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Diffusion-weighted MRI in assessing adnexal masses and breast cancers

par Hottat, Nathalie
Président du jury Sculier, Jean-Paul
Promoteur Jani, Jacques
Co-Promoteur Cannie, Mieke
Publication Non publié, 2023-04-17

Thèse de doctorat

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Résumé :

ABSTRACTDiffusion-weighted magnetic resonance imaging (MRI) is a proven, quick, and noninvasive tech-nique which requires no ionizing radiation or contrast media administration and is able to de-tect, characterize and stage malignant tumors, and to monitor treatment response. Over the two last decades, many clinical applications of diffusion-weighted imaging (DWI) have emerged in the field of women’s oncology. This technique provides both qualitative and quanti-tative information offering a promising new tumor biomarker in clinical routine. This thesis work was therefore conducted to demonstrate the critical role of DWI in the man-agement of adnexal masses and breast cancers. The dissertation is divided into 5 chapters. Chapter 1 presents the general background. Chapter 2 is dedicated to the contribution of DWI in assessing adnexal masses. Chapter 3 is focused on the role of DWI in the evaluation of breast cancer response to neoadjuvant treatments with emphasis on the early response to neoadju-vant chemotherapy (NAC) and to neoadjuvant radiotherapy. Chapter 4 explores the performance of whole-body MRI (WB-MRI) including DWI in the initial staging of breast cancer patients at high risk of metastasis. Chapter 5 contains the discussion, future perspectives, and general con-clusion.Initially, we validated prospectively the ADNEX MR scoring system in the assessment of inde-terminate ovarian and adnexal masses with ultrasound (US) in 323 patients. We also evaluated a new, modified ADNEX MR scoring system that incorporates DWI including apparent diffusion coefficient (ADC) mapping. It showed an improvement of the classical ADNEX MR scoring sys-tem in diagnosing lesions with a score of 4 or 5 when adding DWI data analysis including ADC mapping, from 95.5% sensitivity and 86.6% specificity to 95.7% and 93.3%, respectively.Afterwards, we evaluated the added value of quantitative DWI in the diagnosis of indetermi-nate adnexal masses with US in a cohort of 163 patients with 201 adnexal masses. We meas-ured ADC with a region of interest (ROI) and ADC histogram after segmentation of the whole-lesion (WL) of malignant and benign adnexal masses, and we evaluated their value in the O-RADS MRI score. We showed that integrating ADC thresholds in O-RADS MRI score 4 may dis-criminate between low-to-indeterminate and intermediate-to-high malignancy risk groups. Otherwise, we assessed the role of DWI after one cycle of NAC in predicting the pathologic and radiologic responses in 48 patients with 50 breast cancers with two-dimensional ROI-ADC measurement and with three-dimensional WL histogram analysis of ADC obtained after seg-mentation. We showed that a significant increase in ROI-ADC values between MRI 1 (before NAC) and 2 (after 1 cycle of NAC) was predictive of pathologic complete response (pCR) and of radiologic complete response. Moreover, the ROI-ADC measurement method was superior to the WL-ADC measurement method.Furthermore, we compared ROI-ADC measurement with the Ki-67 proliferation index before and after NAC to assess ADC changes as a predictive marker of changes in Ki-67 index due to NAC in 47 patients with 49 invasive breast cancers. After NAC, a significant increase in breast cancer ADC value was observed, which predicted a significant decrease in the Ki-67 index in patients with radiologic response and in patients with pCR.Additionally, we studied DWI in the evaluation of tumor response after neoadjuvant preopera-tive radiotherapy in early-stage breast cancers. We also observed an inverse correlation be-tween ADC and Ki-67 index in 19 patients with 22 breast cancers.Finally, we proposed a prospective clinical trial evaluating the performance of WB-MRI includ-ing DWI in the initial staging of 45 breast cancer patients at high risk of metastases in compari-son with PET-CT as standard of reference. Correlations between outcomes of the two modali-ties for the M staging and interobserver agreement were almost perfect. The negative predic-tive value of WB-MRI in the diagnosis of bone metastases was 97%.In conclusion, after 6 years of prospective clinical work, we were able to propose a review of the literature on adnexal masses and breast cancers that summarized the contribution of DWI and opened new perspectives. Our work shows that MRI including DWI is a cornerstone in the management of female oncology patients, with great potential in the fields of pelvic MRI in assessing adnexal masses, breast MRI in monitoring breast cancer under neoadjuvant treat-ment, and WB-MRI in staging breast cancers. Further research is needed to assess the optimal strategies in staging and monitoring breast cancer patients with WB-MRI including DWI as a reliable complementary technique to PET-CT, especially in cases requiring repeat examinations, thereby avoiding multiple life-time doses of radiotracers, minimizing ionizing radiation, and saving costs.