European Urology

Letters to the Editor published online

Lymph node metastases are the main prognostic variable in patients with penile carcinoma, and the value of an early inguinal lymph node dissection in patients with nonpalpable inguinal lymph nodes has been shown [1]. Because current chemotherapy regimens are not able to cure patients with advanced penile cancer, the complete resection of primary tumours and any involved lymph nodes remains of paramount importance [2].

There remains an ongoing discussion about the assessment of lymph nodes and the modalities of lymph node dissection. Data about prognostic parameters for pelvic lymph node involvement are limited. Therefore, any attempt to find new diagnostic tools has to be appreciated.

Graafland et al. [2] report the diagnostic value of positron emission tomography (PET)/computed tomography (CT) for the diagnosis of ipsilateral pelvic lymph node disease in penile cancer patients with inguinal lymph node metastases. The authors report a sensitivity of 91%, with specificity of 100% and accuracy of 96%; however, we believe that there are several reasons why the authorsā€™ conclusions are not soundly supported.

The authors examined 21 patients, 3 of whom were excluded due to insufficient clinical data. For the remaining 18 patients, eight pelvic basins were excluded. This term refers to the authorsā€™ idea that patients can be divided into halves based on the notion that metastatic spread in penile cancer remains strictly ipsilateral. In our opinion, the idea that metastatic spread in penile cancer follows extremely reliable anatomic lines, from inguinal to ipsilateral pelvic to systemic, is unfounded. Indeed, Figure 3 in the paper by Graafland et al. [2] shows a case in which spread seems to have become systemic straight from the inguinal anatomy.

The notion of exact anatomic predictability of metastatic spread in penile cancer is an assumption that has not been proven. In our opinion, it makes no sense to exclude one anatomic half of the patient while the other half is included in an assessment of a diagnostic method for the evaluation for systemic disease, especially if the excluded eight basins in seven of eight cases belong to patients who have died of penile cancer in the meantime. We believe that if exclusions are necessary, whole patients must be excluded; hence, 20 basins would remain, amounting to 10 patients as a sensible basis for analysis.

In the retrospective assessment of a diagnostic technique, there should be very good reasons to exclude any patients at all. The excluded basins included several that had evidence of false-negative PET/CT findings (cases 5, 7, and 8 in Table 2 [2]); case 6 was apparently inadequately staged. If cases with unfavourable results for a new diagnostic method are excluded, then the resulting calculated sensitivity and specificity will be too high.

A further drawback of the study is that the follow-up of the included patients is not given. This hardly seems acceptable for the evaluation of a diagnostic method, since follow-up is the definite point that determines whether metastatic disease was missed or not.

Thus, the reported sensitivities and specificities appear unreliable, since >50% of the originally examined patients were excluded (11 of 21). This is regrettable, in itself, considering the low incidence of penile cancer. Furthermore, the prognostic value of PET/CT for the contralateral basins has to be further questioned because another four patients received chemotherapy.

One of the major break points for a diagnostic method used to assess potential lymphatic spread in cancer patients is the detection of micrometastases. PET/CT has been reported to be unable to detect metastases <2 mm; furthermore, only 16.7% of node metastases between 2 mm and 4 mm and only 66.7% of metastases between 5 mm and 9 mm were detected [3]. Thus, based not only on surgical node specimens but also on clinical follow-up, it is very unlikely that PET/CT will reliably achieve a sensitivity of >90% and a specificity of 100% for the detection of lymph node metastases in penile cancer patients.

Penile cancer patients with occult nodal spread face an extremely poor outcome after delayed lymphadenectomy, so the question of the apparent reliability of a diagnostic method becomes extremely important [1]. The aim of treating penile cancer patients, in our opinion, must be to come as close to potential cure as possible and not to be minimally invasive at all costs. Presently, pelvic lymph node dissection in penile cancer is considered mandatory in all patients with two or more inguinal lymph node metastases [5]. Additionally, in our opinion, younger patients with one affected inguinal node and those with very aggressive tumour subtypes require (and deserve) pelvic lymphadenectomy, regardless of PET/CT findings [2], and [4], until we have more definite evidence of the clinical reliability of PET/CT scanning in penile cancer patients.