Background: Breast cancer is the most common cancer in Canadian women; nearly 25% of women diagnosed with cancer have breast cancer. The early detection of breast cancer is a major challenge because tumours often grow without causing symptom. The diagnosis of breast cancer at an early stage (stages I and II) improves survival outcomes because treatments are more effective and better tolerated. To better inform the prevention of and screening for breast cancer, simulations using modifiable rather than non-modifiable risk factors may be helpful in shifting the stage at diagnosis downward. Methods: Breast cancer stages were simulated using the data distributions from Alberta’s Tomorrow Project participants who developed breast cancer. Using multivariable partial proportional odds regression models, modifiable lifestyle factors associated with the stage of cancer at diagnosis were evaluated. The proportions or mean levels of these lifestyle factors in the simulated population were systematically changed, then multiplied by their corresponding estimated odds ratios from the real data example. The effects of these changes were evaluated singly as well as cumulatively. Results: Increasing total dietary protein (g/day) intake was the single most important lifestyle factor in shifting the breast cancer stage downwards followed by decreasing total dietary energy intake (kcal/day). Increasing the proportion of women who spend time in the sun between 11 am and 4 pm in the summer months, who have had a mammogram, who have been pregnant or reducing the proportion who are in stressful situations had much smaller effects. The percentage of Stage I diagnoses could be increased by approximately 12% with small modifications of these lifestyle factors. Conclusion: Shifting the breast cancer stage at diagnosis of a population may be achieved through changes to lifestyle factors. This proof of principle study that evaluated multiple factors associated with the stage at diagnosis in a population can be expanded to other cancers as well, providing opportunities for cancer prevention programs to target specific factors and identify populations at higher risk.
背景：乳腺癌是加拿大女性中最常见的癌症；近25%被诊断患有癌症的女性为乳腺癌患者。乳腺癌的早期检测是一项重大挑战，因为肿瘤常在无症状情况下生长。早期（I期和II期）诊断乳腺癌可改善生存结局，因为此时治疗效果更佳且耐受性更好。为更好地指导乳腺癌的预防与筛查，利用可改变而非不可改变的风险因素进行模拟，可能有助于推动诊断阶段前移。 方法：利用阿尔伯塔未来计划项目中乳腺癌参与者的数据分布模拟乳腺癌分期。通过多变量部分比例优势回归模型，评估与诊断时癌症分期相关的可改变生活方式因素。系统调整模拟人群中这些生活方式因素的比例或平均水平，再乘以真实数据示例中对应的估计优势比。分别评估单一因素变化及多因素累积变化的影响。 结果：增加膳食总蛋白质摄入量（克/天）是推动乳腺癌诊断阶段前移最重要的单一生活方式因素，其次是减少膳食总能量摄入（千卡/天）。提高夏季上午11点至下午4点间晒太阳的女性比例、接受过乳腺X光检查的女性比例、有过妊娠经历的女性比例，或降低处于高压情境的女性比例，产生的效果则小得多。通过对这些生活方式因素进行小幅调整，I期诊断比例可提升约12%。 结论：通过改变生活方式因素，可能实现人群乳腺癌诊断阶段的前移。这项评估多因素与人群诊断分期关联的原理验证研究，可扩展至其他癌症类型，为癌症预防项目提供靶向特定因素、识别高风险人群的机遇。
Stage Shifting by Modifying the Determinants of Breast Cancer Stage at Diagnosis: A Simulation Study
肿瘤(癌症)患者之家