The early detection of colorectal cancer (CRC) through regular screening decreases its incidence and mortality rates and improves survival rates. Norway has an extremely high percentage of CRC cases diagnosed at late stages, with large variations across municipalities and hospital catchment areas. This study examined whether the availability of physicians related to CRC primary diagnosis and preoperative investigations, or physician density, contributes to the observed geographical differences in late-stage incidence rates. Municipality-level data on CRC stage at diagnosis were obtained from the Cancer Registry of Norway for the period 2012–2020. Physician density was calculated as the number of physicians related to CRC investigations, general practitioners (GPs) and specialists per 10,000 people, using physician counts per municipality and hospital areas from Statistics Norway. The relationship was examined using a novel causal inference method for spatial data—neighbourhood adjustment method via spatial smoothing (NA approach)—which allowed for studying the region-level effect of physician supply on CRC outcome by using spatially referenced data and still providing causal relationships. According to the NA approach, an increase in one general practitioner per 10,000 people will result in a 3.6% (CI −0.064 to −0.008) decrease in late-stage CRC rates. For specialists, there was no evidence of a significant correlation with late-stage CRC distribution, while for both groups, GPs and specialists combined, an increase of 1 physician per 10,000 people would be equal to an average decrease in late-stage incidence rates by 2.79% (CI −0.055 to −0.001). The study confirmed previous findings that an increase in GP supply will significantly improve CRC outcomes. In contrast to previous research, this study identified the importance of accessibility to both groups of physicians—GPs and specialists. If GPs encounter insufficient workforces in hospitals and long delays in colonoscopy scheduling, they will less often recommend colonoscopy examinations to patients. This study also highlighted the efficiency of the novel methodology for spatially referenced data, which allowed us to study the effect of physician density on cancer outcomes within a causal inference framework.

中文翻译：

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医生密度对结直肠癌诊断分期的影响：应用于区域级数据的空间数据因果推理方法

通过定期筛查早期发现结直肠癌 (CRC) 可降低其发病率和死亡率并提高生存率。挪威在晚期诊断出的 CRC 病例中所占比例极高，各城市和医院服务区之间的差异很大。本研究检查了与 CRC 初步诊断和术前调查相关的医生的可用性或医生密度是否有助于观察到的晚期发病率的地理差异。从挪威癌症登记处获得 2012-2020 年期间诊断时 CRC 分期的市级数据。医生密度计算为每 10,000 人中与 CRC 调查相关的医生、全科医生 (GP) 和专家的数量，使用来自挪威统计局的每个城市和医院区域的医生计数。使用一种新的空间数据因果推理方法——通过空间平滑（NA 方法）的邻域调整方法——检查这种关系，该方法允许通过使用空间参考数据并仍然提供因果关系来研究医生供应对 CRC 结果的区域级影响. 根据 NA 方法，每 10,000 人增加一名全科医生将导致晚期 CRC 率降低 3.6%（CI -0.064 至 -0.008）。对于专科医生，没有证据表明与晚期 CRC 分布有显着相关性，而对于两组、全科医生和专科医生加起来，每 10,000 人增加 1 名医生将等于晚期发病率平均下降2.79% (CI -0.055 至 -0。001). 该研究证实了先前的发现，即增加 GP 供应将显着改善 CRC 结果。与之前的研究相比，这项研究确定了两组医生（全科医生和专科医生）可及性的重要性。如果全科医生遇到医院人手不足和结肠镜检查排程长期延误的情况，他们就不会经常向患者推荐结肠镜检查。这项研究还强调了空间参考数据的新方法的效率，这使我们能够在因果推理框架内研究医生密度对癌症结果的影响。这项研究确定了两组医生（全科医生和专科医生）可及性的重要性。如果全科医生遇到医院人手不足和结肠镜检查排程长期延误的情况，他们就不会经常向患者推荐结肠镜检查。这项研究还强调了空间参考数据的新方法的效率，这使我们能够在因果推理框架内研究医生密度对癌症结果的影响。这项研究确定了两组医生（全科医生和专科医生）可及性的重要性。如果全科医生遇到医院人手不足和结肠镜检查排程长期延误的情况，他们就不会经常向患者推荐结肠镜检查。这项研究还强调了空间参考数据的新方法的效率，这使我们能够在因果推理框架内研究医生密度对癌症结果的影响。