Follow-up of hepatic and peritoneal metastases of gastrointestinal tumors (GIST) under Imatinib therapy requires different criteria of radiological evaluation (size is not everything!!!).

PURPOSE: To define computed tomography (CT) criteria for evaluating the response of patients with gastrointestinal stromal tumors (GIST) who are receiving Imatinib (tyrosine-kinase inhibitor therapy). MATERIALS AND METHODS: This prospective CT study evaluated 107 consecutive patients with advanced metastatic GIST treated with Imatinib. RESULTS: Seventy patients had total or partial cystic-like transformation of hepatic and/or peritoneal metastases. These pseudocysts remained unchanged in size or stable in size on successive CT examinations (stable disease according to RECIST criteria). Forty-six patients developed metastases, 17 patients showed increasing parietal thickness and 29 patients with peripheral enhancing nodules. These CT changes represented local recurrence consistent with GIST resistance to Imatinib treatment. WHO or RECIST criteria did not provide a reliable evaluation of disease evolution or recurrence. Development of new enhancement of lesions (parietal thickness or nodule) was the only reliable criterion. CONCLUSION: The development of peripheral thickening or enhancing nodules within cystic-like metastatic lesions, even without any change in size, represented progressive GIST under Imatinib, growing in a short time and should alert the clinician for the possible need for a change in therapy.

Role of computed tomography in the follow-up of hepatic and peritoneal metastases of GIST under imatinib mesylate treatment: a prospective study of 54 patients.

PURPOSE: To prospectively analyze the evolution of hepatic and peritoneal unresectable metastases from gastrointestinal stromal tumors (GIST) under imatinib mesylate, a new targeted treatment, which induces changes in lesion structure. MATERIALS AND METHODS: 54 patients with metastases from GIST underwent an abdominal and pelvic computed tomography examination without and with contrast enhancement, before and during treatment with imatinib mesylate. The number and size of lesions and contrast enhancement were noted before treatment and every 2 weeks for the first 2 months, then every 2 months for the first year of treatment and every 3 months thereafter. RESULTS: 27 patients presented with both hepatic and peritoneal metastases, 14 had only peritoneal and 13, only hepatic disease. On baseline imaging, all metastases were hypodense heterogeneous lesions with progressive, concentric enhancement. After treatment (mean duration of follow-up: 23 months) metastases decreased in size number and enhancement in 35/54 patients, remained stable in 2 patients and increased in 14 patients. In 13/39 patients with hepatic metastases a cyst-like appearance was noted. Reactivation after a partial response appeared first as a focal, peripheral, solid nodule in the wall of a cystic lesion, or an increase in lesion density, before size regrew. CONCLUSION: Besides the classic size criterion, a decrease in density and in contrast enhancement with stable "near cystic" lesions signifies a good response. A more aggressive approach (surgery or radiofrequency ablation) may be indicated for initially focal recurrences with a stable size.

Fast magnetic resonance imaging with contrast for soft tissue sarcoma viability.

Because dynamic (fast) contrast-enhanced magnetic resonance imaging with its temporal resolution allows evaluation of contrast kinetics of soft tissue sarcomas, its efficacy for defining viable tumor in these neoplasms was studied for three applications: biopsy localization, chemotherapeutic response, and differentiation between recurrence and inflammation after treatment. After conventional T1-weighted and T2-weighted magnetic resonance sequences to localize the lesion, patients had dynamic contrast-enhanced magnetic resonance imaging with fast and ultrafast sequences and postprocessing techniques (subtraction, time-intensity curves, and parametric color-encoding). In 10 of 40 patients, dynamic imaging more precisely defined the most malignant foci of tumor for biopsy than conventional magnetic resonance imaging. After chemotherapy, dynamic imaging distinguished 11 good responders from 21 poor responders. In followup of 196 patients, dynamic imaging detected 42 early enhancing recurrences and excluded recurrent tumor in six late enhancing pseudotumors. Dynamic imaging can differentiate viable tumor from nonviable tumor and inflammation by showing two temporally different phases of contrast enhancement: an early phase correlative with viable tumor at histologic examination, and a late phase when all tissues enhance simultaneously and may be indistinguishable. By showing tumor viability, dynamic contrast-enhanced magnetic resonance imaging can help define biopsy sites, chemotherapeutic response, and presence or absence of recurrences and therefore affect the initial evaluation, treatment, and followup of patients with soft tissue sarcomas.

Dynamic Contrast-Enhanced MR Imaging for Soft Tissue Sarcomas.

Dynamic contrast-enhanced magnetic resonance imaging has recently emerged as an important method for evaluating soft tissue sarcomas for biopsy localization, chemotherapeutic response, and long-term follow-up because of its ability to detect viable tumor. This article presents the basic principles of contrast kinetics in soft tissue sarcomas after bolus injection of contrast agent and discusses the current postprocessing methods (subtraction, first-pass image and time-intensity curves with region of interest, and color-encoded techniques) used to display these dynamic studies. Because of its excellent temporal resolution, dynamic MR imaging can delineate the early uptake of contrast agent in sarcomas within seconds after injection, almost synchronous with arterial enhancement, and thereby differentiate the rapidly enhancing viable tumor from the nonenhancing necrotic tumor and the late enhancing changes after surgery, radiation therapy, and chemotherapy.

MR Imaging in the Follow-Up Evaluation of Aggressive Soft Tissue Tumors.

Although newer imaging techniques aid in the diagnosis of soft tissue sarcomas and current surgical procedures and adjunct therapy decrease the incidence of their recurrences when patients are referred to oncologic centers, the majority of these tumors are suboptimally evaluated in general practice with frequent recurrences. Close surveillance of these patients is necessary for early recognition and treatment of recurrent disease. This article describes an organized, stepwise magnetic resonance imaging evaluation of these patients after surgery and radiation therapy. The initial sequence should be T2-weighted. Low signal intensity or diffuse high signal intensity without mass on T2-weighted sequence excludes recurrence in 99% of patients. A high signal intensity mass, however, should be studied with bolus injection of contrast medium. Although standard contrast-enhanced MR imaging differentiates the non-enhancing hygroma or hematoma from the enhancing recurrence or pseudotumor, dynamic contrast-enhanced MR imaging is required to distinguish the rapidly enhancing recurrent tumor from the slowly enhancing pseudotumor of inflammation.

An Algorithm for Soft Tissue Tumors: Current Perspectives.

The diagnosis and treatment of soft tissue sarcomas has dramatically changed in the last 10 to 15 years with more precise preoperative diagnosis, resection, adjunct therapy, and long-term follow-up. With correct preoperative diagnosis and staging of a soft tissue sarcoma, the surgeon, in conjunction with the radiation therapist and the medical oncologist, can select the optimal therapeutic approach to minimize the development of recurrences and metastases. Recognition of a mass as benign or non-neoplastic prevents unnecessary surgery. This article presents an algorithm that demonstrates the important interactions and contributions of the various oncologic-related disciplines (surgery, radiology, pathology, medical oncology, and radiation therapy) to the care of patients with soft tissue tumors.