Ascertaining cases of invasive breast cancer in the 45 and Up Study: a validation study.

Kemp A, Preen DB, Saunders C, Holman CDJ, Bulsara M, Rogers K, Roughead EE.

Background

• Routinely-collected and self-reported health data are increasingly used to identify health status and service use

• State-based cancer registries are considered the ‘gold standard’ for identifying breast cancer cases for research purposes o However researchers conducting survey-based studies or

working with other datasets (e.g. hospital data) may need to identify cases without linkage to a cancer registry

o ‘Temporary’ access problems with cancer registrations in New South Wales (NSW)

Background continued

• Larger program of work examining use of prescription hormone therapies for invasive breast cancer in Australian practice (e.g. tamoxifen)

• Planned to identify cases of invasive breast cancer through the NSW Cancer Registry o Power calculations based on cases diagnosed 2003-2009

• We received all the datasets needed for the study except Cancer Registry records for 2009

• Can we ascertain 2009 cases of invasive breast cancer using information from the other available datasets?

Objective

• To determine the accuracy of hospital and outpatient services, prescription claims, and self-report for breast cancer in identifying cases of invasive breast cancer on the NSW Cancer Registry

Data sources

• NSW Cancer Registry (gold standard) o date of diagnosis for all invasive breast cancers in NSW

between 1 July 2004 to 31st December 2008

• 45 and Up Study baseline data o self-reported demographic and clinical information

• NSW Admitted Patients Data Collection o hospital separations for all public and private hospitals

• Pharmaceutical Benefits Scheme o claims for government-subsidised dispensed prescription

medicines • Medicare Benefits Schedule

o claims for government-subsidised outpatient procedures and procedures in private hospitals

Breast cancer ‘flags’

• Hospital diagnosis of invasive breast cancer o ≤ 6 months of diagnosis

• Breast cancer surgery o ≤12 months of diagnosis o mastectomy or lumpectomy

• Prescriptions dispensed o ≤18 months of diagnosis o tamoxifen, toremifene, anastrazole, exemestane, letrozole,

goserelin, trastubumab, lapatinib • Breast radiotherapy

o ≤18 months of diagnosis • Self-reported diagnosis breast cancer and age at diagnosis

o within 12 months of date of diagnosis o analysis restricted to self-reports before January 2006

Analyses

• Cases of invasive breast cancer recorded on the Cancer Registry during the study period were compared with flagged (suspected) cases

• Comparison included o flags from individual datasets (e.g. hospital diagnosis) o clinically meaningful combinations of flags (e.g. hospital

diagnosis and a dispensed medicine for breast cancer) • For each flag/s we calculated:

o positive predictive value (PPV) o sensitivity o Specificity

• We sought flags with high PPV (>90%) and within that, the highest specificity

Results

• Of 143,010 women in the 45 and Up Study, 2661 (1.9%) had a recorded invasive breast cancer on the Cancer Registry during the study period o 681 occurred between 1 July 2004 and 31st December

2005 (this subgroup was compared against self-reported breast cancer)

Results from individual datasets PPV Sensitivity Specificity

45 and Up Study baseline survey

Self-reported diagnosis (12 month window)

40.9% 73.0% 99.5%

Hospital data Inpatient primary diagnosis 80.3% 85.2% 99.7%

Lumpectomy 99.3% 61.3% 99.9%

Mastectomy 99.2% 35.2% 99.9%

Lumpectomy OR mastectomy 99.2% 86.3% 99.9%

Results from individual datasets PPV Sensitivity Specificity

45 and Up Study baseline survey

Self-reported diagnosis (12 month window)

40.9% 73.0% 99.5%

Self-reported diagnosis 72% of the ‘false positives’ had a record on the Cancer Registry for an earlier period

Hospital data Inpatient primary diagnosis 80.3% 85.2% 99.7%

Lumpectomy 99.3% 61.3% 99.9%

Mastectomy 99.2% 35.2% 99.9%

Lumpectomy OR mastectomy 99.2% 86.3% 99.9%

Results from individual datasets PPV Sensitivity Specificity

45 and Up Study baseline survey

Self-reported diagnosis (12 month window)

40.9% 73.0% 99.5%

Self-reported diagnosis 72% of the ‘false positives’ had a record on the Cancer Registry for an earlier period

Hospital data Inpatient primary diagnosis 80.3% 85.2% 99.7%

Lumpectomy 99.3% 61.3% 99.9%

Mastectomy 99.2% 35.2% 99.9%

Lumpectomy OR mastectomy 99.2% 86.3% 99.9%

Results from individual datasets

PPV Sensitivity Specificity

Pharmaceutical Benefits Scheme

Any dispensed medicine 88.5% 68.5% 99.9%

Medicare Benefits Schedule

Breast radiotherapy 95.8% 57.9% 99.9%

Results from 45 and Up Study, MBS and PBS data package

PPV Sensitivity Specificity

Breast radiotherapy AND dispensed medicine

95.8% 41.1% 99.9%

Breast radiotherapy OR dispensed medicine

89.9% 85.3% 99.9%

Breast radiotherapy AND self-reported diagnosis

70.2% 28.3% 99.9%

Breast radiotherapy AND dispensed medicine AND self-reported diagnosis

68.4% 19.4% 99.9%

(Breast radiotherapy OR dispensed medicine) AND self-reported diagnosis

67.8% 56.8% 99.9%

Breast radiotherapy OR dispensed medicine OR self-reported diagnosis

24.9% 94.1% 98.6%

Results from 45 and Up Study, MBS and PBS data package

PPV Sensitivity Specificity

Breast radiotherapy AND dispensed medicine

95.8% 41.1% 99.9%

Breast radiotherapy OR dispensed medicine

89.9% 85.3% 99.9%

Breast radiotherapy AND self-reported diagnosis

70.2% 28.3% 99.9%

Breast radiotherapy AND dispensed medicine AND self-reported diagnosis

68.4% 19.4% 99.9%

(Breast radiotherapy OR dispensed medicine) AND self-reported diagnosis

67.8% 56.8% 99.9%

Breast radiotherapy OR dispensed medicine OR self-reported diagnosis

24.9% 94.1% 98.6%

Results from hospital, 45 and Up Study, MBS and PBS datasets

PPV Sensitivity Specificity

(Lumpectomy or mastectomy) AND diagnosis of invasive breast cancer AND dispensed medicine

99.4% 56.7% 99.9%

(Lumpectomy or mastectomy) AND (diagnosis of invasive breast cancer OR breast radiotherapy)

96.8% 91.6% 99.9%

(Lumpectomy or mastectomy) AND (diagnosis of invasive breast cancer OR dispensed medicine)

91.2% 93.7% 99.9%

(Lumpectomy or mastectomy) AND (diagnosis of invasive breast cancer OR breast radiotherapy OR dispensed medicine)

90.8% 96.8% 99.9%

Results from hospital, 45 and Up Study, MBS and PBS datasets

PPV Sensitivity Specificity

(Lumpectomy or mastectomy) AND diagnosis of invasive breast cancer AND dispensed medicine

99.4% 56.7% 99.9%

(Lumpectomy or mastectomy) AND (diagnosis of invasive breast cancer OR breast radiotherapy)

96.8% 91.6% 99.9%

(Lumpectomy or mastectomy) AND (diagnosis of invasive breast cancer OR dispensed medicine)

91.2% 93.7% 99.9%

(Lumpectomy or mastectomy) AND (diagnosis of invasive breast cancer OR breast radiotherapy OR dispensed medicine)

90.8% 96.8% 99.9%

Strengths and weaknesses

• Strengths o Large, heterogeneous sample of women o Complete capture for all public and private inpatient

diagnoses and surgeries, subsidised outpatient procedures and medicines

• Weaknesses o We could not identify how many false positives were DCIS

vs. not breast cancer at all o The flags we have identified may not predict invasive

breast cancer as well in younger women o Validity of the flags examined here may change over time

with shifts in health service use

Conclusions

• Invasive breast cancer can be accurately ascertained through administrative datasets other than the Cancer Registry

• The most useful flags will depend on the research question and available datasets

• Self report with date restriction had moderate sensitivity and low PPV, however specificity was very high o Suitable for excluding cases of breast

cancer from a study sample

Conclusions

• We had access to 45 and Up Study baseline survey, hospital, MBS, and PBS data and needed to identify a sample

• The most useful flag or this purpose: o (Lumpectomy or mastectomy) AND (primary diagnosis of

invasive breast cancer or breast radiotherapy) o 97% of those identified are true positives o 92% of cases on the Cancer Registry

are identified

Acknowledgements

• Participants of the 45 and Up Study • The 45 and Up Study is managed by the Sax Institute in

collaboration with: • Cancer Council New South Wales (major partner) • National Heart Foundation of Australia (NSW Division) • NSW Ministry of Health • beyondblue: the national depression initiative • Ageing, Disability and Home Care NSW Family and

Community Services • Australian Red Cross Blood Service • UnitingCare Ageing

Acknowledgements

• Staff at the Centre for Health Record Linkage • Other data custodians:

o NSW Ministry of Health o Commonwealth Department of Human Services o NSW Cancer Institute

• The project was funded by: o Cancer Australia o National Breast Cancer Foundation

Questions