Comparison of IMRT techniques in the radiotherapeutic management of head and neck cancer: is tomotherapy "better" than step-and-shoot IMRT?

Currently, the most common method of delivering intensity-modulated radiotherapy (IMRT) is through step-and-shoot, segmental multi-leaf collimator (SMLC)-based techniques. Although rotational delivery methods such as helical tomotherapy (HT) have been proposed as offering advantages in the treatment of head and neck cancer, a lack of clinical data exists on its potential utility. This study compared dosimetric, clinical, and quality-of-life endpoints among 149 patients treated by HT and SMLC-IMRT for head and neck cancer. Dosimetric analysis revealed that the use of HT resulted in significant improvements with respect to mean dose (23.5 versus 27.9 Gy, p = 0.03) and V30 (30.1 versus 43.9 Gy, p = 0.01) to the contralateral (spared) parotid gland. However, the incidence of grade 3+ xerostomia in the late setting was 10% and 8% among patients treated by HT and SMLC-IMRT, respectively (p = 0.46). There were no significant differences in any of the quality of life endpoints among patients treated by HT and SMLC-IMRT (p > 0.05, for all). Acknowledging the biases inherent in this retrospective analysis, we found that the dosimetric advantages observed with HT compared to SMLC-IMRT failed to translate into significant improvements in clinical outcome. Prospective studies are needed to further evaluate how HT may affect the therapeutic ratio.

Organic carbon-14 in the Amazon river system.

Coarse and fine suspended particulate organic materials and dissolved humic and fulvic acids transported by the Amazon River all contain bomb-produced carbon-14, indicating relatively rapid turnover of the parent carbon pools. However, the carbon-14 contents of these coexisting carbon forms are measurably different and may reflect varying degrees of retention by soils in the drainage basin.

Clinical observations on Babesia gibsoni and Babesia canis infections in dogs.

Thirty-five cases of Babesia gibsoni infection and 11 cases of Babesia canis infection were diagnosed and treated in dogs at Kadena Air Base in Okinawa, Japan, between April 1979 and February 1980. Diagnosis was made by demonstrating the organisms in blood smears and by serologic examination, using an indirect fluorescent antibody test. Serologic findings correlated well with the occurrence of infection in mature dogs, but poorly in young (1- to 3-month-old) dogs. Although these 2 intraerythrocytic parasites were readily distinguishable on Giemsa-stained blood smears and by the indirect fluorescent antibody test, the clinical syndromes were similar. Most dogs were anorectic and depressed and were found to have regenerative anemia. Of 37 dogs tested, 31 were Coomb's test-positive, and most of these became Coombs' test-negative after treatment and disappearance of clinical signs. Specific treatment consisted predominantly of the use of diminazene aceturate. Pentamidine isethionate also used. Although these drugs were effective in halting and reversing the clinical progression of the disease, they usually were ineffective in clearing the blood of B gibsoni organisms, and relapses commonly occurred. Both drugs appeared to be more effective against B canis. It was concluded that some of the several hundred dogs arriving in the United States annually from Okinawa are carriers of B gibsoni, a parasite only recently discovered in North America.

A method for characterizing subgroups and related survivals in cancer patients. Application to brain tumors.

It has long been known that if the probability of dying of a given cancer remains constant over time, the logarithmic plot of survival of a group of patients with that cancer will be a straight line. More frequently, however, the probability of dying varies with time and the logarithmic survival plot is a curve. We believe that in some cases a population of patients with one type of neoplasm may be composed of several subgroups, each of which has a simple predictable course with a rectilinear survival plot. This article describes a method for partitioning such survival plots and identifying and characterizing the subgroups and applies the method to a group of patients with brain tumors. The value of being able to identify these subgroups and their relative proportions, the observations that can be made with this analysis regarding the nature of the various subgroups of brain tumors, and the implications of changes in the half-lives as well as the proportions of the subgroups with time are discussed.