Breast cancer (X76)

March 3, 2023

Clinical course of breast cancer

Signs and symptoms of breast cancer may include a lump in the breast or eczema at the nipple. In symptomatic women, mammography or breast ultrasound can indicate breast cancer. Breast cancer may also be detected by mammography screening without symptoms. 

The diagnosis is made when malignant epithelial cells are found. The most common histologic types are infiltrating ductal, infiltrating lobular and mixed ductal/lobular carcinomas. 

To detect breast cancer in an early stage, all Dutch women aged between 50 to 75 years receive an invitation to participate in screening with mammography every 2 years. 

Factors that are associated with an increased risk of breast cancer include increasing age, female sex, a family history of breast cancer, drinking alcohol, smoking, and having oestrogen and progesterone circulating for a long time. Examples of long hormonal exposure are early menarche (first menstrual period at a young age), late menopause, nulligravidity (having never been pregnant), giving first birth at an older age and using postmenopausal hormone therapy. Breastfeeding and physical activity reduce the risk of breast cancer. 

Most women (around 98%) will survive breast cancer for 5 years or more after diagnosis. Treatment occurs in secondary or tertiary care and depends on the stage of breast cancer at presentation. Specialist treatment may involve surgery, radiation therapy and medical oncology (e.g. chemotherapy, hormonal treatment, immunotherapy). 

In the text below, we will only focus on female breast cancer.

How is breast cancer recorded in FaMe-Net?

Breast cancer is coded in ICPC-2 with X76. 

Epidemiology of breast cancer in FaMe-Net

Incidence of breast cancer is 1.5 per 1000 patient years, meaning 1.5 new diagnoses per 1000 female patients per year. The diagnosis is generally made after 45 years of age with also some cases in the age group 25-44. Incidence is highest in patients aged 65-74 and 75+ years (4.0 per 1000 patient years). Link/Figure 1

Prevalence of breast cancer is 12.8 per 1000 female patient years. This means that among 1000 female patients per year 13 have (had) breast cancer and sought help from the GP for it. Prevalence is highest in patients aged 65-74 years: 47.5 per 1000 patient years. Link/Figure 2

The higher number of prevalence compared to incidence indicates that breast cancer may behave as a chronic disease, requiring ongoing GP attention after the diagnosis. 

How do patients with breast cancer present to their GP?

The most common reason for encounter (RFE) for breast cancer is a breast lump/mass, presented in one third of all new diagnoses breast cancer. Another frequent reason for starting this episode is an abnormal screening result. Link/Table 3 The GP can receive this result as a letter (RFE *62), the screening care provider can contact the GP about the abnormal finding (*65) or the GP can initiate the contact with the patient in response to an abnormal screening result (*64). In the younger women with breast cancer (25-45 years), a breast lump/mass is even more common as initial RFE of the episode breast cancer, but note that these numbers are low. Link/Table 4 

In previous research with FaMe-Net data, a positive predictive value of 15% was found for diagnosing breast cancer in patients aged 45 years and older with a breast lump. This means that 15% of these patients presenting with a breast lump will be diagnosed with breast cancer. The current positive predictive value is 10%. Link/Table 5 The lower percentage is probably caused by the younger average age of women contributing to the most recent data as compared to the previously published data: after new practices joined the registration in 2014, the age composition of the entire FaMe-Net population shifted towards a smaller proportion of older patients, resulting in a lower average age in the group over 45 years. 

How do FaMe-Net GPs act

When the diagnosis is still unclear, GPs perform diagnostic radiology / imaging or refer to a specialist, most often a surgeon. During a breast cancer episode, the most common intervention by GPs is prescription of medication. Link/Table 6; Link/Table 7

Most commonly, anti-oestrogens and aromatase inhibitors are prescribed. Link/Table 8 

Referral to physical therapy is also a common intervention. Link/Table 9

Reference list:

Van Boven et al. The diagnostic value of the patient’s reason for encounter in diagnosing cancer in primary care.  JABFM 2017. 

(FaMe-Net list of publications)

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