Long-Term Follow-Up Analysis of NRG Oncology RTOG 0415: A Randomized Phase III Non-Inferiority Study Comparing Two Fractionation Schedules in Patients with Favorable-Risk Prostate Cancer

PURPOSE/OBJECTIVE(S)

To assess whether the efficacy of a hypofractionated (H) schedule is no worse than a conventional (C) schedule in men with low-risk prostate cancer.

MATERIALS/METHODS

Accrual began April 2006 and ended in December 2009. 1115 men with favorable-risk prostate cancer were randomly assigned 1:1 to a conventional (C) schedule (73.8 Gy in 41 fractions over 8.2 weeks) or to a hypofractionated (H) schedule (70 Gy in 28 fractions over 5.6 weeks). The trial was designed to establish with 90% power and alpha = 0.05 that (H) results in 5-year disease-free survival (DFS) that is not lower than (C) by more than 7% (hazard ratio (HR) < 1.52). Protocol specified secondary endpoints evaluated for noninferiority include: biochemical recurrence (BR), local progression, disease-specific survival, and overall survival.

RESULTS

One thousand ninety-two protocol eligible men were analyzed: 542 to C and 550 to H. Median follow-up is 12.75 years. Baseline characteristics were not different according to treatment arm. The estimated 12-year DFS is 56.1% (95% CI 51.5, 60.5) in the C arm and 61.8% (57.2, 66.0) in the H arm. The DFS hazard ratio (H/C) is 0.85 (0.71-1.03), confirming non-inferiority (p<0.001). Twelve-year cumulative incidence of biochemical recurrence (BR) was 17.0% (CI 13.8, 20.5) in the C-RT and 9.9% (CI 7.5, 12.6) in the H-RT arm; (HR = 0.56, (0.40-0.78) suggesting improved efficacy with H. Additional pre-specified secondary endpoints were non-inferior Late Grade ≥ 3 GI toxicity is 3.2% (C) vs. 4.4% (H), Relative risk (RR) for H vs. C 1.39 (CI 0.75, 2.55) Late Grade ≥ 3 GU toxicity is 3.4% (C) vs. 4.2% (H), RR = 1.26 (CI 0.69, 2.30).

CONCLUSION

In men with favorable-risk prostate cancer, long-term disease-free survival is non-inferior with 70 Gy in 28 fractions compared to 73.8 Gy in 41 fractions. The risk of BR is reduced with moderate hypofractionation. No differences in late Grade ≥3 GI/GU toxicity were observed between the arms. (ClinicalTrials.gov identifier: NCT00331773).

Progression-Free Survival as a Surrogate Endpoint of Overall Survival in Patients with Locally Advanced Non-Small Cell Lung Cancer Treated with Chemoradiotherapy: Trial-Level Meta-Analysis and Individual-Level Analysis of NRG/RTOG 0617 and PROCLAIM

PURPOSE/OBJECTIVE(S)

Overall Survival (OS) is the gold standard endpoint in randomized clinical trials (RCTs) of Locally Advanced Non-Small Cell Lung Cancer (LA-NSCLC). Intermediate endpoints that can be observed at earlier time points and predict OS would improve trial efficiency and expedite the adoption of proven interventions.

MATERIALS/METHODS

Atrial-level meta-analysis was conducted using a weighted regression analysis to quantify the correlation between PFS and OS hazard ratios (HRs). Large (n≥ 100) contemporary RCTs in LA-NSCLC that used platinum-based chemoradiation were included. An individual-level surrogacy analysis based on Prentice criteria was performed to evaluate if PFS could reliably predict OS using NRG/RTOG 0617 (NCT00533949), a phase III RCT of dose escalated CRT. The individual-level correlation between PFS and OS was validated using PROCLAIM (NCT00686959) control arm.

RESULTS

Nineteen RCTs comprising a total of 5525 patients (pts) were included in the trial-level meta-analysis. A moderately high correlation was observed between PFS HR and OS HR (R2 = 0.68, 95% CI = 0.42-0.94). Individual-level analysis of NRG/RTOG 0617 showed that, as reported, RT dose was associated with OS (HR = 1.28, 95% CI = 1.04-1.58, p = 0.02) and PFS (HR = 1.21, 95% CI = 0.99-1.46, p = 0.06). Progressive disease (PD) was highly associated with OS, where pts having PD within 6mo or 12mo had a significantly higher mortality risk than those not having PD within 6mo or 12 mo, respectively, in landmark analysis (PD within 6mo: HR = 2.56, 95% CI = 1.82-3.59, p<0.0001; PD within 12mo: HR = 3.18, 95% CI = 2.45-4.12, p<0.0001). Accounting for PD moderately reduced RT dose effect on OS (HR = 1.21, 95% CI = 0.98-1.49), suggesting RT dose effect on OS may be mediated partially through PD. The association between OS and PD occurrence within 6mo or 12mo was similar in PROCLAIM control arm (PD within 6mo: HR = 2.06, 95% CI = 1.48-2.86, p<0.0001; PD within 12mo: HR = 2.02, 95% CI = 1.38-2.95, p<0.0001).

CONCLUSION

A moderately high trial-level surrogacy between PFS and OS was identified in trial-level meta-analysis. PD occurrence also reliably predicted OS at the individual patient level in both NRG/RTOG 0617 and PROCLAIM. These results support the use of PFS as a valid endpoint in clinical trials of LA-NSCLC.

Disease volumes as a marker for patient response in malignant pleural mesothelioma

BACKGROUND

The goal of this study was to create a comprehensive model for malignant pleural mesothelioma patient survival utilizing continuous, time-varying estimates of disease volume from computed tomography (CT) imaging in conjunction with clinical covariates.

PATIENTS AND METHODS

Serial CT scans were obtained during the course of clinically standard chemotherapy for 81 patients. The pleural disease volume was segmented for each of the 281 CT scans, and relative changes in disease volume from the baseline scan were tracked over the course of serial follow-up imaging. A prognostic model was built using time-varying disease volume measurements in conjunction with clinical covariates.

RESULTS

Over the course of treatment, disease volume decreased by an average of 19%, and median patient survival was 12.6 months from baseline. In a multivariate survival model, changes in disease volume were significantly associated with patient survival along with disease histology, Eastern Cooperative Oncology Group performance status, and presence of dyspnea.

CONCLUSIONS

Analysis of the trajectories of disease volumes during chemotherapy for patients with mesothelioma indicates that increasing disease volume was significantly and independently associated with poor patient prognosis in both univariate and multivariate survival models.

Patterns of missing mini mental status exam (MMSE) in radiation therapy oncology group (RTOG) brain cancer trials

The Mini Mental Status Exam (MMSE) instrument has been commonly used in the Radiation Therapy Oncology Group (RTOG) to assess mental status in brain cancer patients. Evaluating patient factors in relation to patterns of incomplete MMSE assessments can provide insight into predictors of missingness and optimal MMSE collection schedules in brain cancer clinical trials. This study examined eight RTOG brain cancer trials with ten treatment arms and 1,957 eligible patients. Patient data compliance patterns were categorized as: (1) evaluated at all time points (Complete), (2) not evaluated from a given time point or any subsequent time points but evaluated at all the previous time points (Monotone drop-out), (3) not evaluated at any time point (All missing), and (4) all other patterns (Mixed). Patient characteristics and reasons for missingness were summarized and compared among the missing pattern groups. Baseline MMSE scores and change scores after radiation therapy (RT) were compared between these groups, adjusting for differences in other characteristics. There were significant differences in frequency of missing patterns by age, treatment type, education, and Zubrod performance status (ZPS; P < 0.001). Ninety-two percent of patients were evaluated at least once: seven percent of patients were complete pattern, 49% were Monotone pattern, and 36% were mixed pattern. Patients who received RT only regimens were evaluated at a higher rate than patients who received RT + other treatments (49-64% vs. 27-45%). Institutional error and request to not be contacted were the most frequent known reasons for missing data, but most often, reasons for missing MMSE was unspecified. Differences in baseline mean MMSE scores by missing pattern (Complete, Monotone dropout, Mixed) were statistically significant (P < 0.001) but differences were small (<1.5 points) and significance did not persist after adjustment for age, ZPS, and other factors related to missingness. Post-RT change scores did not differ significantly by missing pattern. While baseline and change scores did not differ widely by missing pattern for available measurements, incomplete data was common and of unknown reason, and has potential to substantially bias conclusions. Higher compliance rates may be achievable by addressing institutional compliance with assessment schedules and patient refusal issues, and further exploration of how educational and health status barriers influence compliance with MMSE and other tools used in modern neurocognitive batteries.

Understanding differences in the receipt of chemotherapy between African-American (AA) and white (W) patients with stage III colon cancer

6568

Background: Even when stage is controlled for, AA are more likely to die from colon cancer than are W. Previous research suggests that AA are less likely to receive adjuvant chemotherapy for Stage III colon cancer than W. This study examines the differences in the receipt of chemotherapy for stage III colon cancer and the reasons behind those differences. Methods: The records of patients diagnosed with and/or receiving their first-course of treatment for Stage III colon cancer at the University of Chicago between 1995–2004 were examined. Specifically, patient charts were audited to determine whether the patients had received chemotherapy, and if not, the documented reasons for the non-receipt of therapy. In the case of incomplete records, the patients’ outside physicians were contacted to ascertain the chemotherapy history. Chemotherapy information was unavailable for only 13 patients (5 AA and 8 W). Results: A total of 186 patients (110 AA and 76 W) were diagnosed with stage III colon cancer at the University of Chicago between 1995–2004. No significant differences were seen with respect to age, sex or tumor location between AA and W. In total, 65% of AA versus 82% of W received chemotherapy (OR 0.43; 95% CI: 0.20–0.86). AA were more likely to not undergo chemotherapy because of comorbidities (OR 3.80; 95%CI 1.35–10.50). Those pts not receiving therapy because of comorbidities had a poorer overall survival than those who received therapy (HR 5.9; 95%CI 3.4–10.3). This effect held for both AA and W pts (p=0.65 for race and comorbidity interaction). Among the 146 pts (86AA, 63W) for whom it is known that chemotherapy was recommended, AA were over 9 times as likely to have a documented refusal (OR 9.5; 95% CI 1.19–75.4). These findings were robust to adjustments for age, sex, insurance status and marital status. Conclusions: AA were significantly less likely than W to receive chemotherapy for stage III colon cancer. The reasons for the difference include both refusal of therapy and the presence of comorbidities that the treating physicians felt were a contraindication to therapy. Future research should be directed at better understanding the reasons behind the higher refusal rates for AA patients.

No significant financial relationships to disclose.

Health-related quality of life among high-risk women in an MRI surveillance study

1522

Background: The quality of life (QOL) and psychological impact of incorporating MRI into breast cancer screening programs for high-risk women (HRW) has not been well studied. Psychological and biological risk factors, e.g. cancer history, BRCA mutation, imaging recall, generalized anxiety or clinical depression may mediate QOL outcomes. Methods: 100 HRW undergoing intensive surveillance including yearly mammography, semiannual breast ultrasound and breast MRI have completed QOL (SF-36), anxiety (STAI) and depression (Beck) questionnaires at semi-annual visits. 56 HRW have completed 3 screenings. Differences in QOL measures over time were evaluated using longitudinal regression models. Differences between participants and population norms (PN), women with/without a history of cancer and with/without a BRCA mutation were assessed using t-tests. Results: QOL scores increased over time and were statistically significant for the general health (GH) subscale (p=0.016). All QOL subscales were higher than PN at baseline and were significantly higher than PN at 12 months. Mean GH score at 12 months = 80.0, PN 72.7 (SD14.2, p<0.01). Mean mental health score at 12 months = 78.9, PN 73.4 (SD14.9, p<0.01). At baseline, BRCA carriers had lower QOL scores than non-carriers and women with a history of cancer had higher QOL scores than unaffected participants, although these differences were not statistically significant. Conclusions: These data suggest that intensive breast cancer screening incorporating breast MRI may have a positive effect among HRW. Continued enrollment will allow for multi-variate characterization of psychological and biological predictors of change in QOL and psychological well-being among high-risk women undergoing intensive screening.

No significant financial relationships to disclose.

Content and method of parental disclosure of genetic risk to young adult and minor children in BRCA families

1536

Background: Prior research has found that many BRCA mutation carriers report discussing their genetic test results with their minor children. The content, method and process of this communication have not been previously described. Methods: 20 parents (yielding 42 parent-offspring pairs, POP) have completed a 62-item questionnaire regarding the content and methods of communication of genetic risk to offspring. Results: Of 19 (45%) POP where parents reported disclosure of their BRCA mutation to offspring in response to a binary (yes/no) question, all reported telling their children about the genetic mutation itself, as well as the parents’ risk for cancer. In 74% of POP the offspring’s chance of inheriting the mutation or risk for cancer were said to have been communicated. In 53% of POP parents reported discussion of parental risk reduction measures, and in only 37% of POP parents reported communication of offspring risk reduction measures. Of the POP where parents reported some communication of cancer risk, 22% described incorporating written materials. In 75% of POP parents reported communication through multiple conversations over time (1 -20 conversations, up to 4 years). Conclusions: Although many BRCA carriers report discussing their genetic mutation with offspring, the content and extent of parental communication is variable, often including information regarding the genetic mutation, but less frequently the offspring’s risk of inheriting the gene and infrequently communication regarding risk reduction measures. Further research on this expanding cohort will allow for analyses of parent and child factors associated with disclosure content in order to guide the development of interventions to facilitate age and content-appropriate communication of genetic risk to at-risk offspring.

No significant financial relationships to disclose.

Time-dependent patterns of recurrence after early stage breast cancer: Preliminary observations and methodological issues

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Background: For patients with lymph node-negative (n0) breast cancer, benefit from adjuvant therapy is established. However, absolute gains are smaller than in node-positive disease and thus more selective use is warranted, prompting development of risk profiling to identify those most (or least) likely to benefit. In addition to defining risk based on recurrence-free status to specific time landmarks, examination of the magnitude and changes in the risk (hazard) of failure over time may be informative. We investigate recurrence hazards in n0 breast cancer. Methods: In a cohort of 9,279 participants from 5 NSABP randomized trials (accrual 1982–1998) investigating cytotoxic chemotherapy (CTX) and tamoxifen (TAM) for n0 breast cancer, we examine recurrence-free survival curves and recurrence hazards over time. The latter presents analytic challenges, because empirical (i.e., nonparametric) estimates are too unstable to provide reliable inference on patterns and do not incorporate covariates, while traditional semi-parametric (i.e., Cox) and parametric survival models are too restrictive to permit hazard changes. We apply flexible extensions of these models to examine and compare time-varying hazard profiles. Results: In patients undergoing surgery only, distinctive recurrence risk patterns between estrogen receptor (ER)-negative (-) and ER- positive (+) patients emerge. We observe an earlier, larger hazard peak in ER- patients, but a more persistent hazard in ER+ patients and a crossover (hazard for ER+ > ER-) occurring around 48 months. Under adjuvant treatment (CTX in ER- and TAM or TAM+CTX in ER+), magnitudes of failure hazards are reduced but other inter-relationships are largely maintained. For example, while TAM decreases the early hazard in ER+ patients to a level comparable to CTX treated ER- disease, in later follow-up (>5 years) the ER+ hazard again exceeds that of ER- patients. Adding CTX to TAM results in hazard reductions in both early and later periods. Conclusions: Examination of recurrence hazards over time with our models reveals changes in risk that may have biologic and therapeutic strategy relevance. The proposed analytic approaches address shortcomings of standard methods and will be developed further.

No significant financial relationships to disclose.

Conditional survival for patients with colon cancer: An analysis of National Surgical Adjuvant Breast and Bowel Project (NSABP) trials C-03 through C-06

6005

Background: Survival for cancer patients is usually only reported as survival from time of diagnosis to some time landmark (e.g., 5 yrs). For pts surviving one or more years after diagnosis, however, their survival probability changes, and is more accurately depicted by conditional survival (CS), defined as the probability of surviving for an additional fixed time interval given that the pt has already survived a period of time. The purpose of this study was to determine the 5-yr CS of colon cancer pts in 4 NSABP trials. Methods: We analyzed long-term overall survival data from the 5587 colon cancer pts who were enrolled in fluorouracil (or equivalent) arms of NSABP trials C-03 through C-06. We computed observed 5-yr overall CS for pts who had already survived without disease from 0 to 5 yrs after diagnosis, and stratified the results by age, sex, race, stage, number of positive nodes, number of nodes resected, tumor location, and performance status. Results: The Table below shows the 5-yr overall CS for all pts and for selected subgroups for different survival times since diagnosis. As disease-free survival time since diagnosis increased, 5-yr observed overall CS increased from 76% to 90% at 5 yrs. For pts under age 50, CS increased from 78% to 95% at 5 yrs, but for pts > 70 yrs, CS remained fairly constant (71–82%). For pts with > 10 positive nodes, CS increased from 37% to 81% at 5 yrs, but did not change appreciably for node-negative pts (87–92%). Dukes’ C pts saw an increase in CS from 68% to 88% at 5 yrs, while CS for Dukes’ B pts did not change appreciably. Conclusion: Projected survival probability generally increases with time for colon cancer pts who remain disease-free for a period of time after diagnosis, and conditional survival can provide more informative prognostic information for these pts. An additional effect is that prognostic factors that are important at baseline become less important for conditional survival as the disease-free period increases.

[Table: see text]

No significant financial relationships to disclose.

Efficacy of systemic adjuvant therapy for breast cancer in African-American and Caucasian women

Observed variations in breast cancer survival by racial/ethnic background have been attributed to many factors, including differences in clinical and pathologic disease features at diagnosis and economic resource inequities that may affect treatment access and quality. In this report, we examine outcomes for African-American and Caucasian breast cancer patients participating in selected randomized clinical trials of the National Surgical Adjuvant Breast and Bowel Project (NSABP) to determine whether prognosis or efficacy of systemic adjuvant therapy differed between these groups. Randomized clinical trials offer the advantages of a similar disease stage and a uniform treatment plan for all participants. Patients from four NSABP trials enrolling patients from 1982 through 1994 with axillary lymph node-negative disease (543 African-American and 7582 Caucasian) and three trials enrolling patients from 1984 through 1991 with axillary lymph node-positive disease (548 African-American and 4986 Caucasian) were included. Disease-free survival (DFS), which was defined as time on study free of breast cancer recurrence, second primary cancer, or death preceding these events, and survival risk ratios (RRs) with two-sided 95% confidence intervals (CIs) for African-Americans versus Caucasians were computed from Cox proportional hazards models that included relevant prognostic covariates. Treatment benefits for the therapies evaluated in these trials were estimated separately for African-Americans and for Caucasians. Among patients with lymph node-negative disease, African-Americans had similar DFS rates to Caucasians (African-American/Caucasian RR = 1.06, 95% CI = 0.92 to 1.23) but had modestly greater mortality rates (RR = 1.21, 95% CI = 1.01 to 1.46). Among lymph node-positive patients, DFS was similar (RR = 1.04, 95% CI = 0.93 to 1.17) and survival was again less favorable for African-Americans (RR = 1.18 95% CI = 1.03 to 1.34). Survival excluding deaths most likely attributable to causes other than cancer was similar between African-Americans and Caucasians (RR = 1.08 [95% CI = 0.88 to 1.33] for lymph node-negative patients and RR = 1.09 [95% CI = 0.96 to 1.25] for lymph node-positive patients). Among lymph node-negative and lymph node-positive patients, African-Americans and Caucasians realized comparable benefit from either the addition of chemotherapy or tamoxifen to surgery alone or the addition of chemotherapy to tamoxifen. In summary, African-American women and Caucasian women who were diagnosed at a comparable disease stage and were similarly treated tended to experience similar breast cancer prognosis. However, a mortality deficit persisted for African-American women relative to Caucasian women, which may be in part due to greater mortality from noncancer causes among African-Americans. Benefit from systemic adjuvant therapy for recurrence and mortality reduction was comparable between African-Americans and Caucasians. This study and investigations in other health-care settings suggest that African-American women and Caucasian women with breast cancer derive a similar benefit from systemic adjuvant therapy when it is administered in accordance with their clinical and pathologic disease presentation.

Differences in breast cancer prognosis among African-American and Caucasian women

This review explores factors potentially contributing to the disparity in survival after breast cancer between African-American and Caucasian women in the United States. A number of factors have been implicated as the cause of poorer survival for black women, including clinical and pathologic features of the disease that are indicative of poor prognosis, economic resource inequities, and differences in treatment access and efficacy. The latter is explored in detail using data from the National Surgical Adjuvant Breast and Bowel Project (NSABP), a nationwide multicenter clinical trials group for breast and colorectal cancers. Key studies into the disparity in breast cancer survival are reviewed according to proposed principal determinants of poorer outcome for black women. Results among black and white women participating in several randomized NSABP clinical trials are also presented. Primary endpoints in those studies were clinical and pathologic disease characteristics at study entry, time to disease progression or new cancers, and total survival time after breast cancer diagnosis and treatment. In most studies reported in the literature, the primary explanatory factor alone, such as stage of disease at diagnosis, did not fully account for differences in outcome between groups; when additional factors were taken into account, however, prognoses became more similar. Results from the NSABP clinical trials similarly indicated that when stage of disease and treatment were comparable, outcomes for blacks did not differ markedly from those of whites. In summary, black women, diagnosed at comparable disease stage as white women and treated appropriately, tend to experience similar breast cancer prognoses and survival. However, important clinical and pathologic disease characteristics may continue to place certain women at increased risk of poorer outcome, and warrant continued study. The opportunity for increased clinical trial participation by black women is encouraged.

Outcomes among African-Americans and Caucasians in colon cancer adjuvant therapy trials: findings from the National Surgical Adjuvant Breast and Bowel Project

BACKGROUND

African-Americans generally have lower survival rates from colon cancer than Caucasian Americans. This disparity has been attributed to many sources, including diagnosis at later disease stage and other unfavorable disease features, inadequate treatment, and socioeconomic factors. The randomized clinical trial setting ensures similarity in disease stage and a uniform treatment plan between blacks and whites. In this study, we evaluated survival and related end points for African-American and Caucasian patients with colon cancer participating in randomized clinical trials of the National Surgical Adjuvant Breast and Bowel Project (NSABP) to determine whether outcomes were less favorable for African-Americans.

METHODS

The study included African-American (n = 663) or Caucasian (n = 5969) patients from five serially conducted, randomized clinical trials of the NSABP. We compared recurrence-free survival, disease-free survival (recurrence, new primary cancer, or death), and survival (death from any cause) between blacks and whites by using statistical modeling to account for differences in patient and disease characteristics between the groups. Statistical tests were two-sided.

RESULTS

Dukes' stage and number of positive lymph nodes were remarkably similar between African-American and Caucasian patients in each trial. Over all trials combined, an 8% (95% confidence interval [CI] = -6% to 25%; P =.27) excess risk of colon cancer recurrence that was not statistically significant was observed for blacks. A greater disparity in survival was seen, with blacks experiencing a statistically significant 21% (95% CI = 6%-37%; P =.004) greater risk of death. Treatment efficacy appeared similar between the groups.

CONCLUSIONS

While the overall survival prognosis was less favorable for African-Americans compared with Caucasians in these trials, other outcomes measured were considerably more similar than those seen in the population at large, suggesting that earlier detection and adjuvant therapy could appreciably improve colon cancer prognosis for African-Americans. Continued investigations into causes of the deficits noted are warranted.

Early stopping of a clinical trial when there is evidence of no treatment benefit: protocol B-14 of the National Surgical Adjuvant Breast and Bowel Project

Although several randomized clinical trials in the 1980s indicated a benefit from the use of tamoxifen in the treatment of early-stage breast cancer, questions have remained regarding the optimal duration of drug administration. In 1982, the National Surgical Adjuvant Breast and Bowel Project (NSABP) initiated a randomized trial to compare 5 years of tamoxifen to placebo among breast cancer patients with estrogen receptor-positive tumors and no evidence of axillary node involvement. By 1987, evidence of a substantial benefit for tamoxifen led the NSABP to extend this trial to determine whether longer duration tamoxifen therapy would be additionally beneficial. This study randomized patients who had completed 5 years of tamoxifen free of breast cancer recurrence or other events to either tamoxifen or placebo for an additional 5 years. By 1994, 1172 women had entered the study and accrual was closed. In late 1995, the trial was terminated on the basis of interim findings indicating that a benefit for continuing tamoxifen would not be realized. The closure has prompted controversy among cancer researchers, because there are currently at least three tamoxifen duration trials in progress, whereas results from two other studies evaluating 5-year duration therapy versus longer therapy were recently published. Here, we provide details of the statistical rationale contributing to our decision to recommend early closure of the study. We then consider other possible approaches to assessing the appropriateness of early termination in the face of evidence against a benefit, including Bayesian methods, which can be used to incorporate a range of prior beliefs regarding the efficacy of a treatment with accruing information from the trial. We also briefly discuss results of the other published studies.

Prognosis among African-American women and white women with lymph node negative breast carcinoma: findings from two randomized clinical trials of the National Surgical Adjuvant Breast and Bowel Project (NSABP)

BACKGROUND

A disparity in breast carcinoma survival between African-American and white women has been noted over the past several decades. A major factor implicated in this disparity is stage of disease at diagnosis. In this study, survival and related endpoints were examined among African-American women and white women with lymph node negative breast carcinoma who participated in two randomized clinical trials of the National Surgical Adjuvant Breast and Bowel Project (NSABP).

METHODS

Patients from two studies, one conducted among patients with estrogen receptor (ER) negative tumors and the other among patients with ER positive tumors, were included. Study goals were to determine whether African-Americans and whites had comparable outcomes, accounting for ER status and differences in patient characteristics at diagnosis, and to determine whether treatment response was similar for African-Americans and whites.

RESULTS

Five-year survival rates were 83% for African-Americans and 85% for whites among ER negative patients, and 93% for African-Americans and 92% for whites among ER positive patients. Rates of disease free survival (DFS) (i.e., time to disease recurrence, second primary cancer, or death) were 71% for African-Americans and 74% for whites at 5 years among ER negative patients, and 81% for African-Americans and 80% for whites among ER positive patients. African-Americans tended to have less favorable baseline prognostic characteristics. Adjusted relative risk (RR) estimates indicated similar prognosis for African-Americans compared with whites for mortality (African-American/white RR = 1.02 with 95% confidence interval [CI], 0.66-1.56 among ER negative patients; RR = 1.14 with 95% CI, 0.84-1.54 among ER positive patients) and DFS (RR = 0.98 with 95% CI, 0.70-1.37 for ER negative patients; RR = 0.96 with 95% CI, 0.75-1.22 for ER positive patients). Estimated percent reductions in DFS events for patients receiving adjuvant therapy were 32% for ER negative African-Americans, 36% for ER negative whites, 20% for ER positive African-Americans, and 39% for ER positive whites.

CONCLUSIONS

African-American and white patients with localized breast carcinoma had similar outcomes and benefited equally from systemic therapy. These results suggest that early detection and appropriate therapy among African-American patients could result in a reduction in the current disparity in breast carcinoma mortality between African-Americans and whites.

Methods for bounding the marginal survival distribution

For time to event data with many potential failure types, one cannot uniquely determine the distribution of time to a specific event type, or marginal survival distribution, in the case where event types are mutually exclusive. In this paper we discuss several methods for estimating functions that bound the non-identifiable marginal survival distribution in the competing risks problem. We compute and compare bounds for data simulated from two bivariate survival distributions. Results show that the methods provide a suitable estimate of the marginal survival probability when one has specified dependence correctly. Data from a large clinical trial for breast cancer illustrate the methods.

Contamination of individuals by radon daughters: a preliminary study

Body radon daughter contamination reflects relative individual respiratory exposures to radon daughters; counts can be related both to household radon levels and to lung cancer risk factors such as sex and tobacco smoking. Radon daughters were counted by gamma spectroscopy from 180 adult residents of eastern Pennsylvania. A seven-position, 35-min scan was conducted in a mobile body counter, generally during afternoon or evening hours. Track-etch detectors for household radon were distributed, and were recovered from 80% of the subjects. Over 75% of the population had environmentally enhanced radon daughter contamination. House radon levels were strongly related, as anticipated, to radon daughter contamination in the 112 subjects for whom both sets of measurements were available (p less than .001); basement measurements were as strongly related to personal contamination as were living area measurements; bedroom measurements were slightly more strongly correlated. Both sex (p less than .02) and cigarette smoking (p less than .01) significantly modified the relationships, after nonlinear adjustment for travel times. Using a logarithmic model, a given house living-area radon level was associated in females with body contamination by radon daughters 2-3 times that in males. Nonsmokers had 2-4 times higher levels of contamination than smokers. Results are for the total of internal and external contamination, these being highly correlated in preliminary experiments. Time usage and activity patterns of the subjects are believed to be important in explaining these findings, and may become important variables in radon risk assessment.