Effects of multidisciplinary team working on breast cancer survival: retrospective, comparative, interventional cohort study of 13 722 women
Effects of multidisciplinary team working on breast cancer survival: retrospective, comparative, interventional cohort study of 13 722 women by Eileen Kesson and colleagues (BMJ 2012;344:e2718)
Objectives—To describe the effect of multidisciplinary care on survival in women treated for breast cancer.
Design—Retrospective, comparative, non-randomised, interventional cohort study.
Setting NHS hospitals, health boards in the west of Scotland, UK.
Participants—14 358 patients diagnosed with symptomatic invasive breast cancer between 1990 and 2000, residing in health board areas in the west of Scotland. 13 722 (95.6%) patients were eligible (excluding 16 diagnoses of inflammatory cancers and 620 diagnoses of breast cancer at death).
Intervention—In 1995, multidisciplinary team working was introduced in hospitals throughout one health board area (Greater Glasgow; intervention area), but not in other health board areas in the west of Scotland (non-intervention area).
Main outcome measures—Breast cancer specific mortality and all cause mortality.
Results—Before the introduction of multidisciplinary care (analysed time period January 1990 to September 1995), breast cancer mortality was 11% higher in the intervention area than in the non-intervention area (hazard ratio adjusted for year of incidence, age at diagnosis, and deprivation, 1.11; 95% confidence interval 1.00 to 1.20). After multidisciplinary care was introduced (time period October 1995 to December 2000), breast cancer mortality was 18% lower in the intervention area than in the non-intervention area (0.82, 0.74 to 0.91). All cause mortality did not differ significantly between populations in the earlier period, but was 11% lower in the intervention area than in the non-interventional area in the later period (0.89, 0.82 to 0.97). Interrupted time series analyses showed a significant improvement in breast cancer survival in the intervention area in 1996, compared with the expected survival in the same year had the pre-intervention trend continued (P=0.004). This improvement was maintained after the intervention was introduced.
Conclusion—Introduction of multidisciplinary care was associated with improved survival and reduced variation in survival among hospitals. Further analysis of clinical audit data for multidisciplinary care could identify which aspects of care are most associated with survival benefits.
Why do the study?
Breast cancer is the most common cancer of women worldwide. This makes the subject of great importance to most doctors. Oncological patients have complex needs and are managed by different specialists including surgeons, radiologists, medical and clinical oncologists, pathologists, clinical nurse specialists, and administrative staff.
Specialist teams—groups of doctors including specialised radiologists, oncologists, histopathologists, surgeons, and clinical nurse specialists—were introduced after observational evidence of better outcomes for patients treated by specialists for various common cancers. This included an 11-17% reduction in risk of death among women treated for breast cancer by specialist surgeons. But it is less clear that multidisciplinary care improves survival compared with smaller units. Intuitively, it seems that doctors working in isolation outside a multidisciplinary team (MDT) are limiting the scope of the care they can deliver. But does this equate to measurable differences in patient outcomes?
This study aims to answer that question. In the 1990s, variations in the survival of patients with breast cancer in Scotland were reported to the director of public health. The mortality rate differed from region to region. Did the introduction of multidisciplinary teams in the Glasgow area in the mid 1990s improve the outcomes in patients with breast cancer? This study aims to answer that question. It compared survival in the Glasgow area (patients managed in a multidisciplinary team) to other areas in the West of Scotland (patients not managed in a multidisciplinary team). The authors looked back at the survival data and compared them. So this is a retrospective study.
Research questions are generally best answered by systematic reviews. However, in previous systematic reviews in this area, the study populations contained variations in patient populations that confounded the results. Limitations in previous studies included a precise and consistent definition of what a multidisciplinary team actually consisted of, bias in reporting outcomes, and a lack of adjustment for confounding factors. The authors of this study aimed to rectify this by carefully defining what a multidisciplinary team consisted of and by using similar patient populations.
What did the authors do?
The authors used the Scottish Cancer registry to extract data from the records of patients with symptomatic invasive breast cancers. This is linked to the death records from the General Register Office for Scotland, making the survival data robust.
The patients were grouped into four age categories, to allow the calculation of any prognostic differences between age groups.
One of the factors that made this study different from previous ones was an explicit description of what made up a multidisciplinary team. A key factor is patient throughput. Each MDT saw more than 50 operative cases of invasive breast cancer each year. The authors defined a multidisciplinary team as having the following characteristics:
- Comprises specialist surgeons, pathologists, oncologists, radiologists, and specialist nurses
- Works to evidence based guidelines
- Meets weekly to discuss patient management and results
- Records outcomes and discusses the audit results with the director of public health.
The authors appreciate that healthcare outcomes are affected by socioeconomic status, and so gave patients a deprivation category score based on their postcode. Without accounting for this, a huge potential confounder would have adversely affected the interpretation of these results.
Data were obtained from groups who have been exposed, or not exposed, to multidisciplinary team care, according to their region. The authors chose to have two pairs of parallel groups for comparison, one looking at survival from January 1990 to September 1995 and the other from October 1995 to December 2000. This is a good way of reducing the effect of the improvement in survival that may have occurred over time rather than from the introduction of MDTs. The advantages of observational cohort study designs are that they are ethically safe, subjects can be matched, and it is easy to establish the timing and sequence of events. No allocation of exposure is made by the researcher. The limitations of cohort studies are difficulties in blinding or identifying controls, hidden confounders, and a lack of randomisation.
The authors used statistical analyses to compare the difference in survival trends between the intervention and non-intervention groups. They then adjusted the survival for age, deprivation, and year of incidence, and carried out another analysis to examine differences in survival between the two groups.
Funnels plots were then used to graphically illustrate survival in the intervention and non-intervention groups (figure). 1
What did the study find?
Before multidisciplinary care, breast cancer mortality was 11% higher in the Greater Glasgow health board, compared with the rest of the West of Scotland. After 1995, when multidisciplinary teams were introduced into the Greater Glasgow health board area, breast cancer mortality reduced by 18%. Hence, the introduction of modern cancer treatment teams led to a direct improvement. When a subgroup of patients over 80 was separately analysed, this difference was seen to an even greater degree.
The authors attempted to assess socioeconomic circumstances in case areas poorer health outcomes were explained bydeprivation. They did indeed find higher mortality in the lower socioeconomic groups both before and after MDTs. That is why it was so important to account for this.
The funnel plot shows that the number of patients diagnosed per hospital increased in the intervention group after 1995. This is a positive outcome. Additionally, one outlier was noted in the non-intervention group, and none in the intervention group. Funnel plots can be used to identify hospitals that fall outside the expected survival range, and an assessment made of their services and patient population. The introduction of multidisciplinary teams reduced the numbers of hospitals treating breast cancer, and reduced the variation in survival rates among these.
What are the strengths and limitations of this study?
The authors comment that there were no other ways to do this study, but the study design is not deemed to be the ideal model. It was not a double blinded study—that is, the researcher who did the survival comparison knew which hospitals were in the intervention group and which were not—and potential bias was possible secondary to this. This leads the reader to think about what contribution to the results the confounders and selection biases would have made.
The biggest strengths of the study are accounting for the confounders by comparing two groups at the same time. This was done via geographical separation, which in itself can also introduce a further set confounding factors. Again, the authors tried to account for this by assessing socioeconomic status. But, as they state, this was not always measured precisely, but inferred from postal addresses. Furthermore, source data depend on accurate coding (into a disease code) from the hospital that reviewed the patient, which was not always the case. This effect was mitigated against by using Scottish Cancer Registry data. Unfortunately, these data are not always comprehensive, and can omit important, cancer specific prognostic information. Additionally, patients who were diagnosed via the National Breast Cancer screening pathways were excluded from this study. This might give an overly pessimistic view of the outcomes, because this population might have a more advanced stage of disease compared to a patient who has breast cancer diagnosed via screening.
Although the authors state in the introduction this was an interventional study, as they did not perform the intervention but rather reported on the differences in outcome, it could be more strictly defined as an observational, rather than interventional, study.
What does this study mean?
The authors conducted a retrospective cohort study on survival differences before and after multidisciplinary teams were introduced by taking advantage of regional differences in care policy. This study has demonstrated two important concepts; people in deprived areas do not fare as well in health terms as those in affluent areas; and involvement of a multidisciplinary team in the management of breast cancer saves lives.Rej Bhumbra, editorial registrar, BMJ
Correspondence to: email@example.com
Competing interests: None declared.
Provenance and peer review: Commissioned; not externally peer reviewed.
- Hong NJL, Wright F, Gagliardi A, Paszat L. Examining the potential relationship between multidisciplinary cancer care and patient survival: an international literature review. J Surg Oncol 2010;102:125-34.
Cite this as: Student BMJ 2013;21:f362