Abstract P5-13-12: Breast cancer in Colombia: A growing challenge for the health care system

INTRODUCTION

Colombia has a population of roughly 49 million people of predominantly Mestizo ethnicity. Cancer has become a growing public health problem in Colombia with nearly 71,000 newly diagnosed malignant tumors per year. It is expected that by 2035, 150,000 new cases of cancer will be diagnosed, making Colombia an intermediate country with regards to global cancer incidence according to IARC.

METHODS

Epidemiological data on breast cancer is scarce and varied due to multiple sources of information. These numbers are obtained thru population-based cancer registries that represent 4 distinct regions of the country. Other data originate from non-governmental institutions and healthcare providers within Colombia. The Colombian National Cancer Institute publishes a Cancer Mortality Atlas annually.

RESULTS

Local cancer registries have shown increases in breast cancer incidence in Colombia. In 2007, age-standardized incidence rate was 27.8 per 100,000 persons increasing to 49.7 cases per 100,000 persons in 2012. Approximately, 2200 women die every year in Colombia due to breast cancer with rates increasing historically, but now are stabilizing. Advanced breast cancers are most frequently found among women without health insurance, while early breast cancers are usually found among working women and those covered by private health insurance. Early breast cancer screening was made mandatory as public policy in the year 2000. However, only 30% of health care coverage was reported, translating to very low coverage by opportunistic screening programs with only 33% of women having had a mammography. In 2012, a National Cancer Control Plan was planned and implemented. It aims to increase early stage cancer diagnosis, increase biannual screening coverage, and guarantee timely access to diagnosis and treatment. A national health survey in 2015 showed only 48% of women had an annual mammographic screening. Multiple disparities have been found with regards to screening and early diagnosis such as economic strata, health insurance coverage, origin, and accessibility. Specifically, data shows that 23% needed to travel in order to obtain access to mammography. Often it is necessary for some patients to sue healthcare insurance systems to obtain specific health care, causing an increase in time to diagnosis and treatment. In 2016, on average a 90-day period was reported from time of onset of symptoms to suspected diagnosis of breast cancer, while the time to the initiation of treatment was 100 days for chemotherapy and close to 120 days for surgery.

DISCUSSION

These data serve to impact the landscape of breast cancer and improve patient outcomes in Colombia. While the National Cancer Plan has led to major changes, a big challenge remains related to the delays between suspicion of breast cancer and diagnosis and treatment. Quality of care provided by private and public insurance administrators is also of concern. General practitioners should receive more detailed training in breast cancer detection and management. The healthcare system should provide quality cancer care with urgent improvement in mammography, especially in more rural areas. Widely, more timely and appropriate follow-up is needed.

Citation Format: Duarte C, Salazar A, Strasser-Weippl K, de Vries E, Wiesner C, Krush L, Goss PE. Breast cancer in Colombia: A growing challenge for the health care system [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P5-13-12.

Abstract P4-14-03: Influence of competing risks of death on the interpretation of adjuvant endocrine therapy trials for breast cancer

Background: Early stage, hormone sensitive breast cancer is associated generally with a good prognosis, with only a minority of patients expected to die of breast cancer. Death from causes other than breast cancer can dilute the patients at risk of breast cancer events and result in over-estimation of risk of recurrence and consequently the benefit from breast cancer therapy, a so-called immortal time bias. The MA.17R trial (Goss et al 2016) evaluated the role of extending adjuvant treatment with letrozole from 5 to 10 years. Here we determine the effect of analyzing the MA.17R trial using methods accounting for competing risks.

Methods: We compared conventional and competing risk methods for disease-free survival (DFS) and for distant recurrence-free survival (DRFS). In Kaplan-Meier analyses death from any cause was considered an event while cumulative incidence functions (CIFs) assumed death without recurrence to be a competing risk. The complement of the survival function (one minus the survival function) was used to estimate incidence of the primary event of interest. This was compared to estimates obtained using CIFs accounting for the occurrence of competing events.

Results: Non-breast cancer death was the most common event defining DFS and DRFS. Over the course of follow-up, there was increasing discrepancy between the risk of disease recurrence measured using Kaplan-Meier and CIF. Among letrozole treated patients the estimated distant recurrence at 5 years of follow-up was 5.4% using CIF and 9.6% using Kaplan-Meier. At 10 years of follow-up, the estimated distant recurrence was 8.4% using CIF and 20.0% using Kaplan-Meier. Similar results were observed for the placebo group (8.5% vs 12.1% at 5 years and 14.8% vs 27.3% at 10 years), and in patients with baseline cardiovascular disease (see Table). Benefit from letrozole on DFS and DRFS was greater when accounting for competing risk (hazard ratio [HR] for DFS 0.66, 95%CI 0.48-0.90; DFRS HR 0.75, 0.50-1.14) compared to the conventional method (DFS HR 0.79, 0.62-0.99; DRFS HR 0.91, 0.70-1.18). In women with baseline cardiovascular risk, the benefits of extended adjuvant letrozole when considering competing risk (DFS HR 0.38, 0.16-0.89; DRFS HR 0.46, 0.16-1.35) were also greater than those observed in the conventional analysis (DFS HR 0.55, 0.32-0.93; DRFS HR 0.59, 0.33-1.04). Treatment with extended letrozole did not influence non-breast cancer death in women who died with disease recurrence (HR 1.06, 0.74 -1.50) or in those with competing risk or censored from the analysis (HR 1.05, 0.73 -1.49).

Conclusion: Over the course of follow-up, estimates of DFS and DRFS differ increasingly if measured using Kaplan-Meier or CIF, with CIF estimates of risk being substantially lower. Using a competing risk model, the reduction in distant recurrence at 8 years with extended letrozole is less than 1%. Additional competing risk analyses of the MA.17 (Goss 2006) and MA.27 (Goss 2013) trials are ongoing.

Cumulative incidence of disease recurrence in patients with baseline cardiovascular riskTime (years)CIF (%)1-KM (%)Letrozole11.51.534.46.555.813.8Placebo13.53.538.311.8512.520.3

Citation Format: Ethier J-L, Parulekar W, Shepherd L, Summers L, Strasser-Weippl K, Tu D, Amir E. Influence of competing risks of death on the interpretation of adjuvant endocrine therapy trials for breast cancer [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr P4-14-03.

Outcomes in women with invasive ductal or invasive lobular early stage breast cancer treated with anastrozole or exemestane in CCTG (NCIC CTG) MA.27

BACKGROUND

Histological subtype, (invasive ductal breast cancer (IDBC)/invasive lobular breast cancer (ILBC)), might be a marker for differential response to endocrine therapy in breast cancer.

METHODS

Clinical trial MA.27 compared 5 years of adjuvant anastrozole or exemestane in postmenopausal patients with hormone receptor positive early breast cancer. We evaluated IDBC versus ILBC (based on original pathology reports) as predictor for event-free survival (EFS) and overall survival (OS).

RESULTS

A total of 5709 patients (5021 with IDBC and 688 with ILBC) were included (1876 were excluded because of missing or other histological subtype). Median follow-up was 4.1 years. Overall, histological subtype did not influence OS or EFS (HR (hazard ratio) 1.14, 95% confidence interval (CI) [0.79-1.63], P = 0.49 and HR 1.04, 95% CI [0.77-1.41], P = 0.81, respectively). There was no significant difference in OS between treatment with exemestane versus treatment with anastrozole in the IDBC group (HR = 0.92, 95% CI [0.73-1.16], P = 0.46). In the ILBC group, a marginally significant difference in favour of treatment with anastrozole was seen (HR = 1.79, 95% CI [0.98-3.27], P = 0.055). In multivariable analysis a prognostic effect of the interaction between treatment and histological subtype on OS (but not on EFS) was noted, suggesting a better outcome for patients with ILBC on anastrozole (HR 2.1, 95% CI [0.99-4.29], P = 0.05). After stepwise selection in the multivariable model, a marginally significant prognostic effect for the interaction variable (treatment with histological subtype) on OS (but not on EFS) was noted (Ratio of HR 2.1, 95% CI [1.00-4.31], P = 0.05).

CONCLUSION

Our data suggest an interaction effect between treatment and histology (P = 0.05) on OS. Here, patients with ILBC cancers had a better OS when treated with anastrozole versus exemestane, whereas no difference was noted for patients with IDBC.

CLINICAL TRIAL INFORMATION

NCT00066573.