SUVmax on FDG-PET nor the tumor size before or three months after CIRT could be used to predict local recurrence.ConclusionsThe combination of FDG-PET and enhanced MRI is recommended to detect local recurrence for patients with sarcomas who have received CIRT; however, no parameters obtained during the examinations performed before and three months after CIRT accurately predicted the development of local recurrence.
Highlights
The results of treatment for malignant bone and soft-tissue tumors arising from the deep trunk and pelvis are still not acceptable due to the relatively high recurrence and low overall survival rates
13 patients were excluded because they did not receive pre- or post-treatment FDG-positron emission tomography (PET)/CT, three patients were excluded because chemotherapy was started within 1 month after carbon ion radiotherapy (CIRT), and this factor might affect the standardized uptake value (SUV) of fluoro-Dglucose positron emission tomography (FDG-PET), and two patients who were treated with postoperative CIRT were excluded because their tumors were not radiologically detected prior to treatment
All patients could receive FDG-PET/CT before CIRT and three months after CIRT, while two patients could not be examined with enhanced MRI because one had wires in the sternum near the lesions and one missed the examination three months after CIRT
Summary
The results of treatment for malignant bone and soft-tissue tumors arising from the deep trunk and pelvis are still not acceptable due to the relatively high recurrence and low overall survival rates. Carbon ion radiotherapy (CIRT) was applied for several malignancies, including bone and soft-tissue sarcomas, and provided favorable results. It has been unclear what modalities should be used for evaluating the response and for the follow-up of these patients. Our institute started performing carbon ion radiotherapy (CIRT) in 2010, and has treated various kinds of tumors, including sarcomas originating from the trunk and pelvis, for which surgical treatment is difficult or impossible [6]. Modalities that can precisely evaluate the tumor response after CIRT are required
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