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Biomedical subjects

C J Baines

Publications and source records attributed to C J Baines.

At least 55 records · Page 3Linked to original sources
PubMed1989

Physical examination. Its role as a single screening modality in the Canadian National Breast Screening Study.

Although often recommended as an important component in screening for breast cancer, physical examination of the breasts (PE) by medical professionals has not been well evaluated. The Canadian National Breast Screening Study (NBSS) permits estimation of sensitivity, specificity, and positive predictive value (PPV) of PE alone as performed by screen-examiners because 50% of the 89,835 NBSS participants did not receive mammography. There were 19,965 women aged from 50 to 59 years who were eligible to receive four or five annual PEs from 77 nurse-examiners, in 12 screen centers outside Quebec province and 58 physician-examiners in three screen centers in Quebec. The gold standard was histologically proven breast cancer. When a test was positive the participant was referred to the study surgeon for review. For screens one to five, sensitivity was 83, 71, 57, 83, and 77; specificity was 88, 94, 96, 96, and 96; and PPV was 3, 3, 4, 3, and 4, respectively. For 25,620 women aged 40 to 49 years who were eligible to receive only one PE, sensitivity was 71, specificity 84, and PPV 1.5. Using a binomial regression model, X2 for heterogeneity suggested there was no difference between nurse and physician examiners (P = 0.6879). Similar estimates made for the surgeons who performed 8914 reviews showed that sensitivity and PPV were higher than for the screen examiners and specificity was lower. These results support the conclusion that physical examination of the breasts by trained nurses is a useful component in screening for breast cancer.

Adult↗
PubMed1989

Cigarette smoking and breast cancer: case-control studies of prevalent and incident cancer in the Canadian National Breast Screening Study.

Two case-control studies of Canadian women aged 40-59 years are reported investigating the relation of cigarette smoking with initial visit (prevalent) and subsequent visit (incident) breast cancer detection, respectively, within the Canadian National Breast Screening Study. The analysis of prevalent breast cancer (1982-1985), which involved 254 cases and 762 controls, showed no evidence of an elevated risk for women with a history of cigarette smoking, with odds ratios of 0.9 (95% confidence interval (Cl) 0.6-1.5) and 1.2 (95% Cl 0.8-1.8) in premenopausal and postmenopausal subjects, respectively. Similarly, in the incident breast cancer analysis (1981-1987) based on 317 cases and 951 controls, women with a history of cigarette smoking had odds ratios of 1.2 (95% Cl 0.8-2.0) and 1.2 (95% Cl 0.9-1.7) in the premenopausal and postmenopausal categories, respectively. No evidence of dose response or of elevated risk in ex-smokers or current smokers was found in either study. These results persisted despite adjustment for several important variables. The present data demonstrate no association between smoking and prevalent or incident breast cancer in either menopausal category, contradicting the authors' previous finding of a positive association with premenopausal prevalent disease earlier in this screening study. The relation of smoking and breast cancer remains controversial. Further study is required to determine whether an association truly does not exist or whether smoking might have both protective and harmful effects that are mediated through different pathways, thus accounting for the paradoxical findings in the literature to date.

Adult↗
PubMed1988

Sensitivity and specificity of first screen mammography in 15 NBSS centres.

We report the sensitivity and specificity of first screen mammography in a 15-centre randomized screening trial. Of 44,718 women who received mammography and physical examination at first screening, 238 were diagnosed with breast cancer at first screen, 34 in the 12-month interval after the first screen, and 98 at the second screen. Seventeen of the interval cases and 47 of the second-year cancers were defined as potentially detectable at first screening. Interpretations of first screen mammograms by radiologists at the screening centres were matched to known histological outcomes. Simultaneous blind review of 2908 cases, which included all cancers detected at first and second screenings as well as interval cancers, was done by a single reference radiologist. The sensitivity of the technique as carried out at all NBSS centres was 0.75, the specificity 0.94, the positive predictive value 0.07, and the negative predictive value 0.998.

Breast Neoplasms↗
PubMed1988

Incentives for breast self-examination: role of the calendar.

Calendars are generally believed to be useful in promoting compliance with breast self-examination (BSE). To test this belief, calendars were distributed to 1,166 women in the Canadian National Breast Screening Study for comparison with 1,027 other participants who received no calendar. Recipients were asked to note their BSE findings each month on the calendar and to return calendars at the next annual screen. Self-reported BSE frequencies and BSE competence scores revealed no significant difference between the recipients and nonrecipients at three points in time: one year prior to, at time of, and one year after calendar distribution. Only 136 women returned calendars as requested. Their improvement in the test period did not differ significantly from that shown by the control group or the nonreturners. Calendars do not seem to be useful in a population receiving annual screening and BSE instruction.

Adult↗
PubMed1986

Changes in breast self-examination behavior in a cohort of 8214 women in the Canadian National Breast Screening Study.

A study cohort of 8214 women was formed from all participants in the Canadian National Breast Screening Study who attended their first three screens after the introduction of a structured evaluation protocol involving eight criteria for breast self-examination (BSE). Self-reported BSE frequency was collected by questionnaire at all three screens. Breast self-examination instruction preceded breast exam at each screen but BSE evaluation occurred only at the second and third screen. Reported monthly BSE frequency increased from 18% to 51% to 55% on first, second, and third screens, respectively. The proportion claiming to do no BSE fell correspondingly: 52%, 16%, and 11%. Compliance with each of the seven other BSE criteria was significantly greater at the third screen than at the second. The mean number of these criteria performed at screen 3 was 5.1 compared with 4.4 at screen 2; older women performed as well as younger. The mean number of criteria performed was associated with BSE frequency at screen 3. The authors conclude that women's BSE behavior can be altered, and that integration of BSE evaluation and instruction into routine medical exams seems feasible and potentially useful.

Adult↗
PubMed1986

Selection of women at high risk of breast cancer for initial screening.

Selective breast cancer screening refers to the intentional restriction of screening to only a high-risk subgroup of the total population of women at risk. Using data from the Canadian National Breast Screening Study, we explored methods of defining such subgroups. Discriminants were based on risk factor information collected prior to screening and were constructed using a training group of 77 cases and 400 controls. They were then tested on a separate group of 38 cases and 200 controls. Both simple risk factor counts and logistic models were utilized and separate analyses were performed for pre- and post-menopausal women. Using a logistic model, we were able to define a high-risk subgroup encompassing less than 40% of the test controls and over 85% of the test cases. Such a selection strategy, if implemented, might reduce initial visit mammography rates by up to 60% with only a small reduction in case detection. Other uses as determining the optimal age for initiation of screening are also discussed.

Age Factors↗
PubMed1986

Sensitivity and specificity of first screen mammography in the Canadian National Breast Screening Study: a preliminary report from five centers.

Sensitivity and specificity of first screen mammography in a randomized screening trial at five centers are reported. A total of 23,101 women underwent mammography; in 139, breast cancer was detected at first screening; in 20, less than 12 months after first screening; and in 47, at second screening. All 206 cancer cases were histologically confirmed, and 174 were defined as being detectable at first screening. Average length of follow-up for all women was 3.2 years. Interpretations of first screen mammograms by the center radiologists were matched to known outcomes. Simultaneous blind review was performed by a single reference radiologist with mammograms from all 206 cancer cases and those of a random sample of 739 women not known to have breast cancer at 15 months or more after initial screening. Overall, the five screening centers achieved a sensitivity of 69% (range, 60%-78%), a specificity of 94% (range, 93%-96%), a positive predictive value of 8.6% (range, 3%-16%), and a negative predictive value of 99.7% (range, 99.6%-99.9%).

Breast Neoplasms↗
PubMed1986

Audit procedures in the National Breast Screening Study: mammography interpretation.

Audit procedures for mammography interpretation in a national breast cancer screening program are described. Agreement between radiologists at five screening centers and a single reference radiologist was evaluated based on mammograms at initial screen in 739 women not known to have breast cancer and 204 breast cancer cases detected at or within a year of initial screen. Kappa statistics, used to measure agreement in the interpretation of mammograms between the reference and center radiologists beyond that attributable to chance, were 0.409 in women not known to have breast cancer, 0.472 in women with diagnosed breast cancer, and 0.493 for all women with p less than .0001 for all three categories. To our knowledge, this is the first report presenting measures of agreement made systematically, simultaneously, and on a continuing basis, during a screening program for quality assurance.

Adult↗
PubMed1984

Impediments to recruitment in the Canadian National Breast Screening Study: response and resolution.

Eighteen months after the 1980 initiation of the Canadian National Breast Screening Study (NBSS) (a multicenter randomized controlled trial that will involve 90,000 women), the Toronto center experience such severe problems with recruitment that the study as a whole was jeopardized. Impediments to recruitment arose in five areas. The design of the protocol was criticized by some physicians and participants, a problem that could only be met by justifying the design. A second problem was a lack of understanding of the concept of screening and mistaken assumptions about what participation in the NBSS entailed. Thirdly, recruitment problems occurred at a time when the media were focusing much attention on the hazards of low-level ionizing radiation. Fourthly, women were found to have a variety of personal reasons for delaying or avoiding entry into the study. Finally, factors characteristic of the Canadian milieu such as universal health coverage may have acted as a disincentive to entry. To improve physician understanding, NBSS personnel made presentations at medical rounds and scientific meetings; articles were written for medical journals. To win support from the lay public, talks were given to recreation or work-based groups. Appearances on radio and television talk shows were sought out. Mass mailings to university staff and professional associations did not produce large responses, nor did advertisements on television, radio, or in newspapers. The distribution of a check insert in a government mailing gave rise to hundreds of appointments across Canada. However, for generating an ongoing adequate level of recruitment, the best measure has been the mailing of personally addressed letters to eligible women followed by a telephone call. Data on response rates, cost and women's attitudes toward the study are reported. By early 1983, Toronto met its recruitment target of 12,000.

Adult↗