The OncoSim model: development and use for better decision-making in Canadian cancer control

The Canadian Partnership Against Cancer was created in 2007 by the federal government to accelerate cancer control across Canada. Its OncoSim microsimulation model platform, which consists of a suite of specific cancer models, was conceived as a tool to augment conventional resources for population-level policy- and decision-making. The Canadian Partnership Against Cancer manages the OncoSim program, with funding from Health Canada and model development by Statistics Canada. Microsimulation modelling allows for the detailed capture of population heterogeneity and health and demographic history over time. Extensive data from multiple Canadian sources were used as inputs or to validate the model. OncoSim has been validated through expert consultation; assessments of face validity, internal validity, and external validity; and model fit against observed data. The platform comprises three in-depth cancer models (lung, colorectal, cervical), with another in-depth model (breast) and a generalized model (25 cancers) being in development. Unique among models of its class, OncoSim is available online for public sector use free of charge. Users can customize input values and output display, and extensive user support is provided. OncoSim has been used to support decision-making at the national and jurisdictional levels. Although simulation studies are generally not included in hierarchies of evidence, they are integral to informing cancer control policy when clinical studies are not feasible. OncoSim can evaluate complex intervention scenarios for multiple cancers. Canadian decision-makers thus have a powerful tool to assess the costs, benefits, cost-effectiveness, and budgetary effects of cancer control interventions when faced with difficult choices for improvements in population health and resource allocation.

Using the Cancer Risk Management Model to evaluate the health and economic impacts of cytology compared with human papillomavirus DNA testing for primary cervical cancer screening in Canada

BACKGROUND

In Canada, discussion about changing from cytology to human papillomavirus (hpv) dna testing for primary screening in cervical cancer is ongoing. However, the Canadian Task Force on Preventive Health Care has not yet made a recommendation, concluding that the evidence is insufficient.

METHODS

We used the cervical cancer and hpv transmission models of the Cancer Risk Management Model to study the health and economic outcomes of primary cytology compared with hpv dna testing in 14 screening scenarios with varying screening modalities and intervals. Projected cervical cancer cases, deaths, colposcopies, screens, costs, and incremental cost-effectiveness were evaluated. We performed sensitivity analyses for hpv dna test costs.

RESULTS

Compared with triennial cytology from age 25, 5-yearly hpv dna screening alone from age 30 resulted in equivalent incident cases and deaths, but 55% (82,000) fewer colposcopies and 43% (1,195,000) fewer screens. At hpv dna screening intervals of 3 years, whether alone or in an age-based sequence with cytology, screening costs are greater, but at intervals of more than 5 years, they are lower. Scenarios on the cost-effectiveness frontier were hpv dna testing alone every 10, 7.5, 5, or 3 years, and triennial cytology starting at age 21 or 25 when combined with hpv dna testing every 3 years.

CONCLUSIONS

Changing from cytology to hpv dna testing as the primary screening test for cervical cancer would be an acceptable strategy in Canada with respect to incidence, mortality, screening and diagnostic test volumes.

Using the Cancer Risk Management Model to evaluate colorectal cancer screening options for Canada

BACKGROUND

Several screening methods for colorectal cancer (crc) are available, and some have been shown by randomized trials to be effective. In the present study, we used a well-developed population health simulation model to compare the risks and benefits of a variety of screening scenarios. Tests considered were the fecal occult blood test (fobt), the fecal immunochemical test (fit), flexible sigmoidoscopy, and colonoscopy. Outcomes considered included years of life gained, crc cases and deaths prevented, and direct health system costs.

METHODS

A natural history model of crc was implemented and calibrated to specified targets within the framework of the Cancer Risk Management Model (crmm) from the Canadian Partnership Against Cancer. The crmm-crc permits users to enter their own parameter values or to use program-specified base values. For each of 23 screening scenarios, we used the crmm-crc to run 10 million replicate simulations.

RESULTS

Using base parameter values and some user-specified values in the crmm-crc, and comparing our screening scenarios with no screening, all screening scenarios were found to reduce the incidence of and mortality from crc. The fobt was the least effective test; it was not associated with lower net cost. Colonoscopy screening was the most effective test; it had net costs comparable to those for several other strategies considered, but required more than 3 times the colonoscopy resources needed by other approaches. After colonoscopy, strategies based on the fit were predicted to be the most effective. In sensitivity analyses performed for the fobt and fit screening strategies, fobt parameter values associated with high-sensitivity formulations were associated with a substantial increase in test effectiveness. The fit was more cost-effective at the 50 ng/mL threshold than at the 100 ng/mL threshold.

CONCLUSIONS

The crmm-crc provides a sophisticated and flexible environment in which to evaluate crc control options. All screening scenarios considered in this study effectively reduced crc mortality, although sensitivity analyses demonstrated some uncertainty in the magnitude of the improvements. Where possible, local data should be used to reduce uncertainty in the parameters.

Comparison of 1- and 2-year screening intervals for women undergoing screening mammography

We compared the long-term impact of 1- and 2-year screening mammography intervals using prognostic, screening, and outcome information for women aged 50–74 years obtained from the Screening Mammography Program of British Columbia in two time periods, prior to 1997 (policy of annual mammography) and after 1997 (biennial mammography). Survival was estimated for both periods using a prognostic model and the expected rate of interval and screen-detected cancers. The likelihood of a screen-detected cancer with annual screening was 2.32 per thousand screens and with biennial screening was 3.32 per thousand screens. The prognostic profile of screen-detected cancers was better than that of interval cancers. Among both screen-detected and interval cancers, the prognostic profiles with annual and biennial screening were similar. The estimated breast cancer-specific survival rates for women undergoing annual and biennial screening mammography were 95.2 and 94.6% at 5 years, and 90.4 and 89.2% at 10 years, respectively. Annual compared to biennial mammography was associated with a 1.2% increase in the estimated 10-year breast cancer-specific survival for women aged 50–74 years, diagnosed with invasive breast cancer after screening programme attendance.

The effect of heterogeneity on optimal regimens in cancer chemotherapy

Optimal drug regimens for cancer chemotherapy are determined when knowledge is only available on the behaviour of the tumour and the drugs used, over a population of patients. The case of two drugs is investigated where they are equivalent on average. Our calculations indicate that the optimal regimen has both drugs given initially but then sequences the two drugs. Our calculations also indicate that as tumour heterogeneity increases, the benefit to be gained from the optimal regimen can decrease in comparison to reasonable regimens. This has the effect of complicating the calculation of optimal regimens in a clinical setting, and may explain why results in experimental oncology fail to carry over to clinical oncology.

Alcohol, tobacco and breast cancer--collaborative reanalysis of individual data from 53 epidemiological studies, including 58,515 women with breast cancer and 95,067 women without the disease

Alcohol and tobacco consumption are closely correlated and published results on their association with breast cancer have not always allowed adequately for confounding between these exposures. Over 80% of the relevant information worldwide on alcohol and tobacco consumption and breast cancer were collated, checked and analysed centrally. Analyses included 58,515 women with invasive breast cancer and 95,067 controls from 53 studies. Relative risks of breast cancer were estimated, after stratifying by study, age, parity and, where appropriate, women's age when their first child was born and consumption of alcohol and tobacco. The average consumption of alcohol reported by controls from developed countries was 6.0 g per day, i.e. about half a unit/drink of alcohol per day, and was greater in ever-smokers than never-smokers, (8.4 g per day and 5.0 g per day, respectively). Compared with women who reported drinking no alcohol, the relative risk of breast cancer was 1.32 (1.19-1.45, P<0.00001) for an intake of 35-44 g per day alcohol, and 1.46 (1.33-1.61, P<0.00001) for >/=45 g per day alcohol. The relative risk of breast cancer increased by 7.1% (95% CI 5.5-8.7%; P<0.00001) for each additional 10 g per day intake of alcohol, i.e. for each extra unit or drink of alcohol consumed on a daily basis. This increase was the same in ever-smokers and never-smokers (7.1% per 10 g per day, P<0.00001, in each group). By contrast, the relationship between smoking and breast cancer was substantially confounded by the effect of alcohol. When analyses were restricted to 22 255 women with breast cancer and 40 832 controls who reported drinking no alcohol, smoking was not associated with breast cancer (compared to never-smokers, relative risk for ever-smokers=1.03, 95% CI 0.98-1.07, and for current smokers=0.99, 0.92-1.05). The results for alcohol and for tobacco did not vary substantially across studies, study designs, or according to 15 personal characteristics of the women; nor were the findings materially confounded by any of these factors. If the observed relationship for alcohol is causal, these results suggest that about 4% of the breast cancers in developed countries are attributable to alcohol. In developing countries, where alcohol consumption among controls averaged only 0.4 g per day, alcohol would have a negligible effect on the incidence of breast cancer. In conclusion, smoking has little or no independent effect on the risk of developing breast cancer; the effect of alcohol on breast cancer needs to be interpreted in the context of its beneficial effects, in moderation, on cardiovascular disease and its harmful effects on cirrhosis and cancers of the mouth, larynx, oesophagus and liver.

Improving the time to diagnosis after an abnormal screening mammogram

INTRODUCTION

Five community-specific interventions to reduce the time to diagnosis after an abnormal breast screen have been evaluated.

METHODS

Subjects with abnormal screening mammograms in 1998 were assessed through five community pilot projects (N = 1137) and a control random sample assessed elsewhere in BC (N = 1053). The number, types, dates and physician costs of breast-related interventions after an abnormal screen were compared between pilots and control.

RESULTS

The median time to diagnosis for women without a biopsy was reduced from 23 days to 7 days (p = 0.001) in the pilot with facilitated referral to diagnosis. The median time to diagnosis for women with a biopsy was reduced from 57 days to 22-43 days in the pilots. Median physician costs per subject were lower (p = 0.02) in pilots that more frequently used core biopsy to obtain a diagnosis.

CONCLUSIONS

Process changes can improve the time to diagnosis after an abnormal breast screen, with similar or lower physician costs per subject. Facilitating the referral process had the greatest impact.

Optimal control for a stochastic model of cancer chemotherapy

Chemotherapy is useful in a number of cancers to reduce or eliminate residual disease. When used in this way the objective is to maximise the likelihood that the cancer will be eliminated. In this article, we extend a stochastic model of chemotherapy for cancer to incorporate its concomitant effect on the normal system and derive overall measures of outcome. The model includes the development of drug resistance and is sufficiently flexible to include a variety of tumour and normal system growth functions. The model is then applied to situations previously examined in the literature and it is shown that early intensification is a common feature of successful regimens in situations where drug resistance is likely. The model is also applied to data collected from clinical trials analysing the effect of adriamycin, and cyclophosphamide, methotrexate and 5-flourouracil (CMF) therapy in the treatment of operable breast cancer. The model is able to mimic the data and provides a description of the optimal regimen.

Broad-spectrum sunscreen use and the development of new nevi in white children: A randomized controlled trial

CONTEXT

High nevus density is a risk factor for cutaneous malignant melanoma. Melanocytic nevi originate in childhood and are largely caused by solar exposure.

OBJECTIVE

To determine whether use of broad-spectrum, high-sun protection factor (SPF) sunscreen attenuates development of nevi in white children.

DESIGN

Randomized trial conducted June 1993 to May 1996.

SETTING AND PARTICIPANTS

A total of 458 Vancouver, British Columbia, schoolchildren in grades 1 and 4 were randomized in 1993. After exclusion of nonwhite children and those lost to follow-up or with missing data, 309 children remained for analysis. Each child's nevi were enumerated at the start and end of the study in 1996.

INTERVENTION

Parents of children randomly assigned to the treatment group (n=222) received a supply of SPF 30 broad-spectrum sunscreen with directions to apply it to exposed sites when the child was expected to be in the sun for 30 minutes or more. Children randomly assigned to the control group (n=236) received no sunscreen and were given no advice about sunscreen use.

MAIN OUTCOME MEASURE

Number of new nevi acquired during the 3 years of the study, compared between treatment and control groups.

RESULTS

Children in the sunscreen group developed fewer nevi than did children in the control group (median counts, 24 vs 28; P=.048). A significant interaction was detected between freckling and study group, indicating that sunscreen use was much more important for children with freckles than for children without. Modeling of the data suggests that freckled children assigned to a broad-spectrum sunscreen intervention would develop 30% to 40% fewer new nevi than freckled children assigned to the control group.

CONCLUSIONS

Our data indicate that broad-spectrum sunscreens may attenuate the number of nevi in white children, especially if they have freckles. JAMA. 2000.

Standardized abnormal interpretation and cancer detection ratios to assess reading volume and reader performance in a breast screening program

PURPOSE

To determine the relationship between annual screening volume and radiologist performance in the Screening Mammography Program of British Columbia, Canada.

MATERIALS AND METHODS

Standardized abnormal interpretation ratios and standardized cancer detection ratios were constructed for 35 readers with at least 3 years of experience with the Screening Mammography Program of British Columbia. The ratios were used to compare individual reader performance with the mean program performance after adjustment for the age and screening history (first versus subsequent screening examinations) of the women who underwent screening.

RESULTS

The mean standardized abnormal interpretation ratio was better for readers of 2,000-2,999 (n = 8) and 3,000-3,999 (n = 9) screening mammograms per year than for those of less than 2,000 (n = 9) and 4, 000-5,199 (n = 9) screening mammograms per year. Differences in the mean standardized abnormal interpretation ratios were significant (P <.05) between the readers of less than 2,000 and of 2,000-2,999 screening mammograms per year, between readers of less than 2,000 and of 3,000-3,999 screening mammograms per year and between readers of 3,000-3,999 and of 4,000-5,199 screening mammograms per year. The mean standardized cancer detection ratio improved gradually with increasing annual volume, but the differences between groups were not statistically significant. Five of the eight readers of 2,000-2, 999 mammograms were reading 2,475 or more screening mammograms per year.

CONCLUSION

Standardized abnormal interpretation ratios and standardized cancer detection ratios provide a method of comparing two important performance measures in a screening program. A minimum of 2,500 interpretations per year is associated with lower abnormal interpretation rates and average or better cancer detection rates.

Pion conformal radiation of prostate cancer: results of a randomized study

PURPOSE

To compare the efficacy of pion radiation therapy with conventional external beam photon therapy, for the treatment of locally advanced stage T3/4, N0, M0 adenocarcinoma of the prostate.

METHODS AND MATERIALS

Two hundred seventeen eligible patients were randomly allocated to either photon or pion therapy. No adjuvant hormone therapy was used.

RESULTS

Median follow-up was 42 months (range 2-90). Acute bladder toxicity was worse in the pion arm, p = 0.2, but other acute toxicity did not differ. Late grade 2 toxicity was significantly less in the pion arm (29% at 5 years versus 48%, p = 0.002), but late grade 3 or 4 toxicity did not differ. Clinical local control was not significantly different between treatment arms (64% after 5 years with photons, 56% with pions, p = 0.6). Cause-specific and overall survival also did not differ (p = 0.7). There was a significant delay in time to first failure in the photon arm, largely as a result of decreased biochemical relapse, p = 0.01. A multivariate analysis is presented.

CONCLUSION

Pion therapy was well tolerated, with increased acute toxicity and significantly decreased late tissue injury. This contrasts with the late toxicity observed with higher LET particle therapy such as neutron therapy. No improvement in local control with pion therapy was observed.

Adjuvant radiotherapy and chemotherapy in node-positive premenopausal women with breast cancer

BACKGROUND

Radiotherapy after mastectomy to treat early breast cancer has been known since the 1940s to reduce rates of local relapse. However, the routine use of postoperative radiotherapy began to decline in the 1980s because it failed to improve overall survival. We prospectively tested the efficacy of combining radiotherapy with chemotherapy.

METHODS

From 1978 through 1986, 318 premenopausal women with node-positive breast cancer were randomly assigned, after modified radical mastectomy, to receive chemotherapy plus radiotherapy or chemotherapy alone. Radiotherapy was given to the chest wall and locoregional lymph nodes between the fourth and fifth cycles of cyclophosphamide, methotrexate, and fluorouracil.

RESULTS

After 15 years of follow-up, the women assigned to chemotherapy plus radiotherapy had a 33 percent reduction in the rate of recurrence (relative risk, 0.67; 95 percent confidence interval, 0.50 to 0.90) and a 29 percent reduction in mortality from breast cancer (relative risk, 0.71; 95 percent confidence interval, 0.51 to 0.99), as compared with the women treated with chemotherapy alone.

CONCLUSIONS

Radiotherapy combined with chemotherapy after modified radical mastectomy decreases rates of locoregional and systemic relapse and reduces mortality from breast cancer.

Prognostic significance of Bcl-2 protein expression and Bcl-2 gene rearrangement in diffuse aggressive non-Hodgkin's lymphoma

The prognostic significance of Bcl-2 protein expression and bcl-2 gene rearrangement in diffuse large cell lymphomas (DLCL) is controversial. Bcl-2 protein expression prevents apoptosis and may have an important role in clinical drug resistance. The presence of a bcl-2 gene rearrangement in de novo DLCL suggests a possible follicle center cell origin and perhaps a distinct clinical behavior more akin to low-grade non-Hodgkin's lymphoma (NHL). The purpose of this study was to determine the impact of Bcl-2 protein expression and bcl-2 gene rearrangement (mbr and mcr) on survival of a cohort of patients with DLCL who were uniformly evaluated and treated with effective chemotherapy. Patients included the original MACOP-B cohort (n = 121) and the initial 18 patients treated with the VACOP-B regimen (total = 139). All patients had advanced-stage disease, were 16 to 70 years old, and corresponded to Working Formulation categories F, G, or H. No patients had prior treatment, discordant lymphoma, or human immunodeficiency virus seropositivity. Paraffin sections from diagnostic biopsies were analyzed for bcl-2 gene rearrangement including mbr and mcr breakpoints by polymerase chain reaction and Bcl-2 protein expression by immunohistochemistry. With a median follow-up of 81 months, overall (OS), disease-free (DFS), and relapse-free survival (RFS) were measured to determine the prognostic significance of these parameters. Analyzable DNA was present in 118 of 139 (85%) cases, with 14 demonstrating a bcl-2 rearrangement (11 mbr, 3 mcr). All 14 of these bcl-2 gene rearrangement-positive cases were found in the 102 patients with a B-cell immunophenotype, but the presence of this rearrangement had no significant influence on survival. Bcl-2 protein expression was interpretable in 116 of 139 (83%) cases, with immunopositivity detected in 54 of 116 (47%). Using a cut-off of greater than 10% Bcl-2 immunopositive tumor cells for analysis, positive Bcl-2 protein expression was seen in 28 of 116 (24%) patients and the presence of this expression correlated with decreased 8-year OS (34% v 60%, P < .01), DFS (32% v 66%, P < .001), and RFS (25% v 59%, P < .001). Bcl-2 protein expression remained significant in multivariate analysis that included the clinical international prognostic index factors and immunophenotype (P < .02). In conclusion, although bcl-2 gene rearrangement status could not be shown to have an impact on outcome, Bcl-2 protein expression is a strong significant predictor of OS, DFS, and RFS in DLCLs.

Compliance with practice guidelines for node-negative breast cancer

PURPOSE

Practice guidelines for cancer management have been in use in the province of British Columbia (BC), Canada, since the mid 1970s. To evaluate practice guideline compliance, treatment received was compared with treatment recommended in a population-based cohort of women with breast cancer.

METHODS

All incident cases (n = 939) of invasive, pathologically node-negative breast cancer diagnosed in 1991 were identified from the BC Cancer Registry. Treatment details were abstracted from cancer clinic records for cases referred to the BC Cancer Agency (BCCA) (n = 661) and original source documents for nonreferred cases. Management decisions were considered compliant if the patient received the recommended treatment or was entered onto a randomized trial of the modality being assessed.

RESULTS

Overall compliance with adjuvant therapy guidelines was 97% for radiotherapy, 96% for chemotherapy, and 89% for tamoxifen. An oncology specialist was consulted by 94% of patients with an indication for adjuvant treatment and by 58% of those without an indication (odds ratio [OR] = 10.7; 95% confidence interval, 7.0 to 16.4). Compliance with a guideline to deliver radiotherapy was 95%; with chemotherapy, 77%; and with tamoxifen, 68%. Compliance with a guideline that stated no adjuvant treatment was indicated was 99% for radiotherapy, 98% for chemotherapy, and 92% for tamoxifen. Noncompliance among patients with an indication for treatment was related to nonreferral to an oncology specialist and less complete implementation of guideline changes in the community as compared with cancer center practices.

CONCLUSION

Compliance was high, but scheduled updating and more effective community implementation could further improve consistency of care.

Effects of intermittent androgen suppression on the stem cell composition and the expression of the TRPM-2 (clusterin) gene in the Shionogi carcinoma

The proportion of tumorigenic stem cells and the expression of the apoptosis-related gene, TRPM-2 (clusterin), were studied in populations of Shionogi carcinoma cells subjected to multiple cycles of androgen withdrawal and replacement (intermittent androgen suppression). The parent androgen-dependent cell line was initially transplanted into a male mouse which was castrated when the estimated weight of the resultant tumour became approximately 3 g. After the tumour had regressed to 40% or less of the original weight, it was transplanted into the next non-castrated male. This was repeated for four cycles of transplantation and castration-induced apoptosis before the tumour progressed to an androgen-independent state. The proportion of total stem cells in the tumour, as determined by in vivo limiting dilution assays in male mice, was constant during the first three cycles but increased 15-fold between the third and fourth cycles. In the parent androgen-dependent tumour before androgen ablation, the androgen-independent stem cell population formed 0.8% of the total stem cell compartment. After the fourth cycle this population increased to 47%; a population of similar size (33%, P = 0.8) was found in the androgen-independent recurrent form of the tumour induced by one-time castration. Whether androgen withdrawal therapy was intermittent or continuous, conversion to androgen independence thus occurred when one-third to one-half of the total stem cell compartment was populated by androgen-independent stem cells. The androgen-repressed TRPM-2 (clusterin) gene was actively expressed in regressing tumours after androgen ablation, and also became constitutively expressed in non-regressing tumours after the first and subsequent cycles of androgen withdrawal. Staining of cytoplasm and nuclei with anti-clusterin antibody was observed in androgen-dependent tumour cells after each cycle of intermittent androgen suppression; the nuclear staining was more intense in recurrent androgen-independent cells. The anomalous nuclear localization of clusterin, an anti-cytolytic TRPM-2 encoded protein, may serve to inhibit early events in the apoptotic process and thereby foster the generation and outgrowth of androgen-independent stem cells in an androgen-depleted environment.

Variations in breast conservation surgery for women with axillary lymph node negative breast cancer in British Columbia

A population-based study was conducted including all women diagnosed in British Columbia in 1991 with invasive node negative breast cancer (n = 942) in order to identify factors associated with variation in use of breast conserving surgery (BCS) and to determine if provincial practice guidelines were followed. Patient, disease, treatment and physician-specific information was abstracted from medical records and original source documents. 413 (44%) patients received BCS (51% and 23% in surgical candidates and non-candidates, respectively). Significant independent factors associated with BCS included patients' age, residence, family income, tumour size, tumour location, and extent of ductal carcinoma in-situ. Age and income had a significant interaction with stronger income effects in older women. A strong surgeon effect was observed which was not explained by measured surgeon attributes. Expansion of radiation treatment facilities may help address access issues. Further examination of the patient-physician relationship and of ways to assist patients in decision making is needed.

Breast cancer and hormonal contraceptives: further results. Collaborative Group on Hormonal Factors in Breast Cancer

The Collaborative Group on Hormonal Factors in Breast Cancer has brought together and reanalysed the worldwide epidemiological evidence on breast cancer risk and use of hormonal contraceptives. Original data from 54 studies, representing about 90% of the information available on the topic, were collected, checked and analysed centrally. The 54 studies were performed in 26 countries and include a total of 53,297 women with breast cancer and 100,239 women without breast cancer. The studies were varied in their design, setting and timing. Most information came from case-control studies with controls chosen from the general population; most women resided in Europe or North America and most cancers were diagnosed during the 1980s. Overall 41% of the women with breast cancer and 40% of the women without breast cancer had used oral contraceptives at some time; the median age at first use was 26 years, the median duration of use was 3 years, the median year of first use was 1968, the median time since first use was 16 years, and the median time since last use was 9 years. The main findings, summarised elsewhere, are that there is a small increase in the risk of having breast cancer diagnosed in current users of combined oral contraceptives and in women who had stopped use in the past 10 years but that there is no evidence of an increase in the risk more than 10 years after stopping use. In addition, the cancers diagnosed in women who had used oral contraceptives tended to be less advanced clinically than the cancers diagnosed in women who had not used them. Despite the large number of possibilities investigated, few factors appeared to modify the main findings either in recent or in past users. For recent users who began use before age 20 the relative risks are higher than for recent users who began at older ages. For women whose use of oral contraceptives ceased more than 10 years before there was some suggestion of a reduction in breast cancer risk in certain subgroups, with a deficit of tumors that had spread beyond the breast, especially among women who had used preparations containing the highest doses of oestrogen and progestogen. These findings are unexpected and need to be confirmed. Although these data represent most of the epidemiological evidence on the topic to date, there is still insufficient information to comment reliably about the effects of specific types of oestrogen or of progestogen. What evidence there is suggests, however, no major differences in the effects for specific types of oestrogen or of progestogen and that the pattern of risk associated with use of hormonal contraceptives containing progestogens alone may be similar to that observed for preparations containing both oestrogens and progestogens. On the basis of these results, there is little difference between women who have and have not used combined oral contraceptives in terms of the estimated cumulative number of breast cancers diagnosed during the period from starting use up to 20 years after stopping. The cancers diagnosed in women who have used oral contraceptives are, however, less advanced clinically than the cancers diagnosed in never users. Further research is needed to establish whether the associations described here are due to earlier diagnosis of breast cancer in women who have used oral contraceptives, to the biological effects of the hormonal contraceptives or to a combination of both. Little information is as yet available about the effects on breast cancer risk of oral contraceptive use that ceased more than 20 years before and as such data accumulate it will be necessary to re-examine the worldwide evidence.

Forty years of repeated screening: the significance of carcinoma in situ

Two cohorts of women born in 1914-18 and 1929-33 who participated in a cervical screening programme have been followed for over 40 years. Age-specific incidence rates of squamous carcinoma of the cervix by rank of smear and length of interval between smears are reported. The younger cohort, who had undergone more frequent screening, had lower rates of invasive disease. From these incidence rates, estimates of false-negative rates and regression rates for carcinoma in situ have been made. The false-negative rate was estimated to be about 15%. Regression seemed more frequent in younger than in older women. For the younger cohort it was estimated to be 72% and in the older 47%. A comparison of the rates of in situ carcinoma with those of invasive disease suggests that the screening of the younger cohort reduced the rate of invasive disease to at least one-half or one-third of what it would have been if screening had commenced later. Rates of disease appear less dependent on age than previously thought and are consistent with causation by an infective agent.

Compliance with the screening mammography program of British Columbia: will she return?

OBJECTIVE

To identify factors associated with compliance in the Screening Mammography Program of British Columbia (SMPBC).

METHOD

Factors associated with rescreening within 18 months (annual compliers) and between 18 to 36 months later (late compliers) were identified in a cohort of SMPBC screenees using a self-administered questionnaire.

RESULTS

Fewer than half of women initially screened within the SMPBC were annual compliers, nearly 40% not returning by 3 years. In women age 50+ years, annual compliers tended to have no prior mammography, no prior breast pain, a physician referral to SMPBC, and a normal initial SMPBC mammogram. Late compliers also tended to have no prior mammography, a physician referral, and a normal initial SMPBC mammogram.

CONCLUSIONS

Several modifiable factors associated with compliance were identified: a physician referral to the program and possibly subsequent referral back to the program after workup for an abnormal mammogram.

Cohort study of Air Canada pilots: mortality, cancer incidence, and leukemia risk

Despite the special working environment and exposures of airline pilots, data on risk of death and cancer incidence in this occupational group are limited. The authors investigated a cohort of 2,740 Air Canada pilots who contributed 62,449 person-years of observation. All male pilots employed for at least 1 year on and since January 1, 1950, were studied. The cutoff date for outcome information was December 31, 1992. Standardized mortality ratio (SMR) and standardized incidence ratio (SIR) were used to compare mortality rates and cancer incidence rates of the cohort with the respective Canadian population rates. Ninety percent confidence intervals of the SMR and SIR were calculated. Statistically significant decreased mortality was observed for all causes (SMR = 0.63, 90% confidence interval (CI) 0.56-0.70), for all cancers (SMR = 0.61, 90% CI 0.48-0.76), and for all noncancer diseases (SMR = 0.53, 90% CI 0.45-0.62). Mortality from aircraft accidents was significantly raised (SMR = 26.57, 90% CI 19.3-35.9). Significantly decreased cancer incidence was observed for all cancers (SIR = 0.71, 90% CI 0.61-0.82), rectal cancer (SIR = 0.42, 90% CI 0.14-0.96), lung cancer (SIR = 0.28, 90% CI 0.16-0.46), and bladder cancer (SIR = 0.36, 90% CI 0.12-0.82). Prostate cancer (SIR = 1.87, 90% CI 1.38-2.49) and acute myeloid leukemia (SIR = 4.72, 90% CI 2.05-9.31) were significantly increased. The preferred relative risk model for radiation-induced nonchronic lymphoid leukemia (Beir V report) was applied to the cohort by using published estimates of in-flight radiation exposures. The estimated relative risk ranged from 1.001 to 1.06 and did not differ significantly from the observed SIR (SIR = 1.88, 90% CI 0.80-3.53). However, the incidence rate of acute myeloid leukemia was significantly increased. Monitoring of in-flight radiation exposure and long-term follow-up of civil aviation crew members is needed to further assess cancer incidence and leukemia risk in this special occupational group.

Physical activity, medical history, and risk of testicular cancer (Alberta and British Columbia, Canada)

In order to evaluate risk factors for germ cell cancers, we conducted a case-control study of 510 men with testicular cancer aged 15 to 79 years and 996 randomly selected age-matched controls in the provinces of British Columbia and Alberta, Canada. Subjects completed a mailed questionnaire providing data on education level, ethnic origin, medical history, smoking, occupation, and recreational and sports activity. The response rate among cases was 80.3 percent and among controls was 68.1 percent. After controlling for age and ethnic origin, undescended testis was associated positively with risk of testicular cancer (odds ratio [OR] = 3.5; 95 percent confidence interval [CI] = 2.2-5.7) as was inguinal hernia requiring surgery (OR = 2.0, CI = 1.3-2.9), and hydrocoele (OR = 2.6, CI = 1.4-5.1). Risk of testicular cancer increased with height, with subjects taller than 180 cm having a significantly increased risk compared with those 174 cm or less (OR = 1.5, CI = 1.1-2.1). A moderate to high level of recreational activity level was associated inversely with testicular cancer risk (OR = 0.6, CI = 0.5-0.8).

Comparison of cytogenetic analysis, southern analysis, and polymerase chain reaction for the detection of t(14; 18) in follicular lymphoma

This study was undertaken to compare the ability of cytogenetic analysis (CG), Southern analysis (SA) and the polymerase chain reaction (PCR) to detect the t(14; 18) in follicular lymphoma (FL). All methodologies were performed by standard techniques. The probes used for SA included major breakpoint region (mbr) and minor cluster region (mcr) probes. The primers for PCR were identical or similar to those used by other investigators. One hundred fifteen cases of FL were ascertained by morphologic criteria, from which sufficient fresh tissue was available for both CG and molecular analysis. Eleven cases failed by both methods (nonrepresentative sampling). One hundred four cases showed evidence of an abnormal clone by CG and/or immunoglobulin gene rearrangement (IgH) studies. Cytogenetic analysis failed in 2 cases, was positive for t(14; 18) in 91 of the remaining 102 cases (89%) and detected a non-t(14; 18) close in 11 cases. An IgH clonal rearrangement was confirmed in all 104 cases. Southern analysis detected a mbr or mcr rearrangement in 78 of 104 cases (75%). Polymerase chain reaction detected an mbr or mcr rearrangement in 68 of 104 cases (65%). The use of PCR as a clinical test to detect t(14; 18)-positive lymphomas, with single primer sets for the mbr and mcr, will result in a high false-negative rate. The use of additional primers to detect uncommon breakpoints sites will be required to enhance the sensitivity of PCR for detection of t(14; 18) in malignant lymphoma.

Sunlight exposure, pigmentation factors, and risk of nonmelanocytic skin cancer. II. Squamous cell carcinoma

INTRODUCTION AND DESIGN

Squamous cell carcinoma of the skin (SCC), a common cancer in white populations, is related to sunshine exposure; however, relatively little information is available on how timing and character of exposure affect the relationship. The purpose of this study was to investigate the nature of the relationship of SCC to individual solar UV exposure after control for phenotype and pigmentary factors. All newly diagnosed cases of SCC were in men aged 25 through 79 years, ascertained in the province of Alberta from January 1, 1983, through December 31, 1984, who were approached for participation; 80% completed a standardized etiologic interview that was conducted in their homes by a trained interviewer. Control subjects were chosen at random from the Alberta Health Care Insurance Plan subscribers list, matched only by sex (male) and age (within a 5-year age group). The response rate among controls was 71%.

RESULTS

Subjects with pale skin and red hair had an elevated risk of SCC. Subjects whose mother was of southern European ancestry had a reduced risk of SCC. After accounting for pigmentary factors, no association was seen between risk of SCC and cumulative lifetime sun exposure. However, a strong trend toward increasing risk was seen with increasing chronic occupational sun exposure in the 10 years prior to diagnosis.

CONCLUSION

The results suggest that recent sun exposure (in the 10 years prior to diagnosis) may be important in accounting for individual risk of SCC.

Sunlight exposure, pigmentary factors, and risk of nonmelanocytic skin cancer. I. Basal cell carcinoma

BACKGROUND AND DESIGN

Basal cell carcinoma (BCC) of the skin is the most common neoplasm in white populations, and solar radiation is generally accepted to be the dominant environmental risk factor for this disease. However, little information is available on the nature of the relationship between BCC and sunlight. The purpose of this study was to evaluate the nature of the relationship between sunlight exposure, pigmentary factors, and BCC of the skin. A population-based case-control study of 226 male patients with BCC diagnosed from January 1, 1983, through December 31, 1984, and 406 randomly selected male control subjects was conducted in Alberta, Canada. The study was conducted using a standardized questionnaire, administered in person by trained interviewers. Data were analyzed using conditional logistic regression methods.

RESULTS

After controlling for other host and pigmentary factors, the risk of BCC was increased in subjects with light skin color and those who freckled in childhood. A history of severe sunburn in childhood also increased risk. Subjects of southern European ethnic origin were at significantly lower risk of BCC. Surprisingly, no association was seen between mean annual cumulative summer sunlight exposure and risk of BCC. A significantly increased risk of BCC was seen in subjects with increased recreational sunlight exposure in adolescence and childhood (age, 0 to 19 years), although an inverse relationship was seen with lifetime recreation exposure. The relationship with childhood sun exposure was most pronounced among sun-sensitive subjects whose skin tended to burn rather than tan in the sun.

CONCLUSIONS

The lack of association between cumulative sun exposure and BCC contradicts conventional wisdom about the cause of this tumor, and the increased risk with sun exposure at age 0 to 19 years suggests that childhood and adolescence may be critical periods for establishing adult risk for BCC.

Human pharmacokinetic study of immediate-release (codeine phosphate) and sustained-release (codeine Contin) codeine

The authors compared, in a double-blind, randomized, crossover study in 13 healthy adult volunteers, the single- and multiple-dose pharmacokinetics, relative bioavailability, and side effects of a new oral sustained-release formulation of codeine (SRC) containing 150 mg codeine base, with oral immediate-release codeine phosphate (IRC). Sustained-release codeine was given at a dose of 150 mg every 12 hours for 5 doses; IRC was given at a dose of 60 mg (2 x 30 mg) every 4 hours for the first 3 doses, and 30 mg every 4 hours thereafter for 12 doses. Plasma codeine levels were determined using a sensitive and specific high-performance liquid chromatography method and corrected for dose administered and codeine base equivalent. Mean values for single-dose pharmacokinetic parameters for SRC and IRC, respectively, were: Cmax of 217.8 and 138.8 ng/mL; Tmax of 2.3 and 1.1 hours; AUC0-inf of 1202.3 and 1262.4 ng.mL-1.hour-1; and t1/2el of 2.6 hours for both formulations. Their respective mean steady-state pharmacokinetic parameters were: Cmax of 263.8 and 222.9 ng/mL; Tmax of 3.2 and 1.1 hours; AUC0-12h of 1576.4 and 1379.1 ng.mL-1.hour-1; and t1/2el of 2.8 and 2.3 hours. These results indicate comparable bioavailability between both formulations with SRC providing delayed peak plasma levels. The sustained-release character of SRC can be explained by a delayed absorption, which is not limiting to drug elimination. Sustained-release codeine provides higher plasma codeine levels over a broader time interval and is expected to improve pain management.

Relationship between variant forms of estrogen receptor RNA and an apoptosis-related RNA, TRPM-2, with survival in patients with breast cancer

BACKGROUND

Although smaller variant forms of estrogen receptor (ER) messenger RNA (mRNA) have been detected in breast tumors, neither their prevalence nor their prognostic significance have been evaluated. Similarly, TRPM-2 mRNA, the product of a gene induced principally during the onset of apoptosis, is present in mouse and human breast cancer cell lines, but whether it also occurs in primary breast tumors and is related to disease outcome is unknown.

METHODS

The relative expression and transcript size of ER mRNA and TRPM-2 mRNA in 126 primary breast tumors were measured by Northern analysis and compared with tumor grade, hormone receptor status, extent of tumor necrosis, and survival.

RESULTS

In ER-positive tumors, 64% of the tumors had only the normal 6.5 kb ER mRNA, an additional 9% had the normal plus smaller ER mRNA, and 2% had variant forms. Only 8% of ER-negative tumors had ER mRNA transcripts. There were significant relationships between the occurrence of ER mRNA and low tumor grade, ER-positive receptor status, and better survival. In contrast, TRPM-2 mRNA was found in only 17% of breast tumors, none of which could be grouped with respect to grade, hormone receptor status, or survival.

CONCLUSIONS

The presence of smaller variant forms of ER mRNA either alone or in association with the normal ER transcript is not indicative of an unfavorable prognosis, whereas TRPM-2 mRNA occurs in many primary breast tumors, but has no apparent relationship to survival.

Chromatographic analysis and pharmacokinetics of liposome-encapsulated doxorubicin in non-small-cell lung cancer patients

A sensitive and specific quantitative assay for total doxorubicin concentrations in plasma containing liposome-encapsulated doxorubicin hydrochloride (TLC D-99) was developed, with solvent extraction and reversed-phase high-performance liquid chromatography (HPLC). Separation of doxorubicin from its metabolites was accomplished with a 15 cm x 3.9 mm i.d., microBondapak phenyl analytical HPLC column. Optimum chromatographic conditions, obtained with a mobile phase gradient from 85 to 50% (v/v) 16 mM ammonium formate buffer in tetrahydrofuran at a flow rate of 2 mL/min, gave a detection limit of 0.3 pmol/injection. Eleven-point standard curves with from 0.00595 to 29.8 microM TLC D-99 and 0.1 microM internal standard in plasma were analyzed on three separate occasions to formally validate this assay. An overall correlation coefficient of 0.9985 was found for the logarithmic transformed data. The pharmacokinetic characteristics of doxorubicin were investigated after administration of TLC D-99 to 12 non-small-cell lung cancer patients as an intravenous infusion at doses of 60 and 75 mg/m2. The data are best described by a three-compartment model with alpha, beta, and gamma elimination half-lives of 0.0721, 2.84, and 25.2 h for the 60-mg/m2 group and 0.103, 2.56, and 14.9 h for the 75-mg/m2 patients. A mean plasma clearance of 9.89 L/h (range: 1.95 to 23.4 L/h) was found for the 60-mg/m2 patients, with that from the 75-mg/m2 group being within these values. Mean area under the plasma concentration versus time curve estimates of 37.1 and 47.9 microM/h were observed for the patients receiving 60 and 75 mg/m2, respectively. The plasma concentration-time course for total doxorubicin following administration of TLC D-99 suggests that the disposition of the liposomal formulation is determined more by the pharmacokinetics of the liposome than the encapsulated drug.

Calculating the prevalence of cancer

Incidence, prevalence and mortality are commonly used measures to assess the impact of disease on human populations. Prevalence, although regularly assessed for a number of different diseases, has only had recent use to measure the impact of cancer. The calculation of the prevalence of cancer presents several difficulties since there is no reporting mechanism established to measure the proportion of the community that has the disease. In the absence of such a mechanism, mortality data linked to incidence data from cancer registries have been used. The assumption is made that once diagnosed with cancer an individual remains a prevalent case until death. In this paper we present alternatives to this assumption and use them to produce estimates of cancer prevalence. We illustrate the effect of these assumptions on the calculated prevalence of cancer using data from the British Columbia Cancer Registry.

Cigarette and alcohol use in patients with adenocarcinoma of the gastric cardia or lower esophagus

The authors studied the cigarette and alcohol use of 243 patients with adenocarcinoma of the cardia or lower esophagus, including 66 with Barrett's metaplasia (esophagocardia group). They compared results of that investigation with the cigarette and alcohol use of 303 patients with squamous carcinoma of the esophagus, a cancer in which an etiologic association is proven, and of 338 patients with stomach cancer not involving the cardia, a cancer in which there is little or no association with cigarettes or alcohol. Controlled for other variables, patients with squamous cancer used more cigarettes and alcohol than the other two groups. There was no significant difference in cigarette or alcohol use between patients with esophagocardia and stomach cancer or between those in the esophagocardia group with or without Barrett's metaplasia. Because cigarette and alcohol use was not greater in patients with esophagocardia than in those with stomach cancer, the authors do not think that such factors explain the increasing incidence of adenocarcinoma of the cardia or lower esophagus.

Human papillomavirus infection of the uterine cervix. Tissue sampling and laboratory methods affect correlations between infection rates and dysplasia

Two common tissue sampling techniques--colposcopic biopsy and cervical scrape--and two common human papillomavirus (HPV) detection techniques--Southern blot and dot blot (SB and ViraPap [VP])--were compared to determine whether differences in these techniques alter correlations between "oncogenic" HPVs and cervical neoplasia. In 87 women with persistently abnormal Papanicolaou (Pap) smears, concurrent biopsy and scrape specimens contained HPV in 21 (24%) and contained no HPV in 26 (30%); 30 scrape specimens (34.5%) tested positive when the biopsy tested negative and 10 (11.5%) scrape specimens tested negative when the biopsy tested positive (overall concordance, 54%). Concordance for the most prevalent HPVs (16/18) was 59%. In carcinoma in situ, HPV was found in biopsy samples significantly more frequently than in scrape specimens: 17 of 23 (75%) biopsy samples versus 9 of 23 (39%) scrape specimens (P = 0.018). Conversely, in mild or no dysplasia, 0 of 42 biopsy samples tested positive for HPV 16/18 compared with 12 of 42 scrape specimens (29%; P = 0.0001). Of 229 specimens analyzed by SB and VP, 43 (19%) tested positive and 148 (65%) tested negative for HPV by both methods (concordance, 84%). Corroborative results indicated that 29 of 35 (83%) VP-positive SB-negative results were truly positive compared with none of three SB-positive VP-negative results. Both the cervical sampling technique and the method for HPV detection can significantly affect statistical correlations between cervical dysplasia and HPV type.

Yeast in blood cultures. Evaluation of factors influencing outcome

Sixty episodes of candidemia occurring between January 1987 and September 1989 were retrospectively reviewed and the outcome was compared for three patient categories: neutropenic, postsurgical, and nonneutropenic nonsurgical. Because of increasing reports of resistant yeasts, minimal inhibitory concentrations (MICs) to amphotericin B (amB) were determined to examine its relationship to patient outcome. No significant differences between patient categories were found for selected risk factors, mortality, or species isolated, although there was a tendency for Candida tropicalis to occur in neutropenic patients. Statistical analysis using logistic regression showed that both an amB dose greater than 500 mg and a yeast MIC greater than 0.78 micrograms/ml were independent prognosticators of patient outcome.

Reliability of dietary information from surrogate respondents

A self-administered food frequency questionnaire was included as part of a case-control study of breast cancer in 1980-82. In 1986-87, a second food frequency questionnaire was sent to surviving cases and husbands of deceased cases; 30 spouses (86% response rate) and 263 surviving cases (88% response rate) returned questionnaires. The dietary questions concerned consumption of specific food items by the case before diagnosis of breast cancer. Missing values were less common in the second questionnaire; there was no significant difference in missing values between surviving cases and spouses of deceased cases. Kappa statistics comparing responses in the first and second questionnaires were significantly lower for spouses of deceased cases than for surviving cases. Reported level of confidence by the husbands regarding knowledge about their wives' eating habits did not influence the kappa statistics or the frequencies of missing values. The lack of good agreement has important implications for the use of proxy interviews from husbands in retrospective dietary studies.

Identifying effective treatments for uremic pruritus

The identification of effective treatments for uremic pruritus used a literature search of MEDLINE (1966 to March 1991), Index Medicus (1978 to March 1991), bibliographic reviews of textbooks, and pertinent articles. Only randomized controlled clinical trials were selected for analysis. Assessment of study quality was performed independently by two observers with specific methodologic criteria. A clinically significant therapeutic effect was defined as a statistically significant result in the proportion of patients improving and a reduction in pruritus score of at least 50%. Clinically significant outcomes were obtained for two of three whole-body ultraviolet B trials. Meta-analysis of the ultraviolet B trials retained the significant effect in analysis of proportions (pooled odds ratio 18; 95% confidence interval 4, 161). Trials of lidocaine, charcoal, and nicergoline demonstrated either statistically significant improvement in pruritus score or in proportions, but not both. Ultraviolet B phototherapy is the treatment of choice in moderate to severe uremic pruritus.

Effectiveness of transcutaneous electrical nerve stimulation (TENS) for analgesia during biliary lithotripsy

The effectiveness of transcutaneous electrical nerve stimulation (TENS) in controlling pain during biliary extracorporeal shockwave lithotripsy (BESWL) was assessed in 100 patients with symptomatic gallbladder calculi. Patients were divided into four groups: TENS electrodes were placed on the back at cutaneous anesthesia sites and on the right leg and the gallbladder acupuncture site in groups A and B. Electrodes were "turned on" only in group A. In groups C and D, electrodes were placed only on the back at cutaneous dermatomes. Electrodes were "turned on" in group C only. The TENS unit was stimulated at the pulse rate of 60 to 100 microseconds and frequency of 80 to 125 Hz. Lithotripsy was performed with the Lithostar Plus overhead module. The differences in the amount of analgesic used and the pain experiences by the patients in all groups were not statistically significant. The proportion of patients requiring intravenous analgesia in each group was also not significantly different (72%, 80%, 68%, 76% in groups A to D, respectively). Thus, TENS did not help in reducing the amount of intravenous analgesia required or the average pain perceived by the patient during lithotripsy treatment.

Melanocytic nevus density in Asian, Indo-Pakistani, and white children: the Vancouver Mole Study

Melanocytic nevus density in 378 Asian and 68 Indo-Pakistani school children 6 to 18 years of age was compared with that in 1146 white children of the same age range. At all ages, the number of melanocytic nevi 2 mm or larger per square meter of body surface area was substantially lower in Asians and Indo-Pakistanis than in white persons. Among white persons characteristics associated with a higher risk of cutaneous melanoma in adults, that is, light skin color, a propensity to burn rather than tan in the sun, and a history of numerous or severe sunburns, are also associated with the highest melanocytic nevus density in children. Examination of these same host pigmentation and sunburn factors among Asian children revealed no association with nevus density.

Relative operating characteristic analysis and group modeling for tumor markers: comparison of CA 15.3, carcinoembryonic antigen, and mucin-like carcinoma-associated antigen in breast carcinoma

Relative operating characteristic (ROC) analysis was used to examine the clinical applicability of 3 breast carcinoma tumor markers, CA 15.3, carcinoembryonic antigen, and mucin-like carcinoma-associated antigen. Each tumor marker was quantitated in single serum samples collected from 100 normal blood donors, 60 patients with nonmalignant diseases, 33 women at high risk for breast carcinoma, 30 patients with malignancies other than breast carcinoma, and 158 breast carcinoma patients including 67 with no evidence of disease following surgery, 46 with a tumor burden less than 5 g, and 45 with a tumor burden greater than 5 g. These were used to construct models for early diagnosis among those at high risk for breast carcinoma, the influence of nonmalignant disease on early diagnosis, discrimination of breast carcinoma from other adenocarcinomas, detection of early recurrence, and assessment of change in tumor burden. For each model ROC data permitted the unbiased selection of the most appropriate critical values based on the interaction of sensitivity and specificity. ROC analysis indicated that in practice the assays were remarkably similar. While CA 15.3 generally performed best, there was significant variation among models. Optimal marker selection can thus depend on specific clinical application. In some cases ROC identified a combination of markers as superior to any single assay, but this was not statistically significant.

Dose-intensity meta-analysis of chemotherapy regimens in small-cell carcinoma of the lung

To determine if chemotherapy dose intensity (DI) influences treatment outcome, 60 published studies in limited- and extensive-stage small-cell carcinoma of the lung (SCCL) were retrospectively analyzed for relationship between intended DI and response (complete response [CR] or partial response [PR]) or median survival (MS). Agents used in the regimens included cyclophosphamide (C), doxorubicin (A), vincristine (V), etoposide (E), and cisplatin (P). Relative DI (RDI) of each study regimen was calculated against a reference regimen, and weighted regression analysis was used. Additionally, analysis of individual drug RDI within combinations was performed. For CAV, increasing RDI of the regimen showed no correlation with outcome. For the individual drugs, C RDI correlated positively, while A RDI correlated negatively with attainment of CR in limited disease, but both only after unduly influential observations were eliminated. In extensive-stage disease, A RDI correlated positively with CR+, PR but only in randomized trials, and this correlation lost statistical significance after unduly influential observations were eliminated. For CAE and CAVE, the RDI of the regimens correlated positively with MS in extensive-stage disease as did the C RDI. In limited disease, the C RDI correlated negatively with MS. For EP, no significant correlations were seen. We conclude that DI-outcome correlations are not consistent for these chemotherapy regimens in SCCL. Meta-analysis of retrospective data can generate hypotheses for testing in prospective clinical trials, but study sample and method of analysis can appreciably affect conclusions.

Loss of androgen dependence is associated with an increase in tumorigenic stem cells and resistance to cell-death genes

Complete remissions of the androgen-dependent Shionogi mouse mammary carcinoma are observed after androgen withdrawal but invariably the disease recurs and is refractory to further hormonal manipulations. To determine the proportions of androgen-dependent (AD) and -independent (AI) tumorigenic stem cells in parent and recurrent tumors an in vivo limiting dilution assay was developed. There was a marked enrichment of stem cells in the recurrent tumors (1/200 tumor cells) relative to the parent tumors (1/4000 tumor cells) when assayed in male hosts. By assaying tumor takes in female mice, the proportion of AI stem cells was found to be 1/370,000 tumor cells in the parent vs 1/800 tumor cells in the recurrent carcinoma; a 500-fold increase in AI stem cells resulting from androgen-withdrawal. Unexpectedly, no enrichment of AI stem cells was evident in regressing parent tumors; rather, the proportion of such cells was very small (1/2,200,000 tumor cells). This finding implies that the AI cells which survive androgen withdrawal may result from the ability of small number of initially AD stem cells to adapt to an altered hormonal environment. This adaptive process was further defined in terms of the disappearance of androgen receptors from the nucleus and the expression of androgen-repressed genes including the proto-oncogenes, c-fos and c-myc, and the cell death gene, TRPM-2; all of which are constitutively active in recurrent AI tumor cells. Overall, our results indicate: (1) the tumor mass consists mainly of differentiated cells; (2) stem cells initially are AD but at most the killing effect of androgen-withdrawal will be limited to 2-3 logarithms before compensatory adaptive mechanisms supervene; and (3) progression of stem cells to an AI state, in which they are resistant to the killing effects of cell death genes, might be prevented by the inhibition of androgen-repressed adaptive mechanisms which come into play when androgens are withdrawn.

Suntan, sunburn, and pigmentation factors and the frequency of acquired melanocytic nevi in children. Similarities to melanoma: the Vancouver Mole Study

The association between prevalence of benign melanocytic nevi and a number of skin cancer risk factors was examined among 913 white Vancouver (Canada) school children aged 6 to 18 years. Subjects with light skin, with a propensity to burn rather than tan in the sun, and with numerous or severe sunburns in the previous 5 years had significantly higher nevus counts than individuals without these characteristics. Subjects who acquired deeper tans tended to have fewer nevi than those who did not tan. Finally, children who freckled had higher nevus counts than those who did not freckle. These findings in children are similar to those seen in studies of malignant melanoma among adults and suggest that strategies to reduce melanoma incidence should begin with young children.

Effects of androgen withdrawal on the stem cell composition of the Shionogi carcinoma

The parent Shionogi mouse mammary carcinoma is androgen dependent but cells that survive hormone withdrawal progress and give rise to an androgen-independent tumor. To determine whether renewed growth might be attributed to the persistence or partial recovery of an androgenic stimulus, we compared the amount of dihydrotestosterone and nuclear androgen receptor in parent and recurrent tumors. The whole tissue concentration of dihydrotestosterone in the parent tumor before castration was 1.40 +/- 0.46 (SE) as compared with 0.22 +/- 0.10 pmol/mg of DNA in the recurrent tumor. The initial concentration of nuclear androgen receptor in the parent was 0.65 +/- 0.12 pmol/mg of DNA; this was reduced to zero within 24 h after castration. Also in keeping with the androgen independence, no receptor was detected in the nuclear fraction of the recurrent carcinoma. In an attempt to relate malignant potential to nonhormonal factors associated with progression, we compared the proportions of androgen-dependent and -independent tumorigenic (stem) cells in parent and recurrent tumors using an in vivo limiting dilution assay. The difference observed, i.e., one stem cell per 4000 tumor cells in the parent versus one stem cell per 200 tumor cells in the recurrent carcinoma, was consistent with a marked enrichment of stem cells in the latter. The proportion of androgen-independent stem cells was also determined by assaying tumor takes in female hosts. The difference, i.e., one stem cell per 370,000 tumor cells in the parent versus one stem cell per 800 tumor cells in the recurrent carcinoma, demonstrated a striking 500-fold increase in androgen-independent stem cells resulting from androgen withdrawal. Unexpectedly, no enrichment of androgen-independent stem cells was evident in regressing parent tumors; rather, the proportion of such cells was very small, i.e., one androgen-independent stem cell per 2,200,000 regressing parent cells. This finding implies that the androgen-independent state of cells which survive androgen withdrawal may result from the ability of a small number of initially androgen-dependent stem cells to adapt to an altered hormone environment.

Anatomic distribution of acquired melanocytic nevi in white children. A comparison with melanoma: the Vancouver Mole Study

The presence of acquired benign nevi is a risk factor for cutaneous melanoma, yet relatively little is known about the etiology of nevi. We have conducted a study of the prevalence of melanocytic nevi among 1146 white Vancouver (Canada) schoolchildren aged 6 to 18 years. Numbers of nevi per square meter of body surface area increase with age in children of both sexes. Male adolescents have more nevi than female adolescents on the head and neck as well as on the trunk, while prevalence in females is higher on the upper and lower limbs. This distribution parallels that of cutaneous melanoma in British Columbia adults. Nevi are more common in children on intermittently exposed body sites than on constantly or minimally sun-exposed sites. This suggests that exposure to strong intermittent sunlight in childhood (a risk factor for cutaneous melanoma) may also be important in the etiology of acquired benign nevi.

Diet and histologic types of benign breast disease defined by subsequent risk of breast cancer

The authors investigated the relation between diet and histologic types of benign breast disease defined by subsequent risk of breast cancer in a case-control study of volunteers who entered the Vancouver Center of the Canadian National Breast Screening Study between 1983 and 1985. Proliferative benign breast disease (n = 124) was inversely associated with vitamin A supplementation (vitamin A user vs. nonuser, odds ratio (OR) = 0.5) and frequent green vegetable consumption (frequent vs. rare consumption, OR = 0.3), whereas severe atypias and borderline carcinoma in situ (n = 32) were directly associated with frequent meat fats consumption (frequent vs. rare consumption, OR = 3.2) with no association with vitamin A or vegetable consumption. No dietary relations were found for histologic types of benign breast disease at no increased risk for subsequent breast cancer (n = 274). The implications of these findings in relation to the etiology of breast cancer are discussed.