Benefits of High-Dose Vitamin D in Managing Cutaneous Adverse Events Induced by Chemotherapy and Radiation Therapy

Effects of Radiation Therapy on Vitamin D Levels

Unlike chemotherapy, studies on the association between radiation therapy and VD levels are minimal, with most reports in the literature discussing the use of VD to potentiate the effects of radiation therapy. In one cross-sectional analysis of 1201 patients with newly diagnosed stage I, II, or III colorectal cancer of any type (94% were adenocarcinoma), radiation plus surgery was associated with slightly lower 25(OH)D levels than surgery alone for tumor treatment 6 months after diagnosis (mean, −3.17; 95% CI, −6.07 to −0.28 nmol/L). However, after adjustment for demographic and lifestyle factors, this decrease in VD levels attributable to radiotherapy was not statistically significant compared with the surgery-only cohort (mean, −1.78; 95% CI, −5.07 to 1.52 nmol/L).¹⁸

Similarly, a cross-sectional study assessing VD status in 394 female patients with primary breast cancer (stage I, II, or III and T1 with high Ki67 expression [≥30%], T2, or T3), found that a history of radiotherapy was not associated with a difference in serum 25(OH)D levels compared with those with breast cancer without prior radiotherapy (odds ratio, 0.90; 95% CI, 0.52-1.54).¹² From the limited existing literature specifically addressing variations of VD levels with radiation, radiation therapy does not appear to significantly impact VD levels.

Vitamin D Levels and the Severity of Chemotherapy- or Radiation Therapy–Induced AEs

A prospective cohort of 241 patients did not find an increase in the incidence or severity of chemotherapy-induced cutaneous toxicities in those with suboptimal 1,25(OH)₂D₃ levels (≤75 nmol/L).²⁰ Eight different primary cancer types were represented, including breast and colorectal cancer; the tumor stages of the participants were not detailed. Forty-one patients had normal 1,25(OH)₂D₃ levels, while the remaining 200 had suboptimal levels. There was no significant association between serum VD levels and the following dermatologic toxicities: desquamation (P=.26), xerosis (P=.15), mucositis (P=.30), or painful rash (P=.87). Surprisingly, nail changes and hand-foot reactions occurred with greater frequency in patients with normal VD levels (P=.01 and P=.03, respectively).²⁰ Hand-foot reaction is part of the toxic erythema of chemotherapy (TEC) spectrum, which is comprised of a range of cytotoxic skin injuries that typically manifest within 2 to 3 weeks of exposure to the offending chemotherapeutic agents, often characterized by erythema, pain, swelling, and blistering, particularly in intertriginous and acral areas.^21-23 Recovery from TEC generally takes at least 2 to 4 weeks and may necessitate cessation of the offending chemotherapeutic agent.^21,24 Notably, this study measured 1,25(OH)₂D₃ levels instead of 25(OH)D levels, which may not reliably indicate body stores of VD.^7,20 These results underscore the complex nature between chemotherapy and VD; however, VD levels alone do not appear to be a sufficient biomarker for predicting chemotherapy-associated cutaneous AEs.

Interestingly, radiation therapy–induced AEs may be associated with VD levels. A prospective cohort study of 98 patients with prostate, bladder, or gynecologic cancers (tumor stages were not detailed) undergoing pelvic radiotherapy found that females and males with 25(OH)D levels below a threshold of 35 and 40 nmol/L, respectively, were more likely to experience higher Radiation Therapy Oncology Group (RTOG) grade acute proctitis compared with those with VD above these thresholds.²⁵ Specifically, VD below these thresholds was associated with increased odds of RTOG grade 2 or higher radiation-induced proctitis (OR, 3.07; 95% CI, 1.27-7.50 [P=.013]). Additionally, a weak correlation was noted between VD below these thresholds and the RTOG grade, with a Spearman correlation value of −0.189 (P=.031).²⁵

One prospective cohort study included 28 patients with any cancer of the oral cavity, oropharynx, hypopharynx, or larynx stages II, III, or IVA; 93% (26/28) were stage III or IVA.²⁶ The 20 (71%) patients with suboptimal 25(OH)D levels (≤75 nmol/L) experienced a higher prevalence of grade II radiation dermatitis compared with the 8 (29%) patients with optimal VD levels (χ²₂ =5.973; P=.0505). This pattern persisted with the severity of mucositis; patients from the suboptimal VD group presented with higher rates of grades II and III mucositis compared with the VD optimal group (χ²₂ =13.627; P=.0011).²⁶ Recognizing the small cohort evaluated in the study, we highlight the importance of further studies to clarify these associations.