Results of a recent study indicate that obesity does not negatively affect outcomes after stem cell transplantation in multiple myeloma patients. In fact, obese patients treated with high-dose melphalan-based chemotherapy and total body irradiation before transplantation had a lower risk of relapse and better overall survival, compared to normal-weight patients.

The study authors concluded that obese multiple myeloma patients should not be excluded from stem cell transplantation due to their weight.

“Obese patients don't seem to be at higher risk for severe side effects from transplant compared to patients of normal weight, and they don't seem to have worse outcomes from a myeloma perspective either. Autologous transplants remain an important consideration as part of myeloma therapy for all patients,” said Dr. Dan Vogl of the University of Pennsylvania and lead author of the study.

Dr. Vogl and his colleagues suggested that further studies be conducted to determine the optimal dosing of both chemotherapy and total body irradiation in obese patients.

A standard therapeutic approach for younger patients with newly diagnosed myeloma involves high-dose chemotherapy followed by stem cell transplantation. In this procedure, a patient’s stem cells are first collected. After undergoing high-dose chemotherapy, the patient receives the collected stem cells to replace any cells that were damaged from the chemotherapy.

Although stem cell transplantation has been shown to benefit younger patients, there are many factors that may impact and vary treatment outcomes, including the patient’s weight. According to the study authors, it is important for physicians to factor in obesity when making treatment decisions, as obese patients may need altered chemotherapy dosing or may have other diseases in addition to myeloma.

However, there is currently limited data available about the role of obesity in myeloma patients undergoing stem cell transplantation to help guide the physicians’ treatment decisions.

In the current study, Dr. Vogl and his colleagues retrospectively analyzed data from 1,087 myeloma patients who underwent single stem cell transplantation between 1995 and 2003. The patients had received a melphalan ^[1] (Alkeran)-based preparative treatment with or without total body irradiation. The median age of the patients at transplantation was 57 years.

Using the patients’ body mass index (BMI), the researchers classified patients as normal weight (BMI between 18.5 and 25), overweight (BMI between 25 and 30), obese (BMI between 30 and 35), or severely obese (BMI above 35).

They found that the obese patients were generally younger than non-obese patients. In addition, the obese patients had a higher rate of diabetes, high calcium levels, severe low red blood cell counts, and kidney dysfunction.

For patients who received melphalan alone, the researchers found that BMI did not affect outcome after stem cell transplantation. The five-year progression-free survival rate was 14 percent in severely obese patients and 21 percent in obese patients, compared to 18 percent in overweight patients and 17 percent in normal-weight patients.

The researchers also found that severely obese patients were 30 times more likely than normal-weight patients to receive a reduced dose of melphalan, which the researchers defined as less than 90 percent of 200 mg/m². Obese patients were 11 times more likely to receive a reduced dose than normal-weight patients. However, the reduced dose did not affect progression-free survival.

Results also showed that obese and severely obese patients who received melphalan and total body irradiation prior to stem cell transplantation had improved progression-free survival and overall survival compared to normal-weight and overweight patients.  The five-year progression-free survival rate was 55 percent in severely obese patients and 43 percent in obese patients, compared to 23 percent in normal-weight patients and 17 percent in overweight patients.

The researchers pointed out that it is not clear at this point why obesity had a positive effect in patients treated with melphalan and total body irradiation but not in patients treated only with melphalan.

According to the study authors, the combination of melphalan and total body irradiation is no longer a common anti-myeloma regimen because melphalan alone produces similar results with fewer side effects. However, the findings in this study suggest that melphalan in combination with total body irradiation may be a feasible treatment option for obese patients.

The researchers added that additional research is needed to further examine the relationship between obesity and treatment outcomes.

“At [the University of Pennsylvania], we have been pursuing further research regarding chemotherapy dosing in obese patients. We are still analyzing data from our first study and have more studies planned, with a goal of eventually being able to truly individualize chemotherapy doses. This would ideally not just use rough measures like body size and composition, but also kidney function and genetic factors that could put people at higher risk of side effects or disease relapse,” said Dr. Vogl.

For more information, please refer to the article in Biology of Blood and Marrow Transplantation ^[2] (abstract).