The Hong Kong Breast Cancer Registry (HKBCR), run by the Hong Kong Breast Cancer Foundation (HKBCF), launched its 16th annual research report today. The report aimed to shed light on the comparison between the patients of de novo metastatic breast cancer (dnMBC) (stage IV) and early breast cancer (eBC) (stages I-II). The findings revealed that nearly 80% of dnMBC patients had never undergone regular breast screenings, and 42.2% had never had any breast screenings. Additionally, many delayed for more than three months to seek medical consultation after noticing symptoms.

The report also adopted a new prognostic staging system for patients with dnMBC proposed by Plichta team in the United States to predict patient survival, aiding in the design of personalized treatment strategies. Dr. Polly CHEUNG, Founder of the HKBCF and Co-Chairman of the HKBCR Steering Committee, said, "The number of stage IV breast cancer cases in Hong Kong continues to rise, with a five-year overall survival rate of approximately 55%, significantly lower than that of the entire breast cancer cohort (about 95%).^[1] Doctors can use the staging system to more accurately analyze the risks and survival rates of stage IV breast cancer patients, allowing for personalized management that improves survival and gives hope." Dr. Cheung also emphasized that the report results confirm the need to raise breast health awareness among women in Hong Kong.

dnMBC, defined as the presence of distant metastases at the time of initial diagnosis, is a distinct clinical entity that is not uncommon in Hong Kong. According to the 8th edition of the American Joint Committee on Cancer (AJCC) staging for breast cancer, any metastatic status would automatically equate to a stage IV disease.^[2] In 2021, 9.3% of 5,565 new invasive breast cancer cases in Hong Kong were stage IV.^[3]

The HKBCR Report No. 16 analyzed data from women who were diagnosed with invasive breast cancer between 2006 and 2018, and recruited in the HKBCR. A group of 430 dnMBC and 1,711 eBC (stages I-II) patients with self-detection have been compared in terms of the baseline demographics, socioeconomic factors, and breast screening habits etc.

Had three or more risk factors

Dr. Carol Kwok, Member of the HKBCR Steering Committee, highlighted that around 70% of them had three or more risk factors known to be associated with the development of breast cancer, such as no or late childbirth, no breastfeeding, as well as other modifiable lifestyle risk factors like obesity and lack of exercise. There was no statistically significant difference between the two groups with reference to the age, baseline body mass index (BMI), personal history of benign breast disease, baseline demographics, socioeconomic background, education level, occupation, and monthly household income.

Never had any previous or regular screening

Nearly 80% of dnMBC patients had never undergone regular breast screenings, and 42.2% had never had any breast screenings. 50% of them had never performed breast self-examination. In addition, more patients of dnMBC presented a delay of more than three months from symptom onset. At diagnosis, more dnMBC patients had two or more symptoms and presented symptoms beyond a painless breast lump, such as nipple retraction and ulceration. These results may reflect poor breast health awareness of dnMBC patients.

Staging system better estimates survival

When reviewing the clinical and survival data for the 463 dnMBC patients diagnosed in the study period, over 80% of patients were aged 40-69 years at presentation, with a median age of 54. With a median follow-up period of 50 months, the median overall survival (OS) for the entire cohort was 63 months, and the 5-year OS was 51.8%. When categorised by tumour biological subtypes, 55.7% of the tumours were luminal [i.e. hormone receptor (HR)-positive HER2-negative], 21.4% were HR+ HER2+, 13.9% were HR- HER2+ and 9.4% were triple-negative breast cancer. No statistically significant differences in survival distributions were found between different subtypes.

When applying the novel prognostic staging system proposed by Plichta team,^[4] which classified the patients with similar 3-year OS into stages IV A-D based on factors such as tumour characteristics, receptor status, number and sites of metastases etc, 258 dnMBC patients could be grouped. Among them, 5.4% of the patients were stage IVA, 47.7% stage IVB, 35.7% stage IVC and 11.2% stage IVD. Table 1 depicts the Kaplan-Meier estimates of OS stratified by the assigned stage IV A-D. Patients at stage IVD had poorer survival than those at stages IVA and IVB (p<0.008).

Table 1. Kaplan-Meier estimates of OS by assigned stage group (N=258)

The survival results may suggest that other factors, such as sites and extent of metastases, would provide prognostic information beyond subtypes, and hence show the need to further categorise stage IV disease. If the novel prognostic staging system could be validated, it would be useful to design personalized management strategies. However, further research is warranted to elucidate the underlying biological differences between the different subgroups of dnMBC, and to develop more effective therapeutic strategies for this disease entity.

Dr. Eliza Fok, Chairman of the HKBCF said, "The reasons for never or irregular breast screenings include busy lifestyles, a personal belief that the risk is low, laziness, and concerns about screening costs. The longer delay in seeking medical consultation among those diagnosed with dnMBC after symptoms appear, along with poor screening habits, reflects the need to further enhance breast health awareness among women in Hong Kong. Women aged 40 or above should remember to perform breast self-examination monthly and undergo clinical check-ups and mammograms every two years. The District Health Centre should strengthen efforts to promote regular breast screenings for women."

Dr. Eliza Fok noted that Taiwan (China), South Korea, and the United States have all implemented universal breast cancer screening programs. Therefore, she recommended that the HKSAR government roll out a three-phase plan for universal breast cancer screening, starting with high-risk women, followed by women in low-income areas, and finally, based on the experiences from these two phases, implement universal screening for all.