The results of this study showed that the patients' survival rate who had received both surgery and chemotherapy was higher than the patients with no treatment or only one type of treatment. Univariate regression analysis showed a lower HR in patients who had received surgery and radiotherapy, but multivariate regression analysis did not show any significant difference in this group. The median survival time for the patients who had not received any kind of treatments was lower compared to other patients.
The one, three and five-year survival rate were %87, %57 and %33 respectively and the median survival time was 42.6 months. In a systematic review study by Hoseini et al, (34) on the survival rate of the colorectal cancer patients, the results showed that 1, 3 and 5-year survival times were %85.9, %64.9 and %52.5 respectively and the survival median time was 52.2 months.
The type of treatment received and its effects on the survival rate of CRC patients have been investigated in other studies. Mehrabani et al, (35) found no significant relationship between the kind of received treatment by the patients (surgery, chemotherapy, radiotherapy, combination of them) and their survival times, but the mortality rate was higher in patients with no treatment (HR = 11.3, %95 CI 2.37–54.7).
Moreover, a study done by Asghari in Iran (36) showed that the mortality rate in patients who had received radiotherapy, chemotherapy and immunotherapy was 2.3 times more than the patients whose initial treatment had been surgery, which can be due to the tumor cells' characteristics. Lohavinij in Thailand (1) showed that chemotherapy after surgery indicates a good prognosis for CRC patients. Furthermore, Folkesson (37), in a study in Sweden, showed that patients' survival rate who had received both surgery and radiotherapy was higher compared to those who had only received surgery. Another study in Iran, also, showed that those patients who had received chemotherapy after surgery had a lower mortality rate (P = 0.018) (38).
Moreover, Simmonds et al, in a meta-analysis clinical trial study on the effects of chemotherapy on the patients' survival rate in advanced stages, showed that the death risk has significantly decreased in patients who had received chemotherapy (HR = 0.65, %95 CI 0.56–0.76 ). The survival median time was 8 months in the control group and 11.7 month for the trial group (11). In another meta-analysis clinical trial study by Buyes et al, it was shown that patients' survival rate who had received Fluoropyrimidines as an initial chemotherapy medicine was higher than those patients received Bolus Fluoropyrimidines (OR = 0.48, %95 CI 0.40–0.57) (39). Surgery is known to be the main and basic treatment for patients with CRC, and patients with emergency surgery seem to have a higher mortality rates compared to those with an elective surgery (40, 41). In a meta-analysis study, the results showed that a good follow up after surgery is influential on the patients’ mortality rates (OR = 0.81, %95 CI 0.70–0.94) (42). Nevertheless, using other types of treatment including chemotherapy and radiotherapy can help decrease the disease relapse(43). Therefore, using chemotherapy or radiotherapy with surgery, in order to improve the patients' survival rate, is increasing nowadays. Radiotherapy is, recently, used with or without chemotherapy to kill the remaining cancerous cells after surgery or to decrease the tumor volume in order to facilitate the tumor surgery procedure. The standard treatment method is different for various patients based on the tumor size and location and the patients' physical condition, and choosing the right kind of treatment by the physicians can enhance the likelihood of the treatment success.
One of the reasons for less survival rate in patients who only received chemotherapy or surgery in Kurdistan province can be that they were not able to pay for the high cost of chemotherapy and surgery. Moreover, Low economic status, low income because of low jobs and no supplementary insurance to cover all costs can be other reasons in this regard (44, 45). At the same time, patients who received both chemotherapy and surgery seem to have a better economic situation; therefore, they were able to go to private hospitals in larger cities with better treatment facilities that meet higher health standards.
The tumor diagnosis in those patients' who received combined treatment of radiotherapy, chemotherapy and surgery might have occurred in advanced stages and they might have had worse health conditions in that time. Although the time interval between chemotherapy and radiotherapy and surgery is a controversial issue, the common interval time from the last session of chemotherapy to surgery is about 4–6 weeks. There are contradictory results about the amount of interval time between radiotherapy and chemotherapy and surgery in various observational studies. The difference in survival rate might be between the patients received a combination of chemotherapy and surgery and those received only surgery, chemotherapy or radiotherapy which requires further investigation (46–49).
The increase of CRC incidence in older people can affect the survival rate of the patients too, so as the risk of death during 30 days after surgery has considerably increased in older patients. In a study in Netherlands, the mortality rate after surgery in 90–99 year-old patients had increased in comparison to 80–89 year-old ones, so as the mortality rate had increased %8 in 80–84 year-old, %13 in 85–90 year-old patients and %20 in patients more than 90 years old (50).
The results of this study, from the view point of age increase and the decrease in the survival rate is in line with other studies, however; worse prognosis in young patients have been reported in some other studies. The reason for this difference can be due to the type of treatment received by the patients and diagnosis of the cancer in advanced stages (51–53).
In older patients there might be some other diseases along with their cancer which make their physical condition worse and it prevents them to receive surgery (50). The survival rate in older patients with comorbidity was half compared to other patients based on Charlson Co-morbidity Index (54). In some other studies, the results showed that CRC in young people is more invasive, diagnosed in later and advanced stages and it has worse pathologic results and lower survival rate as well (13, 55–57). Yet, selection bias in choosing the proper and right treatments of surgery and/or chemotherapy in older patients and those with underlying diseases should not be neglected. The kind of hospital (public or private), treatment facilities, surgery and the surgeons' experience and skill might affect the survival rate of the patients too.
Better economic status is known to be influential on the patients' survival rate. Uni- and multivariate Cox regression analysis showed that patients with better economic status had higher survival times (HR = 0.47, %95 CI 0.29–0.78, P = 0.022). Some other studies have shown that economic status was an important and determinant factor in increasing the patients' survival rate (56). The results of those studies showed that the patients with a lower economic status had less access to medical facilities and their mortality rate was 1.2 times more than the patients with higher economic status (HR = 1.20, %95 CI 1.16–1.25)(55). Patients' lower economic status was related to their jobs and incomes, and to their less accessibility to medical facilities in rural areas and small towns which have led to the late diagnosis of the CRC in its advanced stages and an increase in the treatment costs and a decrease in their survival rate. However, the increase in the Spanish, Japanese and Chinese patients' mortality rate who live in the USA didn't show any significant difference with regard to their economic status (58). Early diagnosis, progressive and helping treatment in the early stages of the cancer and valid tumor grade classification are effective factors on the patients' survival rate.
Treatment quality and its availability, better economic status, diagnosis in the early stages of the disease alongside the type of the treatment are influential factors on the CRC patients' survival rate and clinical trials or meta-analysis studies can investigate the outcomes of the type of the treatment based on different stages of the disease well.