Genitourinary Cancer

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SU_21_2210 - Prostate cancer upstaging by planning MRI and its impact on treatment decisions

Sunday, October 21
1:15 PM - 2:45 PM
Location: Innovation Hub, Exhibit Hall 3

Prostate cancer upstaging by planning MRI and its impact on treatment decisions
G. Mok, D. Duplan Jr, A. S. Gauthier-Pare, L. Igidbashian, V. Khahiri, Y. Benabu, and M. Alizadeh-Kashani; Hopital de la Cite-de-la-Sante, Laval, QC, Canada

Purpose/Objective(s): Planning magnetic resonance imaging (MRI) has shown potential in reducing radiation related toxicities for prostate cancer (PC) via improved prostate delineation. Utilization of MRI may also permit improved tumor detection and more accurate T-stage classification. However, it is unclear how to incorporate MRI detected changes in T-stage in clinical practice. Our purpose was to characterize how planning MRI changed T-stage and subsequent treatment-related decisions.

Materials/Methods: MRI planning was established at our centre in January 2016. All patients undergoing MRI planning for PC until January 2018 were analyzed. All patients were evaluated in consultation with a treatment recommendation prior to planning. NCCN guidelines were used for risk stratification. T1 and T2 images were fused to the planning CT simulation. Radiation planning was according to institutional guidelines. All MRIs were radiologist interpreted prior to completion of radiation planning. Treatment modifications based on MRI results were at the discretion of the treating radiation oncologist.

Results: 137 patients were included in this retrospective analysis. 79 patients (58%) had a different T-stage on planning MRI than clinical evaluation, of which 13 (10%) were downstaged and 66 (48%) were upstaged. 21 patients (15%) had an increase in their risk category with 17 of these patients moving from low/intermediate to high/very high risk categories. 16 of these 17 patients had discussions regarding modification of treatments with 6 patients (4%) altering the initial treatment plan based on MRI findings. 6 patients had hormone therapy added or prolonged; 4 patients had pelvic node irradiation; 2 patients had radiation dose modified.

Conclusion: Planning MRI interpretation by qualified radiologists can potentially impact treatment decisions. The application of MRI-based staging can potentially identify patients requiring more aggressive therapy, but may potentially lead to over-treatment of others. MRI results should be discussed with patients for informed decision-making.

Author Disclosure: G. Mok: None. D. Duplan: None. A. Gauthier-Pare: None. L. Igidbashian: None. V. Khahiri: None. M. Alizadeh-Kashani: None.

Gary Mok, MD

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