Cohort Definition Name: Primary adenocarcinoma of rectum MSI-L, MSI-indeterminate, MSS or pMMR, oncological treatment, no surgery
Contributor name: Andreas Weinberger Rosen
Contributor OrcId: 0000-0001-9990-8155
Logic Description: First event of oncology in patients diagnosed with primary adenocarcinoma of rectum with MSI-L, MSI-indeterminate, MSS or pMMR profile, with no subsequent potentially curative surgery
Recommended study application: exposure.
Assertion statement: This cohort definition was executed on at least one real person-level observational health data source and resulted in a cohort with at least 1 person.
Submitted cohort definition:
Target Clinical Description
Rectal cancer, a primary adenocarcinoma of the rectum, accounts for around one-third of colorectal cancer. The disease originates in the epithelial cells lining the rectal wall and through several molecular pathways evolves into a malignant tumor. Clinical presentation varies based on the tumor’s anatomical location within the rectum, its size, and stage at diagnosis.
Presentation of Rectal Cancer
- Hematochezia or blood in the stool
- Altered bowel habits, notably urgency or frequency
- Tenesmus or the persistent feeling of the need for bowel evacuation
- Lower abdominal or rectal pain
- Unexplained weight loss
- General fatigue
Some patients may be asymptomatic and could be identified via screening procedures or during other unrelated medical assessments.
Severe cases of rectal cancer may necessitate emergency intervention due to complications like bowel obstruction, acute lower gastrointestinal bleeding, or rectal perforation.
Assessment for Rectal Cancer
- Colonoscopy, proctoscopy or sigmoidoscopy for initial examination and biopsy collection
- Histopathological analysis of biopsy tissue for definitive diagnosis
- Advanced imaging modalities such as pelvic MRI, CT, or PET for clinical staging
- Histological evaluation of resected or metastatic tissue samples for pathological staging
Differential Diagnosis of Rectal Cancer
- Other rectal neoplasms such as neuroendocrine tumors or GIST (Gastrointestinal Stromal Tumors)
- Anal neoplasias
- Diverticulitis affecting the lower colon
- Hemorrhoids or anal fissures
- Proctitis or rectal inflammation
- Irritable Bowel Syndrome (IBS)
- Inflammatory Bowel Disease (IBD), specifically Crohn’s disease or ulcerative colitis
Treatment Plan for Rectal Cancer
- For localized or regional confined cases, surgical resection of the rectum or local resections is potentially curative
- The surgical intervention might be combined with adjuvant or neoadjuvant therapy, including antineoplastic drugs or radiotherapy
- For solitary metastasis curative treatment might be possible with the combination of surgical resection of the primary tumor and metastasectomy, radiofrequency ablation, or stereotactic radiation of the metastasis together with other oncological treatment
- Palliative oncological therapy and surgical might improve survival and quality of life for patients where there is no curative treatment option.
- Patients with tumors with a deficient mismatch repair or microsatellite instability-high molecular profile might be candidates for immune checkpoint inhibitor treatment.
Prognosis for Rectal Cancer
The prognosis depends on several factors such as the stage of the disease at diagnosis and the possibility to offer curative treatment, along with other comorbidities. A diagnosis at an early stage followed by curative surgery usually indicates a more favorable prognosis, while late-stage or emergency presentations are generally associated with poorer outcomes.
Patients with tumors with the MSS/MSI-L/pMMR molecular profile generally have a worse prognosis compared with patients with tumors of the MSI-H/dMMR subtype.
Assignment for Peer Review:
Peer review of the phenotype would be more than welcome