22 Penis cancer

Penis cancer

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THE GEC ESTROHANDBOOKOF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 15/07/2022

For patients with either suspicion or histological evidence of inguinal lymph node extension, a 18-fluorodeoxyglucose Positron Emission Tomography/Computed Tomography (18-FDG PET/ CT) is recommended to assess for possible metastases to pelvic lymph nodes or distantly.

carcinoma) often treated with surface applicators, a 5 mmmargin at a depth is sufficient. For deeply infiltrating tumours, the whole glans should be included in the clinical target volume as there is no anatomical barrier in the penile glans, and it is difficult to assess accurately the extent of tumour invasion. The organs at risk during penile brachytherapy are the urethra and the testes. For intact tumours, the penile glans mucosa is part of the target volume as tumours usually develop from the surface of the penile glans. For postoperative indications, the mucosa may be considered as an organ at risk when the margin is not at the glans surface.

6. INDICATIONS, CONTRA-INDICATIONS

Discussion will focus on SCC although other pathologies can be considered for brachytherapy on an individual basis if technically suitable, even including oligometastatic disease to the penis from other primary cancers [15]. Generally, SCC under 4 cm confined to the glans or with limited involvement of the coronal sulcus would be considered suitable, provided coverage can be obtained with one plane of needles in addition to those required for treatment of tumour in the glans[16]. Larger tumours are associated with higher rates of necrosis, but still offer a reasonable chance of penile sparing. Circumcision is essential prior to undertaking any type of brachytherapy in order to fully expose the lesion and debulk that portion of the tumour which straddles the foreskin and the glans. In addition, if not removed, the foreskin is liable to both painful necrosis after brachytherapy, and phimosis which makes subsequent follow up difficult. Brachytherapy can be planned two weeks after the circumcision. In cases where the urethral meatus is involved, the interstitial needles should not be placed too close to the meatus as this risks subsequent meatal stenosis. Penile cancers on the shaft are much less common but still can be approached with brachytherapy, provided that “in transit” skipmetastases froma penile glans tumour are excluded, in which case total penectomy would be indicated. Superficial, and thus very low volume tumours, even if larger than 4cm in extent, may be suitable for surface mold brachytherapy. An interstitial implant in these cases is less desirable because it would involve treating the full thickness of the organ in order to cover a superficial rind of involved tissue. Lymph node status is the most important prognostic factor and lymph node management must be included in the initial treatment plan. Patients with a small volume primary and limited nodal involvement can still do well with a penile sparing approach. For patients with bulky nodal involvement, neoadjuvant treatment with chemotherapy or chemo-radiation is generally the preferred initial approach, as currently being investigated by the international InPACT trial (https://clinicaltrials.gov/ct2/show/NCT02305654). The role of brachytherapy can however be discussed according to tumour response, in order to avoid severe local symptoms from local progression.

8. TECHNIQUE

LDR template approach (also PDR) This is an in-patient technique performed under general or local anaesthesia (penile block) and requiring on average 5 days of hospitalization for treatment delivery at a classic low dose rate of 50-55 cGy/hour. Following induction of anaesthesia, the patient is catheterized with an in-dwelling Foley urinary catheter which will remain until treatment is completed. The tumour is then carefully examined and palpated to determine the number and spacing of needles and planes, and their orientation. This is facilitated by having various lucite templates available that are predrilled with needle spacings ranging from 12-15 mm. Generally, 2-4 planes of needles, and a total of 4-12 needles are required. The transparent templates are constructed to be 5 mm thick and can be placed over the tumour to more easily visualize the appropriate spacing and placement. 17-gauge steel needles are used for PDR after-loading, while 19.5 gauge needles were used for manually loaded Iridum-192 wire.The needles can be oriented either left-right (Figure 2), or from anterior to posterior (Figure 3), either unilaterally or bracketing the urethra, which can easily be palpated due to the presence of the urinary catheter. An exterior plane of needles that does not traverse tissue can be placed adjacent to the tumour, separated from it by tissue-equivalent bolus material such as superflab. This allows the superficial plane to be deep enough in tissue to avoid linear scarring or necrosis, while avoiding underdosing the surface of the tumour. A tumour that is primarily located on the dorsal or ventral surface of the glans will be preferentially approached with a left-right needle orientation. Reference 17 provides an illustrative summary of various implant approaches. We recommend beginning the needle insertion with the most distal, paracentral needles closest to the meatus. Once these are positioned through the chosen template, thematching exit template is placed, and the remaining needles are easily inserted. The templates are then snugged up against the penis and are adjusted to be parallel. The needles are adjusted so that the distance from the template to each needle hub is the same and the locking nuts are tightened. A Styrofoam or sponge collar is placed around the shaft of the penis proximal to the implant to distance the treated area from normal tissues. The implant procedure generally takes about 30-45 minutes. As the implant structure is rigid, and the geometry very stable over the duration of treatment, dose calculation can be done from measurements (Figure 4), or from a CT simulation. The penis should be oriented so that the CT is performed as transverse slices at right angles to the implant needles. Dilute contrast is placed in the urinary catheter to aid

7. TUMOUR AND TARGET VOLUME

The gross tumour volume (GTV) is defined clinically and radiologically. Clinical target volume (CTV) is defined as the gross tumour volume plus an anatomical margin of 1 cm in all directions. For very superficial tumours, without infiltration of corpus spongiosum (in situ tumours or non-invasive verrucous