Feasibility of bremsstrahlung dosimetry for direct dose estimation in patients undergoing treatment with 90Y-ibritumomab tiuxetan.

PURPOSE: Radioimmunotherapy with (90)Y-ibritumomab tiuxetan has been used successfully used in the treatment of CD20-positive non-Hodgkin's lymphoma (NHL). Pretherapy imaging with (111)In-ibritumomab tiuxetan has been used in provisional dosimetry studies. Posttherapy imaging of (90)Y-ibritumomab tiuxetan for clinical use is appealing as it would simplify the data acquisition process and allow measurements of actual doses absorbed during treatment. METHODS: The study included 29 patients with non-Hodgkin's lymphoma, of whom 16 (group I) received a pretherapy (111)In-ibritumomab tiuxetan diagnostic study and (90)Y-ibritumomab tiuxetan treatment 1 week later, and 13 (group II) received only (90)Y-ibritumomab tiuxetan treatment. Planar imaging and blood sampling were performed in all patients. The doses absorbed by organs at risk were calculated using a whole-body average attenuation correction factor (relative dosimetry approach) and, in the case of the (111)In-ibritumomab tiuxetan image sets, also using organ-specific attenuation correction factors (absolute dosimetry method). Red marrow absorbed doses were based on gamma counting of blood samples. RESULTS: The estimated red marrow absorbed doses from (111)In and (90)Y data were equivalent. In all cases, the doses absorbed by organs at risk were found to be within prescribed limits. The relative dosimetry approach applied to both the (90)Y and (111)In data significantly underestimated the doses relative to those obtained with the (111)In absolute dosimetry method which is generally accepted as the reference method (MIRD 16). In the case of (111)In, the relative dosimetry approach values were highly correlated (R(2) = 0.61) with the reference method values. Relative dosimetry estimates may be adjusted multiplying by a correction factor of 2.8. The (90)Y-ibritumomab tiuxetan relative dosimetry data correlated poorly with the reference method values (R (2) = 0.02). CONCLUSION: Based on patient-specific dosimetry, the administered activity may be increased by an average factor of 2.4, indicating that most patients could be undertreated. The relative dosimetry approach based on planar imaging largely underestimates doses relative to reference values. Dosimetry based on planar bremsstrahlung imaging is not a dependable alternative to (111)In dosimetry.

Persistence of delayed adrenarche in boys with thalassemia.

5 years after a previous study, we followed up a group of thalassemic patients, determining DHEA-S levels in peripubertal age, with the aim of evaluating whether adrenarche maturation occurred in boys and advanced in girls. Furthermore, we evaluated the degree of bone mineral density (BMD SDS(BA)) and analyzed growth parameters calculating standard deviation score with respect to bone age (BA) of height (Ht SDS(BA)), sitting height (SH SDSBA), and subischial leg length (SLL SDSBA), body mass index (BMI) and the difference between the values of the previous and the present study (deltaBMI), thyroid function and serum markers of bone metabolism. Our results showed persistent lack of adrenarche (DHEA-S 25+/-9.5 microg/dl) in all 6 boys and the absence of pubertal signs at chronological age (CA) of 12.4+/-1.4 yr and BA of 11.1+/-1.1 yr. Only one boy, 6 months later, showed a testicular volume of 4 ml (Tanner stage G2) with an increase of DHEA-S value (181 microg/dl) at BA 12.8 yr. Body disproportion and severe degree of osteopenia (BMD SDSBA -2.41+/-0.5) were observed in all boys, even though Ht SDSBA (0.14+/-0.8) and markers of bone metabolism were within the normal range. No change in nutritional status was observed (deltaBMI 0.09+/-0.4 kg/m2). In contrast, all the thalassemic girls had DHEA-S values (172.7+/-97.7 microg/dl) within the normal range at BA 12.7 +/-0.6 yr that was similar to CA. Furthermore, the appearance of Tanner stage B2 occurred in each of them at BA, near to CA, of 10.4+/-0.9 yr, and menarche was observed in three of them at mean BA, near to CA, of 11.4+/-0.9 yr. Ht SDSBA was below normal range (-1.11+/-0.8), but SLL SDSBA and SH SDS(BA) values were reduced homogeneously, so that proportional body growth was observed. A significant change in nutritional status was observed (deltaBMI 2.69+/-0.9 kg/m2). Bone density value (BMD SDS(BA) -0.25+/-0.4) was in the normal range. There were no statistically significant differences between boys and girls for ferritin serum levels, blood consumption and desferrioxamine dosage. In conclusion, lack of change in nutritional status, measurable in the form of deltaBMI, but not BMI alone, considered an important physiological regulator of adrenarche, regardless of individual adrenal androgen secretion, could have a key role in the lack of adrenarche persisting in thalassemic boys during peripubertal age. Further follow up is necessary, in particular when boys reach puberty, because delayed adrenarche represents the most intriguing aspect in these patients.