The main findings in this study show a rising breast cancer incidence in both Crete and Sweden, however, a paradox is that mortality rate in Crete has increased last decade, while in Sweden, breast cancer mortality decreased. This is a striking difference in the pattern of breast cancer burden for populations of these two regions on the European continent. Regarding survival rates, trends of survival in Sweden have increased over time in contrast to a lack of improvement - and even small decline - in survival on Crete since 1995.
The findings in this study must be seen against a multifactorial background where both health care systems as well as life-style factors and salutogenic factors might play important roles. Breast cancer mortality and survival are tightly related. It is generally stated, that one of the most important, modifiable, known parameters with influence on prognosis is early detection as a prerequisite for early, effective treatment with medical drugs and interventions that is already known to work [18].
In many European countries like the Scandinavian countries, Germany, Italy, Spain, Poland and others, there has been a marked reduction in the breast cancer mortality rates (between 8 and 19%) for the last years. This reduction has in general been attributed to earlier detection and improved treatment [11]. However, in Greece, a national mammography screening program has yet to be fully implemented [20]. There is yet no nationally formulated strategy for early detection of breast cancer in Greece.
Several factors are involved in the process leading to diagnosis, from the individuals own detection and insight at the debut of symptoms, to the availability and utilization of local health care. Mammographic screening on a population level is an established method to approach early detection of breastcancer before clinical symptoms occur [25]. In Sweden, 60% of all breast cancer cases are detected through the national screening program for women between 40 and 74 years of age [21, 26]. In countries with a tradition of mammography screening of breast cancer, an increase in incidence rates and a decrease in mortality rates have been evident for decades [27]. This may point to an increased incidence related to improved diagnostics but may also stem from risk of overdiagnostic. Nevertheless, potential overdiagnostic may complicate the interpretation of epidemiological health statistics. In a metaanalysis from 2012, the overdiagnostics was estimated to be 11% during lifetime for a woman invited to the screening program, and 19% during the specific time-period of inclusion in the screening program [28]. However, in many countries the incidence rise began before the mammography screening programs were implemented, also seen in countries who introduced screening programs relatively late [27]. In different populational settings, different challenges are distinguished related to features of the population [29]. The mammography screening of women, at least for the age-group 50-69 years, is one way to significantly reduce mortality rates of breast cancer [25], but mammography screening is also under an ongoing debate [30].
Another way into early diagnosis, is to make the diagnostical process per se more effective. In Sweden, a time-regulated, standardized, health care process is used when symptoms leading to high suspicion of breast cancer. Through this process, from the referral of the patient to a specialized oncological hospital unit, the individual has priority to required examinations and the time space between examinations and clinical consultations are strictly time-regulated [19].
The structure of the health care systems and the availability of health care differ between the studied regions, but there are also similarities, as illustrated in Table 1. In a time perspective, the Greek economy experienced a long period of recession during the period 2007-2015, with retrenchments in health care [31]. After the Greek recession, factors like quality of treatment as well as funding and access to health care have been stated a particular challenge of the society [32]. Interestingly, these years of economic recession overlaps the period of declination of the 10-year survival in Greece.
Sociocultural aspects with discrepancies in perceptions of health and disease may be factors of concern regarding general health literacy among the populations studied [17, 33]. In a study of Cretan women, several reasons for not using mammography were identified, like poor knowledge of the benefits of mammography screening, lack of physician recommendation, costs, embarrassment, fear of pain during the procedure and fear of a serious diagnosis [33]. Sociocultural aspects regarding doctor-patient relations and areas associated with high personal integrity, like the clinical investigations of the female breast, might play a role in patient-compliance. Communicative factors, such as language barriers, might also be factors of concern.
The strength of the study is that both the Swedish and Cretan data derives from solid and reliable registers. In Sweden, there is a historical tradition of registries with one of the world’s oldest cancer registries, started in 1958, with a national coverage [21]. The reporting of all new cancer cases is obligatory by law in Sweden, both from physician in charge as well as the responsible unit for pathological and cytological laboratory. In this way, the Swedish Cancer registry cover approximately around 99% of all cases and in 2015 an investigation showed that 100% of the reported cases were verified with cytology or histology, pointing to a valid and accurate measure [24]. National cancer registry is not yet available for the whole country of Greece, but for the region of Crete. The Cancer Registry of Crete has reached high numbers of data quality by following the European Network of Cancer Registries (ENCR) quality standards, which evaluate four dimensions (i.e., completeness, reliability, timeliness, and continuity). A limitation in this study is that the Greek data is only available from a specific region of the country, the island of Crete. The Swedish screening tool might introduce some bias. According to Swedish National Quality Registry of Breast Cancer (NKBC), every tumor of the breast found through screening is treated even if the knowledge is scarce about how the tumor would have developed with time if left untreated [27]. This perception may have influence on the incidence as well as the mortality data, possibly contributing to higher number of cases found, and consequently lower mortality rate in Sweden.
In conclusion, this study shows a contrasting pattern of breast cancer burden between two corners of the same European continent. Although the incidence is slowly rising in both regions, the mortality is increasing on Crete in contrast to Sweden where the mortality trend is decreasing. The findings further reveal a rising survival rate in Swedish breast cancer patients, while the survival trends on Crete are falling. An interpretation of these findings is that differences in health care systems and health policies as well as sociocultural factors between the two countries might play an important role on the outcome of breast cancer. The findings also indicate the need for a national breast cancer strategy in Greece, possibly with a national screening program and a streamlined, standardized course of investigation to improve early diagnostical processes and early treatment.
