In recent years, nephrology has been witnessing an increase in the care needs of patients with oncologic disease.1,2 For this reason, both nephrologists and oncologists believe that collaboration is needed to enable the optim[isation of care for these patients. Onconephrology is emerging as an increasingly complicated and rapidly growing field of medicine. The reasons for this are the higher prevalence of kidney complications in patients with cancer and also from the prevalence of cancer in patients with kidney disease.

In kidney disease associated with cancer is predominant the possibility of acute kidney injury (AKI), which is sometimes associated with nephrotoxic drugs3–6 and increases dramatically in the presence of pre-existing chronic kidney disease (CKD). Furthermore, some types of cancer and cancer treatment may also have deleterious effects on glomerular structure and cause proteinuria by damaging podocytes.7 The connection between cancer and the kidneys is broadened with kidney damage related to immunotherapy, electrolyte disorders, problems linked to chemotherapy doses and timing in patients with CKD on dialysis, partial or total nephrectomy in patients with cancer and CKD, and matters related to kidney transplantation (donors and recipients with a history of cancer).8

Onconephrology is already an established subspeciality in many hospitals. Many publications and international organisations, such as Kidney Disease Improving Global Outcomes (KDIGO), have suggested that this special care should be organised at leading oncology and nephrology centres.1,9–13 However, at present, there is no extensive, verified data on certain aspects such as the extent to which such practices would be frequented.

Some studies have already found that patients with cancer have a risk of AKI at one year of 17.5% and at five years of 27%,3 and a prevalence of stage 3 CKD of 12%.5 The impact on mortality is also noteworthy. The lower the glomerular filtration rate, the higher the mortality among patients with cancer.14

In addition, some studies have found that the lower the glomerular filtration rate, the higher the risk of onset of cancer. In general, a decrease of 10 ml/min in glomerular filtration rate increases the risk of cancer by 29%.15 In patients with renal replacement therapy on haemodialysis, the cumulative risk of developing tumours at five years has been estimated at 9.5%.16 Special mention must be made of the fact that patients who undergo kidney transplantation have a 2.1 times higher likelihood than the general population of developing cancer.17

The risk of AKI in patients with cancer during hospitalisation has also been demonstrated in several studies, with a longer hospital stay and a higher risk of complications also observed.1,18

The complexity of the relationship between the two types of disease (cancer and kidney disease) is increasingly evident and common, rendering a multidisciplinary approach essential for suitable and optimal management of the disease, as well as its prevention, treatment and complications. In addition, training of subspecialists in onconephrology and the establishment of dedicated practices should represent the initial point of support in early, comprehensive assessment of this patient group, both to prevent major complications and unnecessary hospital admissions and to develop areas of research among the different specialities in onco-haematology and onconephrology.

This study reviews the reasons for referring these patients, the characteristics of the multidisciplinary approach, the assessment of onconephrology patients and the situation of onconephrology practice in Spain. It also presents the limited experience to date in Spain with this type of practice, with a view to raising its profile, and identifies some requirements for its implementation.

In recent years, due to changes in various specialisations and in response to growing care needs, efforts to establish specialized dedicated centres have become more consolidated. In general, their objective has been to improve health results through, among other things, a cross-cutting approach to the disease in question, a decrease in clinical variability, and a better quality of care for patients with low-prevalence diseases, or in clinical situations that in many cases are more complex.

Specialities such as cardiology, pneumology and rheumatology have been implementing practices with these characteristics for the care of patients with specific diseases. Heart failure, chronic obstructive pulmonary disease, home oxygen therapy and arthritis are some examples of practices that have demonstrated their usefulness in the form of decreased numbers of hospital admissions and emergency episodes.19–23

Within nephrology itself, the development of advanced CKD units, as an example of dedicated practices, has been taking on more and more importance in nephrology services. The Sociedad Española de Nefrología [Spanish Society of Nephrology] recently presented the ACERCA project as a model for quality accreditation of these units.24 Unified results may be obtained based on the use of common standards. Up to now, unfortunately, objective data on this type of practice are not available, despite the time since establishment thereof at many hospitals in Spain.

In addition, within nephrology there is some other multidisciplinary experience, as in the case of patients with heart disease and kidney disease. These are complex patients whose concomitant heart failure and CKD benefit from a joint approach to treatment by both cardiologists and nephrologists. This practice may also be used in screening for heart disease with a view to kidney transplantation, with benefits reflected in lower mortality.25

The creation of onconephrology monographic consultations could therefore represent a clear benefit for patients in whom the approach to concomitant cancer and kidney disease proves complex. The possibilities of managing specific cases and quickly and efficiently contacting the referral onconephrology team would facilitate decision-making in this population and are viewed positively by the other specialisations involved.

The establishment of an onconephrology working group (ONCONEFRO) in 2018 within the Sociedad Española de Nefrología45 reflected recognition of the growing importance of this subspeciality in Spain and a commitment to implementing projects and studies in this area.

Between December 2018 and January 2019, the ONCONEFRO group conducted a survey to determine the current situation of onconephrology in Spain.

A total of 168 responses were received and nine hospitals that already had a dedicated practice as of January 2019 were identified: Hospital Clínic Universitari [University Clinical Hospital] (Valencia), Hospital Universitario Virgen del Rocío [Virgen del Rocío University Hospital] (Seville), Hospital Universitario Virgen Macarena [Virgen Macarena University Hospital] (Seville), Hospital Universitario Doce de Octubre [Doce de Octubre University Hospital] (Madrid), Hospital Clínic [Clinical Hospital] (Barcelona), Hospital Universitario Nuestra Señora de Candelaria [Nuestra Señora de Candelaria University Hospital] (Tenerife), Hospital Sant Joan de Déu [Sant Joan de Déu Hospital] (Barcelona), Clínica Universitaria [University Clinic] (Navarra) and Hospital General [General Hospital] (Alicante). The first two hospitals were the ones that had had a dedicated onconephrology practice for the longest period of time. Another nine hospitals also indicated that they planned to establish such a practice soon.

Despite the fact that 80% of those surveyed felt that onconephrology is an emerging subspecialisation that requires active participation by nephrologists, just 42% thought that it was possible to bring the project of open a monographic consultation for reasons of logistics and staffing.

Although such outpatient onconephrology clinics are known to have been established in other countries, preliminary data on outcomes are not yet available. In the United States, hospitals such as the MD Anderson Cancer Center in Houston, the Memorial Sloan Kettering Cancer Center in New York and the Dana-Farber Cancer Institute in Boston are increasingly adopting a more multidisciplinary model for cancer care.46

In Spain, we decided to analyse the initial data for a series of 199 patients from two hospitals with a monographic onconephrology consultations, assessed from the time of their establishment (Hospital Universitario Virgen Macarena in Seville, 161 patients, opened in October 2017, and Hospital Universitario Doce de Octubre in Madrid, 38 patients, opened in June 2018) to October 2019, with similar inclusion criteria at the two hospitals.

Tables 5 and 6 describe our series of patients in terms of baseline characteristics and kidney impairment characteristics.

Some differences between the population with solid tumours (n = 112) and the population with haematological disease (n = 87) were noted. For example, with regard to reason for referral, CKD was the main reason in the haematologic group (67%), followed by AKI (24%). In the case of the population with solid tumours, the percentages were similar (42% CKD versus 43% AKI).

These differences between the two population groups proved more significant when an aetiology of AKI and an aetiology of CKD were analysed separately. They are shown in Figs. 2 and 3. Notably, CKD of undetermined aetiology increased in the case of the population with haematological disease (18% of cases), probably due to the impossibility of performing kidney biopsy (comorbidities, high risk, advanced age in many patients with monoclonal gammopathy of renal significance, kidneys found to be unfit for biopsy on ultrasound, etc.).

Fig. 2.

Aetiology of acute kidney injury (%).

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Fig. 3.

Aetiology of chronic kidney disease (%).

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Regarding treatment, it should be noted that almost half the patients (49%) were on active cancer treatment when they were referred to the onconephrology practice. Of these, 38 required temporary suspension of this treatment due it its association with kidney impairment, 10 required permanent suspension without restarting any other treatment and 13 were switched to another line of treatment. Partial or complete improvement in kidney impairment in patients who underwent some sort of nephrologist-performed procedure occurred in 86 patients (86%). This reflects the importance of nephrology assessment in these patients.

Of the 199 patients, 25 underwent kidney biopsy (13%). The main pathology diagnoses were: monoclonal gammopathy of renal significance in seven patients (28%), paraneoplastic glomerular disease in six patients (24%), acute interstitial nephritis in four patients (16%) and tubulopathy due to cisplatin in one patient. In two cases, the diagnosis remained unclear even with biopsy, and in the five remaining patients (20%), the histology diagnosis was not related to the neoplastic disease/blood dyscrasia or the treatment thereof.

Overall, from a clinical point of view, a possible relationship between kidney disease and cancer was established in the different populations with solid tumours or haematological disease (Table 7). It was believed that there was no relationship between kidney disease and cancer in 38% of patients with solid tumours and 36% of patients with haematological disease. Kidney impairment was related more to haematological disease, strictly speaking, in 37% of cases and to cancer treatment (whether medical or surgical) in 40% of the population with solid tumours. There was a higher percentage of an unclear relationship in those with haematological dyscrasia/tumour (19%).

Finally, around 20% of patients referred to the practice died during the follow-up period. The leading cause of death was the cancer itself in 80% of cases. Infections, cardiovascular disease and terminal end stage chronic kidney disease corresponded to 6%, 6% and 3% of all other causes, respectively.

Based on our experience, there are no initial difficulties in establishing this type of practice. It is important to present the project to the other specialisations involved, in order to stress the value of collaborative work and introduce the referring "onco-nephrologist".

In general, hospitals' own experience with the practice has been satisfactory, both for the other specialisations involved and for the patients themselves.

The establishment of dedicated onconephrology practices results in better care of patients with cancer who develop an acute or chronic kidney abnormality or electrolyte disorder. However, it is subject to some requirements and recommendations. Individualised adaptation at each hospital will be essential for the success and continuity of the practice.

A multidisciplinary approach among the different specialisaties involved must be taken with the objective of optimising decision-making and engaging in suitable patient management overall. The patient's prognosis, quality of life, personal preferences and values must be borne in mind throughout the process, especially with regard to decisions around renal replacement therapy. Within nephrology itself, a joint approach with the kidney transplant and dialysis team is often needed.

The series of practices we analysed showed overall a high percentage of patients with CKD and AKI as reasons for consultation.

We observed a low number of kidney biopsies performed. As a possible explanation for this, in some cases kidney biopsy was deemed unnecessary due to the absence of a clinically justified connection between the patient's cancer and kidney disease. In a non-negligible percentage of patients, kidney biopsy was not performed as it was technically impossible (comorbidities or unfit kidneys).

Manifest differences were seen in aetiologies of AKI and CKD between the two patient groups. In the case of the group with solid tumours, there was a stronger relationship between kidney disease and cancer treatments used (medical or surgical). In the case of the group with dyscrasia, kidney impairment was related more to haematologic disease, strictly speaking.

Worthy of note was the confirmation that a high percentage of patients with kidney disease associated with neoplasia or blood dyscrasia benefited from assessment at the practice as it enabled optimisation of cancer treatment and amelioration of kidney impairment.

The establishment of unified, registered databases may be useful for analysing clinical data in daily practice and for conducting multicentre prospective studies. Onconephrology practices should be a starting point for the achievement of this objective on a national level and for the growing development of this emerging subspecialisation.

The authors declare that they have no conflicts of interest.