DISCUSSION
This study, which had a relatively large cohort of patients who underwent surgery for colorectal cancer and were followed up for five years, showed a relationship between the fulfillment (or lack thereof) of some accepted diagnostic procedures or treatments employed during follow-up for this disease with certain adverse outcomes, such as mortality, recurrence, complications or changes in certain PROM scales.
The yearly performance of CT or colonoscopy in the follow-up of these patients is related to a lower risk of mortality but, on the other hand, a higher presence of complications and recurrences as well as further CT scanning, which may be explained because this type of diagnostic procedure continues to be used in surviving patients. Regarding PROM scales, a relationship was also seen with an increase in anxiety and a decrease in the total EORTC scores, which may reflect a deterioration in the HRQoL in the evolution of these surviving patients. On the other hand, the use of chemotherapy was related to higher mortality and increased presentation of complications or recurrences; radiotherapy, in this case, was only related to a higher risk of complications, perhaps due to a smaller sample size in which this treatment was employed. These treatments are expected to be used in patients with more severe degrees of the disease, which may explain the higher risk of mortality, recurrence or complications. In the case of radiotherapy, the four PROM questionnaires included detected losses in the patients’ health-related quality of life, while for chemotherapy, losses were found only in the EORTC-Q30. In any case, losses, as reflected by the beta parameter of the models, seem to be low losses and, from a clinical point of view, it seems that the deterioration in their quality of life is minor but the increase in their chances of surviving is high, but with a greater risk of complications and recurrences. By using these multivariable models, we try to show the influence of each of the procedures and treatments realized at each timepoint of follow-up on the clinical outcomes and PROMs of the next year of follow-up. Indeed, as different clinical outcomes and PROMs, as well as the main covariates, changed throughout the follow-up, an analysis that included all the repeated measurements and considered the longitudinal design was required to provide robustness to our results.
Our study tried to correlate just four (but some of the most relevant and common) quality indicators established for colorectal cancer patients with specific outcomes 1,10. Although we attempted in the analysis to control for some of the most relevant confounders, others could not be included. In any case, it is difficult to establish a clear cause-and-effect relationship between the study quality indicators and the outcomes, but we have tried to show that there are relationships between some of them and that those relationships are, in these pathologies, complex to interpret since, performing them are, on the one hand, saving lives, but, on the other hand, introducing the risk of different adverse outcomes, such as complications, recurrences or losses in patients’ quality of life11. In summary, the validation of these quality indices seems difficult to interpret because of complex results; therefore, the use of these diagnostic procedures or treatments as quality indices should be interpreted cautiously10,12.