Is a 3-mm intrafractional margin sufficient for daily image-guided intensity-modulated radiation therapy of prostate cancer?

PURPOSE: To determine whether a 3-mm isotropic target margin adequately covers the prostate and seminal vesicles (SVs) during administration of an intensity-modulated radiation therapy (IMRT) treatment fraction, assuming that daily image-guided setup is performed just before each fraction. MATERIALS AND METHODS: In-room computed tomographic (CT) scans were acquired immediately before and after a daily treatment fraction in 46 patients with prostate cancer. An eight-field IMRT plan was designed using the pre-fraction CT with a 3-mm margin and subsequently recalculated on the post-fraction CT. For convenience of comparison, dose plans were scaled to full course of treatment (75.6 Gy). Dose coverage was assessed on the post-treatment CT image set. RESULTS: During one treatment fraction (21.4+/-5.5 min), there were reductions in the volumes of the prostate and SVs receiving the prescribed dose (median reduction 0.1% and 1.0%, respectively, p<0.001) and in the minimum dose to 0.1 cm(3) of their volumes (median reduction 0.5 and 1.5 Gy, p<0.001). Of the 46 patients, three patients' prostates and eight patients' SVs did not maintain dose coverage above 70 Gy. Rectal filling correlated with decreased percentage-volume of SV receiving 75.6, 70, and 60 Gy (p<0.02). CONCLUSIONS: The 3-mm intrafractional margin was adequate for prostate dose coverage. However, a significant subset of patients lost SV dose coverage. The rectal volume change significantly affected SV dose coverage. For advanced-stage prostate cancers, we recommend to use larger margins or improve organ immobilization (such as with a rectal balloon) to ensure SV coverage.

A STUDY OF THE ATTITUDES OF ELDERLY CONSUMERS TOWARD DENTAL CARE AND ORAL HEALTH

This paper describes a study of the attitudes of elderly consumers toward dental care and oral health. Four hundred and two respondents ages 60-97 were interviewed with a 62 item questionnaire. Attitudes were measured regarding: quality of care, sufficient utilization of care, priority of oral health, patient-provider interaction, individual control over health, powerful others control of health, and chance as the locus of control over health. Analysis of variance was performed on the sample of males and females separately. Fifty-four hypotheses were tested on each sex. Race and self-concept were excellent predictors of attitude for both sexes and SES (socioeconomic status) and self-reported health were good predictors for females. There was no statistically significant relationship between the frequency with which the elderly utilize dental care and their attitudes toward the quality of care they receive. Foremost reason for non-utilization was that of no felt need. Those selecting this reason were likely to be Anglo females, wearers of dentures, in good health. Those selecting cost as the foremost reason for non-utilization were Black, in fair health, of either sex, missing some teeth, but with no dentures. Overall attitudes toward quality of dental care were positive, despite the fact that this group was exposed to dental care in its infancy. This may suggest that the elderly recognize the importance of technological advances in dentistry. Women with low income and education levels were more likely to have positive attitudes about quality of care than other females. Attitudes about interaction between patient and provider were overall negative. The sample scored high on individual control over health, and scored lower, but nonetheless positively, on feelings that persons other than themselves are most essential to maintaining health. Overall these elderly persons did not agree that they relied on chance in matters of health. Those who did choose this locus were female, with lower SES and health status. Though males scored high on internal control of health, those with lowest scores were Mexican-American or had never been married. Sex and ethnicity were the best predictors of attitude across all measures in the study.^