Positron emission tomography (PET) was used in the follow-up of patients with colorectal malignancies to differentiate between recurrent colorectal tumor and scar. Patients were examined with oxygen-15-labeled water and with fluorine-18-labeled deoxyglucose (FDG). FDG was injected intravenously to assess tumor metabolism. The tracer concentration was quantitatively evaluated by means of a region-of-interest technique and standardized for both injected dose and body volume. Of 29 patients, 21 had recurrent colorectal malignancy, and eight had a nonmalignant mass. All malignancies were seen on the PET cross sections. Nonmalignant lesions had a low FDG accumulation on images obtained 60 minutes after injection. While the tumor-soft tissue ratio was highest shortly after the intravenous injection of FDG, the tumor-scar ratio was highest 60 minutes after injection. It was possible to differentiate tumor from non-malignant tissue with FDG with the use of standardized concentration values and tumor-soft tissue ratios. Imaging with O-15-labeled water gave no additional information.

Surgery is considered the treatment of choice for solitary brain lesions, and radiation therapy is indicated for metastases only in vital or sensitive regions that cannot be excised without risk of disabling neurologic defects. In these cases, radiosurgery may be an alternative to conventionally fractionated radiation therapy. At the Heidelberg linear accelerator‐based radiosurgery facility, 69 patients were treated for 102 inoperable brain metastases. The primary tumor sites included non‐small cell lung carcinoma (n = 24), renal cell carcinoma (n = 14), melanoma (skin) (n = 14), colorectal carcinoma (n = 6), carcinoma of unknown primary (n = 4), and others (n = 7). Eleven patients were treated for relapse after surgery or after conventional whole‐brain irradiation. The doses at the isocenter varied from 15–50 Gy (mean, 21.5 Gy). Ten patients with multiple metastases received a planned combination of whole‐brain irradiation plus a single boost of 15 Gy. The median survival time for the entire group was 6 months, with a 1‐year‐survival of 28.3%. Factors associated with significant improvement of survival were brain metastases without other metastatic disease and good response to radiation therapy. Five of 22 patients (22.9%) with metastases located only in the brain survived longer than 2 years. An improvement in neurologic function was found in 81% within a period of 3 months. With imaging techniques, complete remission was found in 20%, partial remission in 35%, stable disease in 40%, and relapse in 5%. The authors concluded that radiosurgery is an effective and safe therapy for brain metastases. It can be applied as primary treatment, as boost in combination with whole‐brain irradiation, or as treatment for patients with relapse in a previously irradiated field.

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Pharmacokinetic mapping of dynamic MR imaging data allows in vivo insight into tissue physiopathology, helping differentiate benign from malignant pelvic lesions in rectal cancer.

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Dose-escalated treatments, with particular regard to the inclusion or omission of TBI, should be prospectively investigated to find the best high-dose regimen.

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