Abstract
Objective. Infective endocarditis (IE) is a potentially short-term lethal condition. An association with malignancy could complicate diagnostic and therapeutic decisions. The questions to be answered are: (1) which type of malignancies are encountered; (2) how often has the association between malignancy and IE been described, and (3) what are thus far the diagnostic and treatment strategies for patients with both conditions. Methods. A literature search from 2010 to 2018 has been performed with the focus on IE and cancer/malignancy/neoplasm, as well as with risk factors for adverse outcome, when cancer was included in the analysis. Results. An association between digestive, respiratory and hematologic malignancy with IE has been observed in four large databases. The most important mechanisms for this association are a “port of entry” and immune suppression. Sixteen studies dealt with the effect of short and mid-term cancer on the outcome of surgery of IE in these patients. No uniform management strategy could be identified. It seems that a malignancy does not alter the short-term outcome for IE, although referral to a tertiary cardiac center and surgical treatment are less common for patients with known malignancy. Conclusions. Although there is an association between malignancy and IE, no treatment strategy has yet been developed for these patients. Short-term outcome of IE is unaltered by cancer. In most papers, the effect of cancer on mid-term survival is only significant in a univariate analysis, without being a predictor. The results indicate that cardiac surgery for IE should not be withheld in patients in whom a treatable malignancy has been found.
Introduction
Infective endocarditis (IE) is a devastating condition. The hospital mortality of IE varies but a recent review showed that fatality could be over 30%, even with optimal treatment [Citation1]. Surgery is often required, but if a contraindication is present in patients who would otherwise need this procedure, the outcome is worse [Citation2]. Malignancy is often lethal at a later stage. Therefore, presence of malignancy in these patients could be considered as a contraindication by some authors. Moreover, an association between IE and malignancy has been documented [Citation3,Citation4]. This is most prominent for colorectal neoplasms and IE caused by S. gallolyticus, previously known as Str. bovis, subtype 1 [Citation5–9], with an odds ratio up to 5. This incidence varies considerably, however. This could be due to different study designs (retrospective v. prospective, observational, case control and cohort studies). Enterococci have also been documented as an important microbial agent in IE [Citation8,Citation10,Citation11], but this is less, compared to S. gallolyticus [Citation8].
A port of entry (POE) in the colon is the main mechanism in the development of bacteremia and IE, in which several microbial features can operate. Bacterial pili [Citation12–14], adhesion to epithelial cells with formation of a biofilm [Citation7,Citation10,Citation15–17] as well as attachment to the components of the extracellular matrix of heart valves [Citation7,Citation10,Citation16,Citation17] promote the bacterial virulence. A POE can also be located in the skin [Citation18]. Bacterial survival after phagocytosis [Citation15] can also play a role in the pathogenesis of IE. Immune suppression itself, induced by chemotherapy, alcoholism, metastatic disease and old age [Citation4,Citation7,Citation19–21] are also important factors to take into account. In patients with hematologic malignancies, proposed mechanisms for development of IE are neutropenia with insufficient phagocytosis, abnormal B and T cells, central venous catheters serving as POE, splenectomy, and chemotherapy-related immune suppression. IE can develop with staphylococci, streptococci but also gram negative rods and fungi [Citation18].
Therefore in patients with IE with certain organisms, an occult malignancy should be suspected. If a malignancy is documented, this could complicate the decision making process in these patients with respect to referral to tertiary cardio-surgical centers and to surgery for IE itself. However, in other, more common cardiac diseases, cancer has been proven not to be a reason to defer from cardiac surgery [Citation22,Citation23]. The research questions therefore are: (1) which type of malignancies are encountered; (2) how often has the association between malignancy and IE been described and (3) what are thus far the diagnostic and treatment strategies for patients with both conditions.
Methods
To address the abovementioned research questions, a systematic literature search was performed. Following search entry terms were included in the Boolean searches in Web of Science and PubMed databases: “endocarditis AND cancer OR malignancy”, or “endocarditis AND mortality” or “endocarditis AND risk score” from 2010 to 2018. This period has been chosen as a trade-off between including a sufficient number of series at one hand and limiting the risk of including series with older and possibly obsolete treatment guidelines for IE at the other hand. Moreover, details about infected cardiac devices such as valve prostheses and pacemakers were also included. Congress abstracts, reviews, case reports and papers not dealing with the topic such as thrombotic or non-infective endocarditis, cardiac myxomas, and papers dealing with specific diagnostic techniques such as 18-F desoxyglucose and positron emission tomography were excluded. Papers were explored for the inclusion of cancer, malignancy or tumor in their titles and abstract, even if malignancy was not a part of the analysis of the management strategy for these difficult patients.
Using this strategy, 242 items for “endocarditis AND malignancy OR cancer” and 190 for “endocarditis AND risk score” in Web of Science could be retained and explored by title and abstract. Most of the articles explored the association between IE and cancer, only 14 manuscripts focusing on management strategy and on outcome in patients with this complex condition were retained and studied in detail. However, in none of these, malignancy was the primary focus, neither on the treatment strategy nor on the outcome of IE. Screening in PubMed using the same search terms yielded 439 resp. 160 articles. After a comparable selection according title and abstract, six articles were identified. Four of these were duplicate and two very recent manuscripts dealt with the effect of cancer on the outcome of IE and with the management strategy. Finally, this resulted in 16 articles, of which nine dealt with short-term outcome of cancer in IE, and eight with mid- to long-term outcome (one article studied both short and mid-term results). Furthermore, four nationwide database derived series of interest were also included. The inhomogeneity the identified manuscripts precluded a meta-analysis.
Results
The rather high incidence of cancer in general in IE patients is demonstrated by the data derived from four large databases. The first, Medicare Fee-for-service database shows a presence of cancer of 11–12% in elderly patients admitted for IE throughout the observation period between 1999 and 2010. This database contains annually about 40,000 patients [Citation3]. The type of malignancy in this survey, however, has not been specified. The second database, SEER confirms the high association between IE and most common cancers [Citation21]. For colorectal cancer (CRC), the cancer incidence in a time span of 90 days around the IE diagnosis, is 19.8 (17.0–22.6) per 100,000 person-months, for pulmonary carcinoma this is 5.7 (4.2–7.1), for prostate carcinoma this is 4.1 (2.8–5.4). For breast carcinoma, the incidence is 1.9 (1.0–2.8), which is lower than the incidence of 2.4 (1.5–3.2) found in patients without cancer. These results confirms the important role of CRC in IE patients, but other malignancies play also a role. In the third Danish national registry of patients and Danish cancer registry, the four largest groups of malignancy are digestive cancers, respiratory cancers, prostate cancers, and hematologic malignancies [Citation4]. In 8445 patients with IE, 997 cancers (11.8%) have been detected during a median follow-up of 3.5 years. This corresponds with an increased standard incidence rate (SIR) of 1.61 (1.51–1.71). This SIR is 8.03 (6.92–9.26) in the first 3 months after the diagnosis of IE, but lowers to 1.75 (1.43–2.12) between the 4th and the 12th month and reduces further after 1 year. All types of malignancies follow this pattern. However, in the first 3 months, the hematologic malignancies show a SIR of over 20, which is much higher compared to other common malignancies. Colon, prostate as well as lung cancer have a lower SIR compared to hematologic malignancies in the first 3 months. Thereafter, SIR is comparable. In accordance with the SEER database, the SIR for breast cancer is at all times low. The fourth and retrospective observational Taiwanese National health Insurance program shows that the incidence of cancer is 1.49 times higher in the IE cohort. The adjusted hazard ratio is 2.19 (1.98–2.42) and this is the highest for hematologic malignancies with a ratio of 3.76 (2.61–5.41). Uterine, esophageal, liver and CRC also have a ratio above 2. For breast cancer, this ratio is low [Citation9].
Nine papers dealt with the issue of the effect of malignancy on hospital outcome in IE (). In only one series, an effect of cancer on hospital mortality is detected, but this is in an unadjusted analysis of a subgroup of patients with cardiac device related IE and in patients with cancer, the infected device is removed less often [Citation24]. In eight other papers, there is no significant effect of cancer on hospital mortality in patients with IE [Citation25–Citation32]. Although in three of these series, in which cancer is not identified as predictor, transfer to a tertiary center [Citation26] or surgery is performed in a significantly less degree [Citation30,Citation31], even in patients in whom the malignancy is not advanced!
Table 1. Outcome, strategy in referral and treatment of patients with IE and cancer.
Nine papers studied the effect of malignancy on mid to long-term outcome in IE (). This effect is much less clear. In three papers, no effect at 6 months to 1 year could be discerned [Citation25,Citation33] and surgery for IE lowers mortality in any stage of cancer [Citation32]. In three other papers, cancer was identified as a factor in an univariate analysis, but was not identified as a predictor [Citation10,Citation34,Citation35]. In only two papers, cancer was identified as a predictor at a median follow-up of 6.3 years [Citation36] and at 12.5 years [Citation19]. In the latter article, however, cancer was part of an age-adjusted Charlson comorbidity index. This index also included prior heart failure, which has a proven unfavorable effect on mortality [Citation1]. Heart failure, therefore, is a major confounder for the effect of malignancy on the outcome. Metastatic disease was one of the main drivers of long-term mortality [Citation19]. In one paper [Citation37], the effect of malignancy was involved indirectly. In some series, cancer is commented upon, but without statistical analysis. Cancer did not alter the approach for IE [Citation38], or was not considered as contraindication for re-operative valve surgery in the context of IE [Citation39]. However, cancer amongst other factors was considered as an exclusion criterion for surgery. The 1-year mortality in this subgroup of patients was high [Citation2].
The interrelation between cancer and PVE or IE in presence of a pacemaker is also investigated. The rate of PVE in some series varies between 18% [Citation40,Citation41] and 26% [Citation34], but can be up to 29% in presence of enterococci [Citation10]. However, a relationship between a cardiac valve prosthesis in IE and cancer was not analyzed, except in two papers. In one series, the presence of a valve prosthesis or a pacemaker is related to an increased adjusted Charlson Comorbidity Index [Citation19]. In another series, PVE is lower in cancer patients compared to non-cancer patients [Citation32]. Some series include only patients with PVE, which precludes comparison with NVE in this context [Citation25,Citation38,Citation42,Citation43]. While the effect of a malignancy in IE on outcome received attention, the presence of such infected cardiac device is either not analyzed of specified in most series [Citation32,Citation40,Citation41,Citation44]. If analyzed, the presence of a cardiac device in IE has no effect on treatment policy in several series [Citation25–27,Citation44]. In one series, PVE had a negative effect on the outcome in a univariate analysis [Citation19], in another series, there was a trend, but the numbers were low [Citation45]. Remarkably, in one series, presence of a malignancy influenced treatment policy: in this type of patients, a biological valve prosthesis was preferred [Citation37].
Discussion
Association between IE and cancer
The answer to the two first questions is obvious. From the included series, it is clear that most malignancies are digestive, hematologic and respiratory. The association between malignancy and IE has been described extensively. This is especially true for IE by S. gallolyticus spp. callolyticus and colonic neoplasia. In the last decades, it has become clear that cancer plays an important role in the pathogenesis of IE, either by serving as a POE or by the associated immune suppression. Bacterial properties such as the capacity to adhere and to infiltrate into tissues also play a major role. Typing of the infective agent could give some clues about the malignancy. Genetic and biomolecular typing although important, [Citation13,Citation16,Citation46] was underperformed [Citation47]. However, some issues still need clarification: is carriage of S. gallolyticus stable [Citation47] or not [Citation10]? Is this microorganism carcinogenic or just a bystander [Citation4,Citation6,Citation13,Citation14,Citation47]? Could the effect of a colonoscopy be disentangled from the effect of the neoplasm itself [Citation21]? Apart from the port of entry (POE) in the colon, there are several other possible POE’s: the skin, oral [Citation7], biliary, urinary and female genital tract. A POE can be recognized in about three quarters of patients with IE, which can give a clue of the microorganisms involved [Citation48]. If other microorganisms are identified, such as S. aureus, other POE such as deep catheters should be suspected [Citation32].
Hospital mortality
The third question, about the diagnostic and treatment strategy, has rarely been the primary focus of the included papers. This seems to be a gap in the current knowledge. However, several papers included data of the effect of malignancy on the hospital and mid-to-long-term outcome of their patients with IE. Although the primary purpose of most of the included series was not to investigate the effect of mortality in this specific setting, it is obvious that the presence of a malignancy does not affect early mortality. However, a serious referral bias should be taken into account: it might be that many patients with a known history of malignancy or active malignancy were simply not referred to tertiary cardiac centers, from which most series have been derived. One study only reports about this policy in the analysis [Citation26]. No information concerning the referral policy was available from any other study. Moreover, oncologic patients sometimes receives less surgery even if this is indicated [Citation2,Citation30,Citation31]. An explanation might be that the surgical risk was perceived as too high incorrectly [Citation31]. Moreover, it is not easy to disentangle the effect of cancer and age on treatment policy for IE: the risk for many cancers is age-related and age as well as cancer are related to rejection for surgical treatment of IE [Citation49]. In one series only, an effect of cancer on short-term outcome for IE has been observed. This manuscript focused on cardiac device related IE. This is a specific population with a high median age of 71.2 years [Citation24]. Hence we can safely state that cancer has no effect on the in-hospital outcome.
Mid-to-long-term outcome
The prognosis of IE is often poor on short-term, while the prognosis of malignancy is mostly determined at mid-to-long-term. Therefore, it could be expected that the effect of cancer can only be seen in this time frame. In series exploring the results at 6 months to 1 year follow-up, cancer was not identified as an independent predictor. Two papers report a follow-up of 5 years or longer. In a long-term follow up of over 5 year, the effect of malignancy was clearly visible [Citation36], although cancer has not always been identified as an independent predictor [Citation35]. In one paper, malignancy was incorporated in the age related Charlson comorbidity index. This index included a history of heart failure and renal dysfunction, which also have been identified as major causes of mortality by themselves and are therefore confounders [Citation19]. For all these reasons, a diagnosis of cancer should not be an argument to withhold surgery. From the data seen in the included papers, it can be provisionally concluded that withholding surgery for IE worsens its prognosis [Citation31,Citation32]. In patients with IE and metastatic disease, however, prognosis is dismal. Although the findings are not surprising, it is worthwhile to perform a large-scale and detailed internationally registry focused on this type of patients to confirm the validity of the current provisional conclusion. Until its results appear, it seems wise to include an oncologist in the endocarditis team whenever this is appropriate. This should facilitate the decision-making. In case of IE with Str. gallolyticus, a colonoscopy should be performed. In every case with a proven malignancy in the past (or in presence of a treatable malignancy), IE should be treated according the guidelines [Citation50] in order to avoid an unjust denial of surgery (flowchart, ).
Figure 1. Flow chart for proposed management in patients with infective endocarditis and a malignancy.
Limitations
The most important limitation is the retrospective nature of most studies, which decreases the level of evidence. Another major limitation is the design of studies involving the management of infective endocarditis. Only two of the identified manuscripts have been designed to evaluate the effect of malignancy itself on the outcome, although is some cases it is included as a factor in the analysis. This makes complete inclusion of all relevant manuscripts uncertain. However, by using broad search terms, and more than one “entry”, this risk has been minimized. Nevertheless, any conclusion should be interpreted with caution. Furthermore, a bias can be introduced by age-effect, by referral policy to tertiary centers or recruitment or access to healthcare in case of IV drug users. Although the current method of searching carries the risk of missing valuable manuscripts, the included series indicate that surgery in many patients with IE and cancer is a valuable option. It should also be noted that in microbial-oriented manuscripts, colon polyps are sometimes grouped with carcinomas as colorectal neoplasia, that bacteremia and IE are not always distinguished and that S. bovis is still used instead of the more common term S. gallolyticus. Genotyping is not always performed. Moreover, the stability of the carriage of this microorganism and its oncogenic capacity is still a matter for research.
Conclusions
A previous or concomitant but treatable malignancy in patients with IE is rarely the primary focus for analysis, but it seems that this condition does not affect short-term outcome and has a modest effect on mid-term outcome. Nevertheless, surgery for IE is underperformed in these patients. Therefore, in patients with a history of a prior or a known treatable active malignancy, every effort should be made to treat IE according the existing guidelines. This insight should affect the referral policy and associated to it, the treatment modalities for IE in patients with cancer.
Disclosure statement
No potential conflict of interest was reported by the authors.
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