San Francisco, CA—Patients who undergo gastrectomy are at high risk for poor bone health and vitamin D deficiency and should be assessed and treated for this, according to researchers from Australia who described these issues at the 2016 Gastrointestinal Cancers Symposium.
When patients at the tertiary center in Sydney were identified and received appropriate treatment, vitamin D levels rose by at least 50% and osteoporosis rates dropped by 60%, said Robert Wilson, MD, a surgeon at the University of New South Wales, and Kiran Virik, MD, a medical oncologist at Launceston General Hospital in Australia.
Metabolic Bone Disease After Gastrectomy
Metabolic bone disease is a known but incompletely understood consequence of gastrectomy. In particular, osteoporosis, vitamin D deficiency, and secondary hyperparathyroidism occur frequently in long-term survivors, due to uncoupling of bone resorption and bone formation.
“Most of our patients were 5 years from surgery, and their biggest problem was not their cancer but the nutritional problems associated with their gastrectomy,” Dr Wilson said in an interview at their poster presentation. “They have weight loss, malnutrition, and vitamin D deficiency, and after surgery they avoid foods that upset them, like milk and meat. Also, the way reconstructions are done can worsen the problem with calcium absorption and vitamin D.”
“This is an underrecognized problem,” added Dr Virik. “We wanted to highlight the fact that while it’s great to cure cancer, it’s not so great if patients end up with very thin bones that could have been prevented with adjunctive therapies, like bisphosphonates.”
To understand more about the problem and its solutions, the researchers conducted a single-center study of 30 postgastrectomy patients, evaluating them with respect to bone health, postsurgical nutritional status, and osteoporosis diagnosis and management. In exploratory analyses they also looked at age, sex, histopathology, type of surgery, serum 25-OH vitamin D, calcium, parathyroid hormone (PTH), bone mineral density (BMD), vertebral x-rays, urinary calcium, and N telopeptide of type 1 collagen (NTx) excretion, along with other risk factors for these problems.
Patients’ median age was 67.5 years, and 73% of the patients were male. Their diagnoses were primarily gastric cancer (53%), esophageal cancer (20%), and gastric/duodenal lymphoma (7%). The patients had undergone total, partial/distal, or subtotal gastrectomies a median of 54.5 months before enrollment.
High Rate of Osteoporosis and Low Vitamin D Levels
Postgastrectomy osteoporosis was diagnosed in 19 (63%) and osteopenia in 9 (30%) of the study participants. Only 2 (7%) patients had normal BMD, the researchers reported.
Patients with 25-OH vitamin D deficiency were treated with oral vitamin D and calcium citrate replacement. Osteoporosis patients were treated with oral or intravenous bisphosphonates. Response to treatment was assessed by BMD studies, serum vitamin D and PTH levels, and urinary calcium and NTx excretion.
The researchers reported that identification and treatment of vitamin D deficiency paid off. At baseline, they documented vitamin D levels <50 nmol/L in 24 (83%) of 29 patients and <75 nmol/L in 28 (97%) of 29 patients, with mean levels of 35.1 nmol/L and 38.9 nmol/L, respectively. After vitamin D and calcium replacement, the mean vitamin D level rose to 81 nmol/L and improved to >50 nmol/L in 96% of patients and >75 nmol/L in 48%.
“Serum vitamin D levels above 75 nmol/L will optimize mineralization of bone and prevent excessive osteoid accumulation,” the physicians stated on the poster. “After a mean bisphosphonate treatment time of 4.5 years, only 1 of 14 patients had evidence of osteoporosis on BMD.”
Almost all patients with secondary hyperparathyroidism improved with vitamin D and calcium replacement. Unfortunately, despite nutritional intervention, osteopenic patients continued to have declines in BMD, the study found.
“Conversely, our patients with osteopenia, who did not qualify for bisphosphonates, had a reduction in total BMD and BMD in the femoral neck,” Dr Wilson said.
He emphasized the importance of this in a population that is primarily male. “Males start out with higher BMD than females, but they fracture at the same BMD levels. This means that if we just use T scores to assess risk in male patients, we may be underestimating their fracture risk,” he said. “That’s why our study used absolute BMD, rather than T scores, to look at response to treatment.”
Dr Virik said it would be important to have data showing that early intervention with bisphosphonates could prevent BMD loss in the osteopenic subset. Dr Wilson added that in osteopenic patients who got bisphosphonates, some improvement was noted.
“Whether bisphosphonate therapy will retard the progression of postgastrectomy osteopenia to osteoporosis merits future evaluation,” the researchers stated.
The investigators recommended that postgastrectomy patients be referred to an experienced dietitian for assistance with micro- and macronutrient deficiencies, and have BMD assessment at baseline and periodically, with interventions as needed.
Wilson R, Virik K. Bone loss and vitamin D deficiency post gastrectomy for gastro-esophageal malignancy. Poster presented at: 2016 Gastrointestinal Cancers Symposium; January 21-23, 2016; San Francisco, CA. Abstract 165.