This multicentre randomized controlled trial aims to investigate whether an individualized comprehensive geriatric assessment (CGA) and care will improve postoperative results in frail elderly patients undergoing surgery for colorectal cancer. The study will take place in departments applying the ERAS-concept which is considered gold standard in colorectal surgery.

Colorectal cancer is the third most common cancer form in Sweden with an incidence of approximately 6000 new cases annually. It affects mainly elderly people; 65 % of patients diagnosed with colon- or rectal cancer are older than 65 years, and more than half are 70 years of age or older when diagnosed. Surgery is the treatment of choice for colon and rectal cancer if cure is to be achieved, sometimes in combination with radio- and/or chemotherapy. With increasing age many patients acquire other medical conditions which in turn can affect the patient's general status and thus impair their chances to recover from cancer treatment.

Age is a well-known risk factor for post-operative complications. Furthermore, it has been established that assessing frailty in elderly patients is a more precise way of detecting patients with increased vulnerability. In recent years increasing research has focused on frailty in regards of different medical conditions and treatments. A large amount of studies has also been conducted on the concept of frailty and surgery, and there is solid knowledge of the impact of frailty on outcome after surgery. It is also known that elderly frail patients suffers a higher risk of severe post-operative complications and morbidity compared to elderly non frail patients in the terms of elective surgery for colon- and rectal cancer.

Several different tools for determining and measuring frailty has been developed and studied. A commonly used definition is the accumulation of deficits model, which adds together a person's different diseases and disabilities. A widely used instrument based on this concept is the Canadian Study of Health and Aging (CSHA) Clinical Frailty Scale (CFS-9). It utilises a 9-point instrument to assess frailty. A score of 5 or more defines frailty, and the higher the score the more severe the degree of frailty. The instrument has been extensively studied and validated and is highly correlated to the degree of frailty as measured with much more extensive frailty tools. The instrument is easy to use and not very time-consuming which makes it practical to use in everyday clinical practice; therefore rendering it relevant to use in clinical studies.

As stated, there are evidence that the group of frail elderly patients have inferior results after colorectal surgery, compared to elderly non-frail patients. Comprehensive geriatric assessment (CGA) and care is a well-established and effective way of providing health care. It has been proven to be beneficial in terms of outcome after hospitalization for the group of frail elderly in various other settings. A multicentre randomized controlled trial conducted in Norway evaluated preoperative geriatric assessment prior to surgery for colorectal cancer in frail patients ≥ 65 years of age. The patients in the intervention group were assessed by a medical doctor specializing in geriatric medicine who gave individual advice regarding medical changes, exercise, nutrition etc. The median time of intervention before surgery was six days. The study could not show any significant differences in post-operative complications. Except having a brief time span for the intervention, the study was smaller than the initial estimation, with a total of 116 included patients. Another randomized controlled study has been conducted regarding prehabilitation prior to surgery for colorectal cancer in frail patients, analysing 30-day complications. The prehabilitation in this study consisted of exercise, nutritional and psychological interventions four weeks prior to surgery, and could not establish any differences in 30-day complications rates compared to a group that received rehabilitation four weeks after surgery. Further, there is an ongoing randomized controlled international study aiming to evaluate the impact of multimodal prehabilitation - in terms of exercise, nutritional and psychological interventions prior to colorectal surgery in adults, not specifically frail patients. There is also an ongoing randomized controlled study - the GERICO study - on frail elderly patients receiving chemotherapy for colorectal cancer with the aim to see if geriatric intervention affects outcome.

Intervention studies using CGA and care as an intervention to improve outcome for frail elderly patients has been conducted in terms om hip fracture and abdominal surgery, so far with mixed results. A systematic review of these studies from 2017 concluded that there is a need of a larger randomized multicentre study to evaluate the possible advantage of such an intervention for frail elderly patients prior to surgery.

Inclusion Criteria:

• Potentially curable colorectal cancer (according to cTNM)
• ≥ 70 years old
• Frailty (CFS-9 v2.0 score 4-8)

Exclusion Criteria:

• Palliative situation
• Unable to understand study information
• Acute surgery
• Terminally ill patient (CFS-9 9)
• Less than 6 months expected survival
• Not willing to participate

It will not be possible to mask for either patients nor participating health care professionals if patients are enrolled in the control- or intervention group. Hence, the study will not be blinded. When the final data analysis is performed the person performing the analysis will not be aware of which group each patient was a part of.