We previously reported aggregate data showing that PET was associated with a change in intended management for over one third of patients participating in the National Oncologic PET Registry (NOPR). Here, we present results for specific cancer types and indications for testing. Methods: The NOPR collected questionnaire data from referring physicians on intended management before and after PET. Data were available from 40,863 PET studies done at 1,368 centers. The impact of PET was assessed for 18 cancer types in patients with pathologically confirmed cancer by type and indication for testing (initial staging, restaging, or detection of suspected recurrence), other than treatment monitoring. Results: When intended management was classified as treatment or nontreatment, physicians changed their intended management for 38.0% of cases (95% confidence interval 5 37.6%238.5%). The frequencies of changes in management ranged from 48.7% for myeloma to 31.4% for nonmelanoma skin cancer. Comparisons across testing indications revealed that only in multiple myeloma did PET have a consistently greater impact on intended management. When the intended management plan before PET was treatment, a change in the intent of treatment (curative vs. palliative) or a major change in the modality of treatment occurred at similar frequencies across different cancer types. Conclusion: The impact of PET on physicians' intended management for patients with known cancer was consistent across cancer types.

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Absorptiometric procedures are described for the determination of niobium and tantalum in mixtures of their oxides. The method is applied to the determination of the two metals in mixtures obtained by their chromatographic extraction from minerals and ores. The determinations depend on the formation of a coloured complex between tantalum and pyrogallol in acid solution and between niobium and pyrogallol in alkaline solution. Both systems obey Beer's law, and, with 1-cm cells, the optimum limits of concentration are 0 to 20 p.p.m. for niobium and 0 to 80 p.p.m. for tantalum. The effect of variation in pH and the interference of a number of cations and anions are recorded.

Rapid and simple methods are described for the determination of copper, cobalt, nickel, niobium, tantalum, lead and uranium in soil samples. Following the breakdown of the samples and dissolution of the trace metals by methods applicable in the field, the trace metal or metals are separated chromatographically by apward 'diffusion of a solvent on slotted sheets of paper which enable ten separations to be performed simultaneously. The metals are detected by spraying the strips with suitable reagents and the amount present is determined b,y visual comparison with standards. Copper, cobalt and nickel are determined after a single separation. The same soil extract is used for the determination of both niobium and tantalum. This type of prospecting is rapidly growing in popularity and importance. March, 19551 METHODS OF ANALYSIS TO GEOCHEMICAL PROSPECTING 173 * Uranium determined colorirnetrically.

An improved and more sensitive method is described for the determination of carbon disulphide vapour in air a t concentrations up to 40 p.p.m. V / V . Carbon disulphide vapour is absorbed from a 500-ml sample of air into an ethanolic solution containing copper(I1) acetate, diethylamine and triethanolamine. The yellow colour produced is compared visually with standard colours or measured spectrophotometrically. For field use, the apparatus is portable and simple to operate, and requires a working time of about 5 minutes per determination.THE field test currently in use by H.M. Factory Inspectorate for the determination of carbon disulphide vapour in air1 is basically the same as that which was first published in 1939 and is derived from a method2 originally published in 1932. The method is required for assessing the atmosphere within a factory and to give a rapid, approximate determination of concentrations of carbon disulphide in the region of the threshold limit value, currently 20 p.p.m. V / V , 3 in order to judge whether or not a hazard to health exists. (Threshold limit values refer to time-weighted concentrations in air for an 8-hour working day and a 40-hour working week, and represent conditions under which it is believed that nearly all workers may be repeatedly exposed without adverse effect on their health. Detailed conditions and exceptions are given in reference 3.) A re-examination of the method was undertaken for the following three reasons.(i) It was occasionally found that when the component solutions were mixed in the bubbler the absorption solution became turbid and its colour blue instead of remaining a clear, pale green. (ii)The volume of air to be sampled (2.5 litres) was of an inconvenient size; it was excessively large for the use of a rubber-bulb aspirator, which would require twenty aspirations, and too small to warrant the use of an electric pump and flow meter. The rubber-bulb aspirator was preferred because of its portability, and so an increase in sensitivity was sought in order to permit a reduction in the volume of air sampled. (iiz)The existing method was devised before threshold limit values for toxic substances in air were first compiled and it does not provide for a standard at the threshold limit value for carbon disulphide.A survey of published analytical methods disclosed no method that appeared suitable for adaptation as a replacement for the existing method, and modification of the latter seemed to afford the most profitable line of investigation.