title: Value of diffusion weighted MR imaging as an early surrogate parameter for evaluation of tumor response to high-dose-rate brachytherapy of colorectal liver metastases.
abstract: BACKGROUND
  To assess the value of diffusion weighted imaging (DWI) as an early surrogate parameter for treatment response of colorectal liver metastases to image-guided single-fraction ¹⁹²Ir-high-dose-rate brachytherapy (HDR-BT).
  
  
  METHODS
  Thirty patients with a total of 43 metastases underwent CT- or MRI-guided HDR-BT. In 13 of these patients a total of 15 additional lesions were identified, which were not treated at the initial session and served for comparison. Magnetic resonance imaging (MRI) including breathhold echoplanar DWI sequences was performed prior to therapy (baseline MRI), 2 days after HDR-BT (early MRI) as well as after 3 months (follow-up MRI). Tumor volume (TV) and intratumoral apparent diffusion coefficient (ADC) were measured independently by two radiologists. Statistical analysis was performed using univariate comparison, ANOVA and paired t test as well as Pearson's correlation.
  
  
  RESULTS
  At early MRI no changes of TV and ADC were found for non-treated colorectal liver metastases. In contrast, mean TV of liver lesions treated with HDR-BT increased by 8.8% (p = 0.054) while mean tumor ADC decreased significantly by 11.4% (p < 0.001). At follow-up MRI mean TV of non-treated metastases increased by 50.8% (p = 0.027) without significant change of mean ADC values. In contrast, mean TV of treated lesions decreased by 47.0% (p = 0.026) while the mean ADC increased inversely by 28.6% compared to baseline values (p < 0.001; Pearson's correlation coefficient of r = -0.257; p < 0.001).
  
  
  CONCLUSIONS
  DWI is a promising imaging biomarker for early prediction of tumor response in patients with colorectal liver metastases treated with HDR-BT, yet the optimal interval between therapy and early follow-up needs to be elucidated.
authors.affiliation: Department of Radiology and Nuclear Medicine, Otto-von-Guericke University Magdeburg, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Wybranski
authors.forename: Martin
authors.initials: M
authors.lastname: Zeile
authors.forename: David
authors.initials: D
authors.lastname: Löwenthal
authors.forename: Frank
authors.initials: F
authors.lastname: Fischbach
authors.forename: Maciej
authors.initials: M
authors.lastname: Pech
authors.forename: Friedrich-Wilhelm
authors.initials: FW
authors.lastname: Röhl
authors.forename: Günther
authors.initials: G
authors.lastname: Gademann
authors.forename: Jens
authors.initials: J
authors.lastname: Ricke
authors.forename: Oliver
authors.initials: O
authors.lastname: Dudeck
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000032:analysis*; D001918:Brachytherapy / Q000379:methods*; D002277:Carcinoma / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D015179:Colorectal Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D038524:Diffusion Magnetic Resonance Imaging / Q000379:methods*; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000473:pathology; D008113:Liver Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000556:secondary; D008297:Male; D008875:Middle Aged; D009362:Neoplasm Metastasis; D011237:Predictive Value of Tests; D011379:Prognosis; D011859:Radiography; D011879:Radiotherapy Dosage; D013997:Time Factors; D016896:Treatment Outcome
chemical_list: D015415:Biomarkers