Tumor Recurrence and Follow-Up


Normal findings

Recurrence

Low signal intensity fibrosis

Retained seminal vesicles

Metallic clips

Residual prostate

Prominent venous plexus

Postoperative collections (lymphocele, hematoma, urinoma, abscess)

Nodular soft tissue mass of intermediate signal in prostatic bed

Fast and avid enhancement of nodule

Focal restricted diffusion

Elevated choline on soft tissue



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Fig. 7.1
Normal post-prostatectomy bed. (a) Sagittal and (b) axial T2WI showing the urinary bladder neck pulled down and anastomosed to the membranous urethra. Axial plane shows the anastomosis (arrows) with a uniform shape, symmetrical with low signal intensity


After radical prostatectomy, PSA should be theoretically undetectable. Officially, a patient will be having a biochemical failure when the PSA concentration exceeds 0.2 ng/mL [10].

MRI features of normal postoperative fibrosis include low signal intensity in all sequences in the anterior sphincter and rectal wall (Fig. 7.1). Retained seminal vesicles are observed in approximately 20% of patients after prostatectomy [11]. Recognition of normal residual seminal vesicles is of paramount importance [12], because such recognition prevents biopsies for erroneous suspicion of recurrent tumor (Fig. 7.2). Thus, biochemical failure occurs in about 70% of patients with residual seminal vesicles.

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Fig. 7.2
Normal retained seminal vesicles. (a) Axial and (b) coronal T2WI shows bilateral retained seminal vesicles (long arrows), with the typical convoluted tubular appearance of the seminal vesicles. There is also an incidental cyst (short arrow) anterior the retained right seminal vesicle in 63-year-old man with a PSA of 0.7 ng/ml

Pelvic lymphadenectomy may be performed, but this is not mandatory. Lymphoceles may occur at the site of lymphadenectomy and are found along the anatomic lymph node chains within the pelvis and the para-aortic region. Lymphoceles should not be confused with other postoperative complications such as urinoma, hematoma, abscess, or necrotic lymphadenopathy. Surgical clips may produce susceptibility artifacts and especially on dynamic contrast gradient-echo sequence [3].

Local recurrence can be suggested with the presence of soft tissue in the prostatectomy bed that is isointense to muscle on T1-weighted images and slightly hyperintense, intermediate signal to muscle on T2-weighted images [13]. Recurrent tumor tends to enhance avidly in the arterial phase and wash out during the venous phase, while granulation tissue shows either no enhancement or mild enhancement in the late phase [14]. Moreover, local recurrence will show high signal on DWI with high b value and low signal on ADC map (Fig.7.3).

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Fig. 7.3
Post-prostatectomy recurrence. (a) Axial T2WI, (b) ADC color map, and (c) DCE on color map and the corresponding time/intensity curve show a soft-tissue mass on T2WI (arrow) of intermediate, slight higher signal than muscle in the anastomotic bed. ADC map (b) shows restricted diffusion as low ADC value as blue color (arrow). DCE shows an early uptake and washout pattern on (c) (arrow), consistent with recurrent disease at the vesicourethral anastomosis



7.3 Radiation Therapy (Table 7.2)


A serum PSA increase after radiotherapy is the best indicator of biologically active tumor [2, 10]. Whenever such an elevation of serum PSA after nadir has taken place, imaging is required to investigate whether this increase is caused by local or systemic recurrent disease. After external-beam radiotherapy (RT), prostatic tissue demonstrates diffuse low signal intensity within all the gland on T2-weighted MR images (Fig. 7.4), which hinder tumor detection. Multiparametric assessment will help to detect recurrence [14] showing higher levels of choline, hypervascularity on DCE [15] and restricted diffusion on DWI, and the corresponding ADC map within a nodular lesion (Fig. 7.5). It is helpful to know the previous location of the lesion to analyze the possible functional changes of the tumor (Fig. 7.6) in order to decide whether there is tumor recurrence [16].


Table 7.2
Radiotherapy













Normal findings

Recurrence

Gland atrophy with diffuse low signal on T2 WI

Focal low signal on T2 WI could be due to treated tumor

Periprostatic irregularity

Inflammatory changes on the pelvis

Fatty replacement on bone marrow

Focal and lower signal than normal prostate on T2 WI

Fast, avid enhancement and wash out

Restricted diffusion


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Fig. 7.4
MRI post-external-beam radiotherapy (RT) and brachytherapy. (a) Axial T2WI after external-beam RT shows decreased signal intensity throughput prostate, with loss of zonal differentiation. (b) Axial T2WI shows multiple radioactive seeds (arrow) implanted in the prostate with decreased signal intensity throughout the prostate which makes difficult to distinguish a tumoral lesion


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Fig. 7.5
Cancer recurrence post-external-beam radiotherapy (RT). (a) Axial T2WI after external-beam RT shows diffuse decreased signal without clear nodular lesion. (b) Axial ADC map shows marked low signal intensity in the right peripheral zone (arrow) with early and avid enhancement pattern on the axial dynamic contrast enhancement sequence on color map (c) (arrow), corresponding to a recurrent mass, which was biopsy-proven prostate cancer recurrence


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Fig. 7.6
Cancer recurrence post-external-beam radiotherapy (RT). (a) Axial T2WI after external-beam RT shows diffuse decreased signal with slight bulging on the right side without clear nodular lesion. (b) Axial color map postprocess of spectroscopy acquisition shows higher levels of choline within the right side demonstrated as color green, due to recurrence and proven on biopsy

RT may be delivered by means of brachytherapy, in which radioactive sources (seeds or needles) are implanted directly into the prostate gland (Fig. 7.4). The implants might be permanent or temporary. On permanent implants, spectroscopy imaging and DWI might be suboptimal because the metallic seed implants may create susceptibility artifacts and image distortion [17]. Therefore, DCE is a critical sequence in the multiparametric prostate MR exam in order to detect recurrence following permanent brachytherapy [18] and is characterized by an area of rapid contrast enhancement and early washout (Fig. 7.7). Temporary brachytherapy is not affected by susceptibility artifacts because no metallic material is retained; thus, all the multiparametric acquisition can be performed besides DCE, such as DWI and MR spectroscopy, to detect recurrence, with similar findings as described for external RT.

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Fig. 7.7
Cancer recurrence post-brachytherapy. Axial T2WI (left) shows multiple radioactive seeds (arrow) implanted in the prostate with decreased signal intensity throughout the prostate which makes difficult to distinguish a tumoral lesion. The corresponding axial dynamic contrast enhancement sequence (right) shows early and avid enhancement pattern in the right peripheral zone on two nodular lesions (arrows) corresponding to recurrent tumors, which were biopsy-proven prostate cancer recurrence


7.4 Androgen-Deprivation Therapy (Table 7.3)


The MR findings after androgen-deprivation therapy show diverse findings depending on the type (single therapy or combined agents) and duration of therapy [3]. The findings range from no changes with short-duration monotherapy to homogeneously reduced signal on T2-weighted images and decrease in prostate volume and size of the seminal vesicles. It is difficult to differentiate benign and malignant prostate tissue although the features of focal lower signal on T2-weighted images (Fig. 7.8), choline levels (Fig. 7.9), restricted diffusion, and hypervascularity (Fig. 7.8) can be combined. Functional sequences (DWI, DCE, and spectroscopy) are useful to monitorize treatment (Fig. 7.9) which are more accurate to evaluate response than the morphological sequences such as T2WI. Benign, inflammatory changes could be erroneously interpreted as recurrence on T2WI (Fig. 7.9).


Table 7.3
Androgen-deprivation therapy












Normal findings

Recurrence

Gland atrophy with diffuse low signal on T2 WI

No periprostatic irregularity

No inflammatory changes on the pelvis

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May 5, 2018 | Posted by in MAGNETIC RESONANCE IMAGING | Comments Off on Tumor Recurrence and Follow-Up
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