Variations in the practice of molecular radiotherapy and implementation of dosimetry: results from a European survey

Abstract

Background: Currently, the implementation of dosimetry in molecular radiotherapy (MRT) is not well investigated, and in view of the Council Directive (2013/59/Euratom), there is a need to understand the current availability of dosimetry-based MRT in clinical practice and research studies. The aim of this study was to assess the current practice of MRT and dosimetry across European countries.

Methods: An electronic questionnaire was distributed to European countries. This addressed 18 explicitly considered therapies, and for each therapy, a similar set of questions were included. Questions covered the number of patients and treatments during 2015, involvement of medical specialties and medical physicists, implementation of absorbed dose planning, post-therapy imaging and dosimetry, and the basis of therapy prescription.

Results: Responses were obtained from 26 countries and 208 hospitals, administering in total 42,853 treatments. The most common therapies were ¹³¹I-NaI for benign thyroid diseases and thyroid ablation of adults. The involvement of a medical physicist (mean over all 18 therapies) was reported to be either minority or never by 32% of the responders. The percentage of responders that reported that dosimetry was included on an always/majority basis differed between the therapies and showed a median value of 36%. The highest percentages were obtained for ¹⁷⁷Lu-PSMA therapy (100%), ⁹⁰Y microspheres of glass (84%) and resin (82%), ¹³¹I-mIBG for neuroblastoma (59%), and ¹³¹I-NaI for benign thyroid diseases (54%). The majority of therapies were prescribed based on fixed-activity protocols. The highest number of absorbed-dose based prescriptions were reported for ⁹⁰Y microsphere treatments in the liver (64% and 96% of responses for resin and glass, respectively), ¹³¹I-NaI treatment of benign thyroid diseases (38% of responses), and for ¹³¹I-mIBG treatment of neuroblastoma (18% of responses).

Conclusions: There is a wide variation in MRT practice across Europe and for different therapies, including the extent of medical-physicist involvement and the implementation of dosimetry-guided treatments.

Keywords: Dosimetry; European survey; Molecular radiotherapy; Radionuclide therapy; Radiopharmaceutical therapy.

Fig. 1

Number of responding centers in different European countries. No responses were received from countries without numbers

Fig. 2

Replies for the questions a “Is a medical physicist involved in each treatment?”, b “Is the absorbed dose individually planned for each patient?”, c “Is post-therapy imaging performed?”, and d “Is post-therapy dosimetry performed?”. Numbers on the horizontal axis represent the percentage of the total number of responses for a particular therapy that gave the indicated reply

Fig. 3

Replies for the question “What basis of prescription do you typically use?”. a Therapies using ¹³¹I-NaI (A–E in Table 1). b Results for ¹³¹I-mIBG, ¹⁷⁷Lu /⁹⁰Y PRRT, and ¹⁷⁷Lu-PSMA (F–J in Table 1). c Therapies including radiation synovectomy, ¹⁵³Sm-EDTMP, ⁸⁹SrCl₂, and ²²³RaCl₂, ³²P sodium-phosphate, and ⁹⁰Y-ibritumomab-tiuxetan (M–R in Table 1). d ⁹⁰Y microspheres of resin or glass (K and L in Table 1). Numbers on the horizontal axis represent the percentage of the total number of responses for a particular therapy that gave the indicated reply. The vertical axis alternatives are numbered as listed in Table 1, where explanations of the abbreviations are given. Bar colors correspond to those in Fig. 2

Fig. 4

Percentage of responses from different countries who stated Always or Majority on the question “Is the absorbed dose individually planned for each patient?” for ¹³¹I-NaI treatment of benign thyroid diseases. Only countries represented by 3 or more responders are included