Journal of the New Zealand Medical Association, 10-August-2012, Vol 125 No 1359
The National Breast Cancer Audit (NBCA) was initiated in 1998 and collects data on the surgical care of early breast cancer patients in Australia and New Zealand. The audit is managed by the Australian Safety and Efficacy Register of New Interventional Procedures-Surgical (ASERNIP-S) Program, being part of the Research, Audit and Academic Surgery Division of the Royal Australasian College of Surgeons (RACS). This is a secure online data entry system and participation in the NBCA is a requirement for full membership of the newly formed Breast Surgeons’ Society of Australia and New Zealand (BreastSurgANZ).
Participating surgeons are able to obtain reports about their practice standards and compare it with minimum thresholds for defined key performance indicators (KPI). Since the launch of the online data entry system in May 2004, the percentage of NBCA data submitted by New Zealand surgeons has increased from 20% to 27%.1
Breast Screen Aotearoa (BSA) is a national breast screening program that offers free screening mammograms to all New Zealand women aged 45 to 69 years with no symptoms of breast cancer. BSA organises breast screening services throughout New Zealand and it is part of the National Screening Unit of the Ministry of Health.
To ensure that BSA program is working well, BSA services are required to comply with the National Policy and Quality Standards set by BSA. The Independent Monitoring Group reports to the National Screening Unit every 6 months on how well each BSA service is meeting the quality standards. Regular audits of BSA services are also conducted to ensure this.2 It is a requirement of surgeon accreditation to BSA that the surgeon submits all their breast cancer cases to the NBCA.
This audit is supported by BSA in order to obtain audit data for women in New Zealand with screen detected cancers. This paper is based on the first such report and compares the presenting features and management of screen detected cancers with symptomatic for New Zealand women. This paper aims to examine invasive cancers only and a separate paper looks at Ductal Carcinoma In Situ.
A Structured Query Language (SQL) query was written to extract New Zealand data with a diagnosis date of 2008 from the NBCA online database on 01 April 2010. In addition to this, data was included from Auckland Breast Cancer Register for cases diagnosed between July and December 2008. This was distributed across the BSA and non BSA groups. This dataset was scheduled to be uploaded into the NBCA database through the institutional upload program later in 2010.
Percentage case volumes for New Zealand data have been reported by referral source under the following headings : background information (such as referral source, public versus private treatment, age of patients), invasive tumour characteristics (histological type, size and grade distribution), breast surgery treatment (breast conserving surgery or mastectomy with or without breast reconstruction), axillary surgery treatment, margins of excision for breast surgery, rates and types of re-operation, hormone receptor status, endocrine therapy, rates of chemotherapy and radiotherapy prescription.
The number of cases reported from Breast Screen Aotearoa (BSA) and other referral sources for each category were compared using Chi-squared test using the Statistical Package for Social Sciences software (SIPSS Inc., Chicago, IL, USA). A statistical significance level of P<0.05 was used.
There were 9718 cases reported to the NBCA in 2008 and 2371 of there cases were from New Zealand. Out of the 259 surgeons who contributed to the audit in 2008, 70 were from New Zealand. As approximately 2600 cases of breast cancer are diagnosed in NZ each year, this figure indicates that approximately 90% of NZ women with newly diagnosed breast cancer are being entered on the audit. The remaining 10% may include advanced breast cancer which is not collected by the NBCA, as well as a small number of cases treated by New Zealand surgeons not participating in the audit.
The majority of breast cancer cases from New Zealand were referred as symptomatic from a GP (52%) and Breast Screen Aotearoa was the second most common referral source (37%). Patients referred from other sources include patients with screen detected cancers outside of BSA such as private screening. A very small number were referred from Breast Screen Australia.
See Table 1 for Referral source for New Zealand episodes.
Table 1. Referral source for New Zealand episodes
The majority (88%) of New Zealand breast cancer episodes were invasive. 78.49% of cases referred from BSA were invasive cases compared to 93.06% of non-BSA referrals. Almost all (97.37%) patients in the BSA group were within the screening age of 45–69 years.
The peak incidence (39.7% of 874) of patients in the BSA group were in the 51 to 60 year old age group. In the not BSA group, 52% of patients were in the 45 to 70 year age group with 22% of patients under 45 years of age and 26% of patients over the age of 70 years. All BSA patients were female and only 1% of non BSA patients were male. As expected, our policy is to invite all women to BSA, therefore there were no men in the BSA group.
Almost two-thirds (63%) of New Zealand patients received surgical care as a public patient with 70% of the BSA group looked after as public compared to 58% in the not BSA group.
The 12% of ductal carcinoma in situ cases reported by the NBCA, are excluded from the following results, which concentrate on invasive cancer only.
Invasive tumour characteristics—Most (80%) of the invasive tumours were Ductal Carcinoma Not Otherwise Specified (Table 2 Invasive Tumour Characteristics). Percentages of Invasive Lobular (15%, p=0.012) and Tubular (3%, p=0.001) were higher in the BSA group than in the not BSA group (11%, 1%). The percentage of patients with smaller tumours (15mm) was significantly higher in the BSA group (55%) than in the not BSA group (23%) (p=0.00).(Table 3 Size of invasive tumour).
There was a higher percentage of Grade 1 invasive tumours in the BSA group (37%) than in the non BSA group (19%) (Refer to Figure 1). Conversely, the percentage of Grade 3 tumours was higher in the non BSA group (39%) than in the BSA group (18%). There was no significant difference for the Grade 2 invasive tumours between BSA and not BSA groups.
Table 2. Type of invasive tumour by referral source†
† Tumour types were not known for 17 BSA and 20 not BSA patients.
Table 3. Size of invasive tumour in mm by referral source†
† Invasive tumour size was not known for 8BSA and 23 not BSA patients
Figure 1. Histological grade of invasive tumour by referral source†
† Histological grade of the invasive tumour were not known for 23 BSA and 36 not BSA patients.
For almost two-thirds of New Zealand patients (64% of 1475 cases), lymphatic vascular invasion (LVI) was absent (539 cases were excluded due to missing LVI information). The percentage of patients with lymphatic vascular invasion was lower in the BSA group (23% of 491 cases) than in the not BSA group (42% of 984 cases) (p=0.00).
A minority (4%) of invasive cancers in New Zealand were bilateral synchronous and there was no difference in the percentage of bilateral synchronous cancers between the patients from BSA (3.36%) and not BSA (3.75%) groups.
Majority of New Zealand patients were post-menopausal (1234 of 1960 or 63%). The percentage of premenopausal women was lower in the BSA group (18%) than in the not BSA group (35%) (p=0.00).
The proportion of peri-menopausal women in the BSA group was 10.7% and not BSA was 5.97% (p=0.00). Similarly, the proportion of post-menopausal women in BSA (71.03%) was higher than the not BSA group (58.73%) (p=0.00).
Most of the New Zealand patients (80% of 1975, 39 cases excluded due to missing information) had oestrogen receptor positive tumours, while 68% (out of 1965 cases, where 49 cases were excluded due to missing information) had progesterone receptor positive tumours.
The percentage of patients with oestrogen and progesterone receptor positive tumours were higher in the BSA group (89%, 78%) than in the not BSA group (76% 64%) (p=0.00). Human Epidermal Growth Factor Receptor (HER) 2 negativity was common in New Zealand patients with 86% (out of 637 cases) of BSA patients with HER 2 negative tumours compared to 81% (out of 1210 cases) of not BSA group (p=0.007, 167 cases were excluded due to missing HER2 data).
Breast surgery treatment—Breast conserving surgery (BCS) was more commonly undertaken for BSA patients (62%) compared not BSA patients (38%, p=0.00). More than half of not BSA patients had mastectomy (57%) as their first surgical treatment compared to 34% of BSA patients (p= 0.00).There were a small number of patients who had an open biopsy as their first operation (3% in BSA and 2 % in not BSA group). The re-operation rate for patients after BCS was 19% in BSA patients and 22% for not BSA patients.
Refer to Table 4 for further breast surgery after BCS. About 10% of patients in both groups required a re-excision, with a similar percentage requiring complete mastectomy.
Table 4. Further breast surgery after BCS for invasive cancer by referral source
The majority of New Zealand patients (84%) did not have breast reconstruction after mastectomy. Only 19% of BSA and 14% of not BSA patients had reconstruction after mastectomy for invasive cancer.
Margins—Most of the New Zealand patients (87%) had ≥2mm margin after surgery for invasive cancer. This margin is determined after all surgery is performed, and it includes either the circumferential or radial margin.
The percentage of patients with involved margin after surgery was low (3%) and was not significantly different between the BSA and not BSA groups. (Table 5 Margins for invasive cancer by referral source). Although data on circumferential versus vertical margins is collected, this was not analysed in the report.
Table 5. Margins of invasive cancer by referral source†
† Margin size was not known for 17 BSA and 20 not BSA cases.
Axillary surgery—Regardless of the tumour size, a higher percentage of BSA patients had sentinel node biopsy as their only axillary surgery (62% compared with 36% of not BSA) and a higher percentage of not BSA patients had Level 2 or Level 3 axillary clearance as their only axillary surgery (42% compared with 17% of BSA).
As expected from clinical practice guidelines, a higher percentage of patients had Level 2 or Level 3 axillary surgery for tumours greater than 3cm in size (71% compared with 25% of those ≤3cm).
Adjuvant therapies—Postoperative radiotherapy followed breast conserving surgery in 98% of patients in the BSA group and 92% of patients in not BSA group. There were 1062 of 1930(55%) patients with invasive cancer who had a mastectomy. Of women undergoing mastectomy, radiotherapy was prescribed in 25% of BSA patients and 49% of not BSA patients.
The proportion of patients with high risk invasive cancer who had mastectomy were 22% (230/1062). High risk invasive cancer was defined as invasive tumour greater or equal to 50mm or invasive tumour with 4 or more positive lymph nodes.
Most high-risk women (72% in BSA, 86% in not BSA) received post mastectomy radiotherapy. The percentage of patients receiving radiotherapy in high risk mastectomy group is much higher than in the whole mastectomy group (25% BSA, 49% not BSA).
Approximately 54% of all patients less than 70 years old were prescribed chemotherapy with a larger proportion in the not BSA population (67%) compared to BSA patients (35%) (p=0.000). Of those that were prescribed chemotherapy, 7% of BSA patients and 23% of not BSA patients were oestrogen and progesterone receptor negative.
This was statistically different between the two groups (p=0.001). There were only a small percentage of New Zealand patients greater than 70 years old who had chemotherapy treatment (13%).
Endocrine treatment was prescribed for the majority of New Zealand patients with oestrogen positive tumours (81%). In the BSA group, 76% of patients were prescribed endocrine treatment compared to 85% of patients in the not BSA group. Overall, there were very few patients who had ovarian ablation.
Refer to Table 6: Hormonal treatment for oestrogen positive cancer. A small percentage (8%) of patients with oestrogen negative tumours were also prescribed endocrine treatment.
Over two-thirds (67% of 261 cases) of patients with HER 2 positive, greater than 1 cm or node positive tumours received Herceptin (transtuzumab) treatment.
Table 6. Hormonal treatment for oestrogen positive invasive cancer†
† Endocrine treatment was not known for 24 BSA and 109 not BSA patients with oestrogen positive tumours.
The total number of breast cancer cases reported in New Zealand by the New Zealand Cancer Registry in 2007 was 2565.3 If this figure is similar to 2008 (which it is likely to be) this would indicate that surgeons performing breast cancer surgery are contributing over 90% of all NZ cases to the audit. This compares favourably to Australia whereby only about 45% of invasive breast cancer cases are entered into the NBCA.
The overall coverage or the percentage of women in the target age group for screening who have had a screening mammogram in the BSA program for the period of January to July 2009 is 58.9% in the 45–49 year age group and 65.2% for the 50–69 year age group. 4
The percentage of invasive cancers that was screen detected for 2008 was 37% This is higher than the annual percentage that is reported by the NBCA Australasia database from 1999 to 2004 which has been constant at about 20%. 5
The peak incidence of breast cancer in the BSA group occurred in the 51 to 60years age group. It is difficult to make comparisons of the age-related incidence of breast cancer as the data is not age standardised.
As expected, the majority of breast cancers that were screen detected were smaller (less than 20mm), of lower grade and had absence of lymphatic vascular invasion. This is consistent with the fact that screening tends to detect slower growing tumours, and accordingly, there is significantly more lobular and tubular cancers seen in the BSA group. At present, data is not available to define the number of screen detected cancers that were clinically palpable.
The minimal number of patients having an open biopsy indicates that the large majority of New Zealand patients are diagnosed pre-operatively. The rate of breast conserving surgery is comparable to Australasia at about 61% in the BSA group.
In the not BSA group, the rate of breast conserving surgery was lower at 38% with higher mastectomy rates. This is probably reflected by the larger tumours in the not BSA group. There are also other factors that may influence a higher mastectomy rate such as access to radiotherapy, rural hospital setting and it would also be interesting to examine if there was a surgeon bias. The NBCA report does not provide sufficient information to allow an assessment of these factors but may be addressed in future analyses.
The re-operation rate of about 19% in the period of this report is acceptable. There is wide range of re-operation rates reported in other studies ranging from 10% to as high as 30%. In a recently reported randomised controlled trial of Comparative Effectiveness of MRI in breast cancer (COMICE), the reported rate of re-operation was 19% and the addition of MRI to conventional triple assessment did not significantly reduce the re-operation rate. 6
The majority of the New Zealand patients had no reconstruction after mastectomy. Access to oncoplastic surgeons who perform breast reconstructions may influence the number of patients having reconstructions. Efforts are also being made to educate rural surgeons to consider early referrals for patients who may be suitable for breast reconstruction after mastectomy.
The higher rate of sentinel node biopsy in BSA patients is likely to reflect smaller cancers diagnosed in this group of patients. This is now considered accepted practice which is supported by several international trials as well as the Sentinel Node Axillary Clearance (SNAC) trial conducted in Australia and New Zealand.7 It has been shown to have a high sensitivity in predicting axillary lymph node status with a low false negative rate and has a significantly lower arm morbidity. The safety of performing a sentinel node biopsy in bigger tumours greater than 3 cm is yet to be proven and the SNAC 2 trial aims to examine this.
The majority of patients with tumours greater than 3 cm in this report have undergone at least a Level 2 or 3 axillary clearance consistent with the New Zealand Guidelines for Early Management of Breast Cancer.
Consistent with the NBCC Clinical Practice Guidelines for Management of Early Breast Cancer and the NZ Guidelines for Early Management of Breast Cancer that recommend patients who undergo BCS receive radiotherapy, 95% of all patients had postoperative radiotherapy after BCS. 8,9 This is well above the NBCA KPI that state that greater than 85% of invasive tumours treated with BCS should be referred for or prescribed radiotherapy.
Overall, 43% of patients had post mastectomy radiotherapy. The NBCA KPI also recommends radiotherapy for high risk mastectomy cases in which the tumour was larger than 50mm or there were 4 or more positive lymph nodes. The percentage of patients with high risk invasive cancer who received radiotherapy in the BSA group was significantly lower (p=0.047) than in the not BSA group.
The possible reasons why the NBCA KPI was not met in the high risk BSA patients are perhaps that these were older patients with more comorbidities, hormone receptor positive tumours and of lower grade.
Overall, 81% of New Zealand women with oestrogen positive invasive tumours had endocrine treatment. This figure is surprisingly low for receptor positive tumours. The possible explanations could be that the endocrine treatment may have been commenced after radiotherapy or by medical oncologists, and therefore not recorded in the database by the surgeon, or contraindications to therapy such as history of DVT or osteoporosis, or such low risk tumours that the clinicians/patient did not think that the side effects justified the benefits.
A small percentage of patients with oestrogen negative tumours were prescribed endocrine treatment. Presumably, these patients may have been progesterone receptor positive. Several studies have shown that there is some benefit of endocrine treatment in women who are oestrogen receptor negative but are progesterone receptor positive. However, it is clear that the benefit is less compared to women who are oestrogen receptor positive.10,11
A smaller proportion of patients in the BSA group had adjuvant chemotherapy reflecting the earlier stage, lower risk breast cancers being treated in the screen detected population. As expected, there was a higher proportion of patients receiving chemotherapy in the not BSA group, with a significant proportion of them being high risk as reflected by their negative hormone receptor status.
Overall, a high proportion of BSA patients met the standard guidelines and the NBCA KPI except for radiotherapy in high risk mastectomy cases. Most BSA surgeons need to be formally accredited by BSA to ensure patients receive high standard of care. The accreditation criteria include full participation in the RACS audit.
In general, New Zealand patients diagnosed with early invasive breast cancer were managed appropriately according to the New Zealand Guidelines for Early Management of Breast Cancer and the NBCA Key Performance Indicators. New Zealand surgeons should be congratulated with achieving a high level of participation in the NBCA audit.
Competing interests: None known.
Author information: Corinne W L Ooi, Breast and Endocrine Surgical Fellow, Department of Surgery, Waikato Hospital, Hamilton; Ian D Campbell, Clinical Director, Waikato Breast Care Centre, Hamilton; James Kollias, Senior Consultant Surgeon, Breast, Endocrine and Surgical Oncology Unit, Department of Surgery, Royal Adelaide Hospital, Adelaide, Australia; Primali de Silva, National Breast Cancer Audit, Australian Safety and Efficacy Register of New Interventional Procedures-Surgical (ASERNIP-S), Royal Australasian College of Surgeons, Adelaide, Australia
Acknowledgements: The paper is based on a report provided by the Royal Australasian College of Surgeons, National Breast Cancer Audit and the 2008 BreastScreen Aotearoa Data Report.
Correspondence: Corinne Wei Leng Ooi, 5 Chester Street, Bentleigh East 3165, Victoria, Australia. Fax: +61 (0)3 95755110; email: email@example.com
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