Volume-outcome relationship for colorectal cancer in primary care: a prospective cohort study

Purpose Higher caseloads are associated with better outcomes for many conditions treated in secondary and tertiary care settings, including colorectal cancer (CRC). There is little known whether such volume-outcome relationship exist in primary care settings. The purpose of this paper is to examine general practitioner (GP) CRC-specific caseload for possible associations with referral pathways, disease stage and CRC patients' overall survival. Design/methodology/approach The paper retrospectively analyses a prospectively maintained CRC database for 2009-2014 in a single district hospital providing bowel cancer screening and tertiary rectal cancer services. Findings Of 1,145 CRC patients, 937 (81.8 per cent) were diagnosed as symptomatic cancers. In total, 210 GPs from 44 practices were stratified according to their CRC caseload over the study period into low volume (LV, 1-4); medium volume (MV, 5-7); and high volume (HV, 8-21 cases). Emergency presentation (LV: 49/287 (17.1 per cent); MV: 75/264 (28.4 per cent); HV: 105/386 (27.2 per cent); p=0.007) and advanced disease at presentation (LV: 84/287 (29.3 per cent); MV: 94/264 (35.6 per cent); HV: 144/386 (37.3 per cent); p=0.034) was more common amongst HV GPs. Three-year mortality risk was significantly higher for HV GPs (MV: (hazard ratio) HR 1.185 (confidence interval=0.897-1.566), p=0.231, and HV: HR 1.366 (CI=1.061-1.759), p=0.016), but adjustment for emergency presentation and advanced disease largely accounted for this difference. There was some evidence that HV GPs used elective cancer pathways less frequently (LV: 166/287 (57.8 per cent); MV: 130/264 (49.2 per cent); HV: 182/386 (47.2 per cent); p=0.007) and more selectively (CRC/referrals: LV: 166/2,743 (6.1 per cent); MV: 130/2,321 (5.6 per cent); HV: 182/2,508 (7.3 per cent); p=0.048). Originality/value Higher GP CRC caseload in primary care may be associated with advanced disease and poorer survival; more work is required to determine the reasons and to develop targeted intervention at local level to improve elective referral rates.