The appendix can harbour synchronous or metachronous tumours in patients with colorectal cancer (CRC)1, yet prophylactic appendicectomy is not routinely recommended. This study assessed the incidence of secondary appendiceal tumours after CRC surgery using Swiss population-based data.
The Swiss national cancer data set (National Agency for Cancer Registration) was analysed for the period 2009–20212. Adults with a first primary colorectal adenocarcinoma who underwent surgical resection in Switzerland were included. Patients with previous CRC, primary appendiceal cancer, or age < 18 years were excluded. Standardized incidence ratios (SIRs) compared the risk of second primary appendiceal tumours with that of the general Swiss population, adjusting for age, sex, and calendar year. Tumours diagnosed within 4 months of the CRC diagnosis were deemed synchronous; later diagnoses were considered metachronous3.
Among 25 714 patients who underwent CRC surgery (mean age 69 years, 44% female), 56 developed a second primary appendiceal tumour during 133 227 person-years of follow-up (incidence 42 per 100 000 person-years; Tables S1–S3). Most were neuroendocrine tumours (93%) and were detected within 4 months of CRC diagnosis (86%). Compared with the background Swiss population (incidence 1.83 per 100 000 person-years), the risk in this cohort was markedly increased (SIR 19.8; 95% confidence interval (c.i.) 15.0 to 25.4).
Sensitivity analyses confirmed elevated risk when limited to patients with metachronous tumours (8 patients; SIR 2.8, 95% c.i. 1.3 to 5.3) and when excluding patients who underwent right hemicolectomy (SIR 12.4; 95% c.i. 8 to 18.2). Excluding neuroendocrine tumours still yielded a slightly raised risk (SIR 3.2; 95% c.i. 1.0 to 7.4; Table 1).
Table 1.
Estimation of the risk for appendiceal tumours in patients operated on for CRC in Switzerland
| Observed no. of appendiceal tumours | Person-years at risk | Expected no. of appendiceal tumours | Age-standardized incidence ratio* | P | |
|---|---|---|---|---|---|
| Reference population | 1707 | 93 152 298 | 1 | ||
| All histologies | |||||
| Synchronous and metachronous | |||||
| Patients operated on for CRC | 56 | 133 227 | 2.83 | 19.76 (15.03, 25.40) | < 0.001 |
| Patients operated on for left-sided CRC | 23 | 85 827 | 1.86 | 12.38 (8.00, 18.15) | < 0.001 |
| Metachronous appendiceal tumours | |||||
| Metachronous | |||||
| Patients operated on for CRC | 8 | 133 466 | 2.84 | 2.82 (1.29, 5.25) | 0.003 |
| Patients operated on for left-sided CRC | 7 | 85 922 | 1.86 | 3.76 (1.62, 7.28) | < 0.001 |
| Non-NET tumours | |||||
| Synchronous and metachronous | |||||
| Patients operated on for CRC | 4 | 131 010 | 1.26 | 3.17 (0.98, 7.37) | 0.021 |
*Values in parentheses are 95% confidence intervals. CRC, colorectal cancer. NET, neuroendocrine tumours.
Overall, this nationwide analysis showed that patients undergoing CRC surgery have a nearly 20-fold higher incidence of appendiceal tumours than the Swiss population, and higher than described in other populations4,5. Most were early-stage neuroendocrine tumours of uncertain clinical significance. Although synchronous appendicectomy adds minimal operative risk in elective colorectal resections, the absolute benefit would be considered small, with prophylactic removal preventing appendiceal tumours in only 0.2% of the present cohort.
Limitations of this study include the lack of individual appendicectomy data and possible detection bias from intensified postoperative surveillance.
Supplementary Material
Acknowledgements
The authors thank the Cantonal Cancer Registries for collecting the data used in this study, namely Y. Bergeron (CR-FR), A. Bordoni (CR-TI), I. Curjuric and M. Adam (CR-AG), G. Defossez (CR-VD), J. Diebold (CR-LU/UR/OW/NW), S. Erny (CR-BS/BL), I. Konzelmann (CR-VS), M. Maspoli and J. L. Bulliard (CR-NE/JU), M. Mousavi (CR-SG/TG/AI/AR), A. Perren (CR-BE/SO), E. Rapiti (CR-GE), S. Rohrmann (CR-ZH/ZG/SH/SZ), and R. von Moos (CR-GR/GL). The authors also acknowledge the National Agency for Cancer Registration for merging the cantonal data and providing the national data, which enabled the national analysis.
Contributor Information
Jeremy Meyer, Division of Digestive Surgery, Department of Surgery, University Hospitals of Geneva, Geneva, Switzerland; Medical School, University of Geneva, Geneva, Switzerland.
Elin Meyer, Division of Digestive Surgery, Department of Surgery, University Hospitals of Geneva, Geneva, Switzerland; Medical School, University of Geneva, Geneva, Switzerland.
Evelyne Fournier, Medical School, University of Geneva, Geneva, Switzerland; Registre Genevois des Tumeurs, University of Geneva, Geneva, Switzerland.
Emilie Liot, Division of Digestive Surgery, Department of Surgery, University Hospitals of Geneva, Geneva, Switzerland; Medical School, University of Geneva, Geneva, Switzerland.
Guillaume Meurette, Division of Digestive Surgery, Department of Surgery, University Hospitals of Geneva, Geneva, Switzerland; Medical School, University of Geneva, Geneva, Switzerland.
Thibaud Koessler, Medical School, University of Geneva, Geneva, Switzerland; Department of Oncology, University Hospitals of Geneva, Geneva, Switzerland.
Christian Toso, Division of Digestive Surgery, Department of Surgery, University Hospitals of Geneva, Geneva, Switzerland; Medical School, University of Geneva, Geneva, Switzerland.
Justin Davies, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK; Colorectal Surgery Unit, University of Cambridge, Cambridge, UK.
James Wheeler, Addenbrooke’s Hospital, Cambridge University Hospitals NHS Foundation Trust, Cambridge, UK.
Katharina Staehelin, National Agency for Cancer Registration (NACR), Zürich, Switzerland.
Elisabetta Rapiti, Medical School, University of Geneva, Geneva, Switzerland; Registre Genevois des Tumeurs, University of Geneva, Geneva, Switzerland.
Frédéric Ris, Division of Digestive Surgery, Department of Surgery, University Hospitals of Geneva, Geneva, Switzerland; Medical School, University of Geneva, Geneva, Switzerland.
Lea Wildisen, National Agency for Cancer Registration (NACR), Zürich, Switzerland.
Funding
The authors have no funding to declare.
Author contributions
JM conceived and designed the study. LW acquired the data. JM, EM, EF, ER and LW analysed the data. All authors interpreted the data. JM, EM, EF, ER and LW contributed to the writing of the manuscript. All authors performed critical revision of the manuscript and approved its final version.
Disclosure
The authors declare no conflict of interest.
Supplementary material
Supplementary material is available at BJS Open online.
Data availability
Data are available upon reasonable request to the corresponding author.
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This section collects any data citations, data availability statements, or supplementary materials included in this article.
Supplementary Materials
Data Availability Statement
Data are available upon reasonable request to the corresponding author.