1. Introduction
Immune checkpoint inhibitors (ICIs) are paramount in the treatment of various malignancies. However, while conferring an appreciable survival benefit, these agents also predispose patients to unique immune-related adverse events (irAEs), with diarrhea and colitis amongst the most common toxicities reported [
1]. Immune-mediated colitis (IMC) has been reported in up to 40% of patients treated with ICIs, varies widely in severity [
2,
3], and can be a cause for discontinuation of ICI therapy [
4]. Failure in early recognition and delayed or suboptimal treatment can lead to an increased risk of complications such as bowel perforation [
5].
The management of IMC involves the use of systemic steroids with selective immunosuppressive therapy (e.g., infliximab, vedolizumab) for CTCAE (grade of diarrhea) [
6] grade 2 or higher toxicity which has been found to achieve response rates of as high as > 80% [
7,
8]. Ustekinumab, tofacitinib, and fecal microbiota transplantation are also reported to be effective [
9,
10,
11] in treating steroid-refractory cases.
Inflammatory bowel disease (IBD) and IMC share multiple similitudes, such as the disruption in the immune surveillance pathways and gut homeostasis and consequent acute and/or chronic gastrointestinal inflammation [
9]. The clinical and endoscopic presentation of IMC is highly reminiscent of IBD and therefore, when considering the type of available treatments for IMC, one can infer that similar options are routinely used and recommended for IBD. One suggested treatment is budesonide, which has been shown to be efficacious in the induction of remission in IBD [
12,
13,
14,
15,
16].
Budesonide is an enteric-coated synthetic glucocorticoid which is absorbed in the distal small bowel where it undergoes extended first-pass metabolism from cytochrome P450 3A4 in the liver to compounds with negligible glucocorticoid activity (16α-hydroxyprednisolone and 6β-hydroxybudesonide) [
17] making it gut selective in action with minimal systemic side effects, in stark contrast to systemic corticosteroids. While a mainstay of IMC treatment, systemic steroids unfortunately bear several side effects including immunosuppression, adrenal suppression, weight gain, high blood pressure, hyperglycemia, etc. [
18] They also increase the potential risk for opportunistic infections and negatively affect anti-tumor immunity [
19]. Systemic immunosuppression is especially concerning as it could potentially worsen one’s response to ICI treatment and cancer prognosis. The use of budesonide as an alternative to systemic steroids for treating IMC could theoretically mitigate these risks while providing efficacious treatment for IMC; the use of budesonide for IMC was observed in a 39-patient cohort in which 13 patients received budesonide versus 25 receiving systemic steroids with no difference in terms of time from symptom onset to resolution and increased ICI cycles after being diagnosed with IMC [
20].
However, the use of budesonide for IMC is currently limited to less severe cases as recommended by the European Society of Medical Oncology guidelines [
21]. There is no available data on its role for long-term prophylaxis and/or as a bridge from systemic corticosteroids. Therefore, in this study, we aimed to study the efficacy and safety of budesonide as a therapy for IMC.
4. Discussion
IMC is the most frequently encountered toxicity secondary to immunotherapy and is often the reason for interruption in cancer care. Presently, high-dose corticosteroids form the backbone of the immunosuppressive treatment of this inflammatory toxicity that bears a striking resemblance to IBD, although additional immune-modulatory agents may be required for steroid-refractory cases, or for their steroid-sparing effect. [
20,
21]. However, systemic corticosteroids have a myriad of side effects which are particularly paramount in patients who are already immunosuppressed from their malignancies and cancer treatments. Our group has previously shown that the length of systemic steroid exposure can independently increase the risk of infection in a cancer patient population with a significantly higher risk when used for >30 days [
8,
22]. Furthermore, a recent systematic review assessing the safety profile of immunosuppressants in the management of irAEs which included 11 studies (1036 patients) showed that adverse events from irAE therapy occurred in about one-third of patients that received either systemic steroids or a combination of the same and other immunosuppressants [
5]. Burdett et al. [
23] showed that patients receiving steroids to treat irAEs had heterogeneous results regarding their cancer outcomes.
In contrast, budesonide bears a gut selective action in light of the drug’s first pass metabolism and pharmacokinetic profile, which significantly lowers systemic bioavailability (10–15%) [
24] and the potential side effects in comparison to systemic corticosteroids [
13] and this has been successfully employed in the management of IBD and autoimmune hepatitis. Studies demonstrate efficacious induction of remission with budesonide [
25,
26], administered orally at 9 mg daily for 6 to 12 weeks and tapered over 2 to 4 weeks. These patients were also noted to have a significantly lower adverse event rate, i.e., 37% compared to 62% in IBD patients treated with standard systemic steroids [
27]. Furthermore, bacterial and most viral infections occur less in budesonide-treated patients compared to patients treated with systemic glucocorticoids [
28]. These findings were redemonstrated in a systematic review and network meta-analysis of 31 trials including 5689 patients with IBD, wherein budesonide was associated with significantly fewer corticosteroid-related AEs than oral systemic corticosteroids [OR 0.25, 95% CI: 0.13–0.49] [
16]. Additionally, it has been shown that while both forms of steroid can induce remission in IBD, the gut selective form poses less suppression of pituitary-adrenal function [
13]. We therefore present data on the utility and safety of budesonide as a gut selective steroid in the management of these patients with IMC as an alternative to systemic corticosteroids.
Our sample was most representative of moderate severity IMC based on the CTCAE clinical grade and the majority with non-ulcerative inflammation on endoscopy (
Figures S1 and S2). More than half of our sample received budesonide exclusively with or without exposure to biologics and ~75% attained remission of colitis. Notably, our data demonstrates slightly improved results, nonetheless, in keeping with previous studies wherein the remission rate of IMC with corticosteroid use alone has been shown to be approximately 60–70% [
6,
7] among patients with moderate IMC. Our group has also demonstrated that an early introduction of selective immunosuppressive therapy (SIT) is associated with favorable clinical outcomes in patients with IMC with a decreased need for steroid exposure, fewer steroid tapering attempts and fewer hospitalizations [
8]. Robust data on the efficacy of the combination of SIT with budesonide in IMC therapy is lacking [
29,
30].
Another key finding in our analysis was that the duration of budesonide therapy in our sample was a median of 42.5 days, i.e., ~6 weeks, which is comparable, if not slightly better than the current practice with systemic steroids [
9,
31] which favors the use of the former given the gut-targeted effect and tolerable side-effect profile [
29,
30].
In our study population, the rate of developing diabetes, adrenal insufficiency or requiring long-term hydrocortisone after exposure to budesonide was low (2–9%) and less than what has been reported regarding systemic steroids as stated above. In regard to the two patients who developed diabetes after budesonide use: one was on chronic hydrocortisone and fludrocortisone for adrenal insufficiency and the other patient received a long course of prednisone and methylprednisolone for ICI pneumonitis. Moreover, with regards to diabetes and adrenal insufficiency, ICI use itself may serve as a confounding variable given its direct toxicity on the islet cells and adrenals [
32,
33,
34]. The infection sustained after exposure to budesonide may not be reflective of a true adverse effect in an immunocompromised patient.
At the end of our study period, ~55% of the cohort had progression of their cancer and approximately 42% had stable disease. However, the majority of our sample had stage IV disease prior to exposure to ICI. Despite multiple confounding factors and the lack of high-quality prospective randomized data, some suggest a decreased efficacy of ICI and worse clinical outcomes characterized by decreased overall and progression-free survival in cancer patients on ICI with exposure to systemic immunosuppression with corticosteroids and biologics in these patients [
35,
36,
37,
38,
39,
40,
41]. While this favors the use of a gut-targeting steroid with less bioavailability and systemic effects like budesonide, its outcomes on cancer specifically are yet to be studied.
Gut dysbiosis has been implicated in cases of IMC as well as cancer responsiveness to ICI and fecal microbiota transplant has been shown to be efficacious in the management of IMC refractory to the standard of care therapies [
11,
42,
43]. The relationship between budesonide and the gut microbiome has not been well studied. There is some data to suggest that in patients with microscopic colitis, the gut microbiome differs from healthy individuals and budesonide treatment restores the gut microbiome to that similar of healthy individuals [
44]. Larger studies to evaluate the effect of budesonide in conjunction with FMT on the gut microbiome may be beneficial to minimize immunosuppression in the cohort.
A small group of four patients in our cohort received budesonide as secondary prophylaxis for IMC and did well from a clinical standpoint. However, data in terms of using budesonide as a secondary prophylaxis to prevent recurrence is lacking; we do note that one clinical trial showed a lack of benefit of primary prophylaxis with budesonide in preventing IMC in patients with advanced melanoma treated with ipilimumab [
45]. Further investigation on the use of budesonide as secondary prophylaxis for IMC especially upon ICI re-challenge can be a new area of interest in future clinical practice.
Our study is not without limitations. This is a retrospective study that was conducted at a tertiary cancer hospital and may not be representative of other types of clinical practice. Our overall sample size is small which limits the power of subgroup analyses. Additionally, approximately 1/3 of our patients were treated with budesonide after being on systemic steroids, so this could affect the actual impact of budesonide on those patients.