Multiparametric prostate MRI-based intensity-modulated radiation therapy guided by prostatic calcifications

Abstract

Objectives: The optimal technique to administer image-guided radiation therapy for prostate cancer remains poorly defined. This study assessed outcomes after multiparametric prostate MRI-based planning was delivered with image-guided radiation therapy using prostatic calculi observed on cone beam CT (CBCT). Methods: Between January 2015 and December 2017, 94 consecutive patients were treated with CBCT-based image-guided radiation therapy (IGRT) without fiducial markers. MRI was routinely incorporated for target delineation and intraprostatic tumor nodules were boosted to allow reduced doses to normal appearing prostate. The primary endpoint was the prevalence of prostatic calcifications while toxicity and biochemical control were secondary endpoints. Results: Median follow-up was 39.7 months with 82% NCCN intermediate to very high risk. Intraprostatic calculi were noted in 68% of patients. The 3-year biochemical control, late grade ≥2 rectal toxicity and late grade ≥2 urinary toxicity rates were 96%, 3 and 7%, respectively. Biochemical control and toxicity were not significantly impacted by the presence of prostatic calculi. Conclusion: Prostatic calcifications can serve as natural fiducial markers to allow for non-invasive IGRT for prostate cancer with promising early disease control and toxicity outcomes. Advances in knowledge: Prostate calcification-guided IGRT is technically feasible.

Analysis of risk factors for benign prostate enlargement with prostate calcification

“…Prostate cancer is one of the most frequently diagnosed malignancies among men worldwide, and prostate microcalcification has garnered attention as a potential prognostic marker for bone metastasis in this disease [11]. Previous research has indicated that while it often arises as a consequence of scar tissue formation following prostatitis resolution, several factors, including chronic prostatitis, prostatic urine retention, prostatic duct stenosis, abnormalities in calcium and phosphorus metabolism, and psychosocial factors, may contribute to its development [12][13][14]. Epidemiological studies have also linked poor dietary habits (such as irregular breakfasts and consumption of fatty snacks), alcohol consumption, and certain work-related habits (like prolonged sitting, late-night work, and the habit of holding in urine) to an increased risk of calcification [15,16].…”

QSM Throughout the Body

“…However, MRI only workflows are sought for because of the superior soft tissue contrast of MRI compared with CT and because they eliminate the risk for MR-CT registration errors as well as reduce the exposure of patients to ionizing radiation. [209][210][211] Conventional MRI workflows using magnitude data lack the ability to differentiate between diamagnetic calcification that are a common finding in the prostate, 212 fiducial markers such as gold fiducial markers that are more diamagnetic than calcification or titanium encapsuled seeds that are strongly paramagnetic, and blood products that possess a paramagnetic susceptibility. Therefore, the risk for error might outweigh the benefits of an MRI-only workflow.…”

“…Therefore, the risk for error might outweigh the benefits of an MRI‐only workflow 209 . Moreover, the use of prostatic calcification as an internal fiducial marker has been proposed 210 …”

“…209 Moreover, the use of prostatic calcification as an internal fiducial marker has been proposed. 210 A recent study showed that susceptibility values of gold intraprostatic fiducial markers were significantly different from the susceptibility values of intraprostatic calcification (P < 0.001), facilitating QSM-based radiotherapy planning and overcoming the limitations of magnitude-based MRI workflows. 213 Using an unsupervised k-means and k-medoids clustering machine learning algorithm, QSM-based automated detection of implanted low dose rate brachytherapy seeds could accurately detect seeds and estimate seed centroids while seed orientations were highly correlated with the actual orientations (R > 0.98).…”