Perineal recurrence of prostate cancer post-brachytherapy

We present a rare case of perineal recurrence of prostate cancer post low dose rate brachytherapy. Increased levels of prostate-specific antigen were recorded 12 years post brachytherapy. Pelvic CT and MRI visualized a nodular lesion in the perineum, and positron emission tomography demonstrated choline-avidity. Ultrasound-guided biopsy of the nodule was performed, yielding histology consistent with prostatic adenocarcinoma. Metastatic prostatic seeding to the perineum is a rare complication of brachytherapy. We discuss the putative mechanism, approach to diagnosis, and management.

He was subsequently monitored with serial PSA measurements as per NICE guidelines. 1 In May 2016, annual screening recorded an acute rise in PSA titre to 4.99 µg l −1 in the absence of new urinary or gastrointestinal symptomatology. The PSA titre increased further to 6.47 µg l −1 3 months later. He was investigated for disease recurrence. The PSA trajectory is outlined in Table 1.
investigations/iMaging Findings MRI of the prostate was performed including dynamic contrast-enhanced (DCE) imaging, which failed to identify tumour for targeted biopsy. Specifically, the prostate gland measured 4.9 × 2.7 × 3.3 cm in size (volume: 22.7 ml). Multiple brachytherapy seeds were visualised. The prostate gland demonstrated diffusely intermediate/low signal with no convincing areas of diffusion restriction (Prostate Imaging Reporting And Data System 2/5). On DCE, there were no areas of focal asymmetric pathological enhancement. The prostatic capsule and periprostatic fat planes were clear of metastatic spread. The seminal vesicles were atrophic. No significant pelvic lymphadenopathy was noted. There was no evidence metastasis in adjacent bones.
Despite negative MRI findings, persistently elevated PSA indicated biochemical failure, and in February 2017 prostatic biopsies were taken. Histology demonstrated only radiation-induced atypia. [ 11 C]-choline positron emission tomography (PET) was performed in October 2017 ( Figure 4). This revealed a choline-avid nodule in the base of the penis, within the perineum. The area corresponded to an area of soft tissue nodularity on pelvic CT, and a repeat We present a rare case of perineal recurrence of prostate cancer post low dose rate brachytherapy. Increased levels of prostate-specific antigen were recorded 12 years post brachytherapy. Pelvic CT and MRI visualized a nodular lesion in the perineum, and positron emission tomography demonstrated choline-avidity. Ultrasound-guided biopsy of the nodule was performed, yielding histology consistent with prostatic adenocarcinoma. Metastatic prostatic seeding to the perineum is a rare complication of brachytherapy. We discuss the putative mechanism, approach to diagnosis, and management.   MRI of the pelvis 2 months later was suspicious for recurrence of disease at the bulb of the penis ( Figure 5).
Ultrasound revealed a well-defined hypoechoic lesion at the base of the penis with posterior acoustic enhancement and some peripheral colour flow, correlating with the MRI findings ( Figure 6).
Biopsy of the lesion yielded histology consistent with recurrent prostatic carcinoma involving the base of the penis ( Figure 7A).
To confirm the diagnosis, a Tru-Cut biopsy was performed. This revealed moderately differentiated adenocarcinoma, Gleason 4 + 4 = 8 ( Figure 7B). CT of the chest abdomen and pelvis and bone scintigraphy confirmed absence of any further extra prostatic recurrence.

treatMent
Androgen suppression (Leuprorelin) was commenced and he was referred for consideration of Cyberknife therapy in light of oligometastatic disease. He was accepted for salvage treatment,

disCussion
Perineal recurrence of prostate cancer is a rare complication of LDR brachytherapy, with only two previous cases described in the literature. 2,3 6 years had elapsed between brachytherapy and perineal relapse in one case 3 and 4 years in the second. 2 Our case describes a patient who relapsed 10 years after initial treatment, with no other surgical interventions in the interim.
The postulated mechanism of action is seeding of malignant cells by the brachytherapy needles. A previous review of 502 patients with prostate cancer who underwent perineal biopsy demonstrated that five patients (1%) developed perineal seeding. 4 It appears to herald a poor prognosis: a subsequent case series by Moul and colleagues demonstrated that 100% of patients identified with seeding developed metastatic disease within 16 months, with a median survival of 36 months. 4 Risk factors conferring increased chance of seeding were reported as large tumour volume and the use of Tru-Cut biopsy. 5 Beyond perineal seeding, there is one reported case in the literature of bladder recurrence of prostate cancer post-brachytherapy presenting with biochemical failure. 6 In this case, review of the CT scan obtained for dosimetry at the time of brachytherapy demonstrated a lone catheter protruding through the bladder wall at the site of eventual recurrence.
In terms of management of the recurrent nodule, options depend on the patient's performance status, comorbidiy and preferences.
In the literature, one patient was treated with volumetric arc radiotherapy to the localized recurrence. 3 After multidisciplinary team discussion, our patient was commenced on luteinising hormone releasing hormone and referred for consideration of cyberknife ablation. The patient's anatomy was not amenable to surgical resection.
With increasing incidence rates of prostate cancer diagnosis 7 and subsequent treatment, the risk of iatrogenic complications such as that described in this case report will similarly rise. Moreover, improved survivorship of prostate cancer will increase rates of late complications of treatment. 8 Thus, clinicians should consider seeding to the perineum in patients with biochemical failure who have previously undergone bracytherapy. Future studies are required to determine whether prompt diagnosis and expedient intervention in these patients improves prognosis.