[Sentinel lymph node dissection in prostate cancer. Experience after more than 800 interventions]

Sentinel node biopsy and lymphatic mapping in penile and prostate cancer

BACKGROUND

Nodal metastases are linked to poor outcome in men with penile or prostate cancer. Early detection and resection are important for staging and for the prognosis. However, lymphadenectomy is associated with morbidity and may miss metastases when performed solely on the basis of anatomical templates.

METHODS

In this article we describe the technique and benefits of sentinel node biopsy (SNB) and provide a review of the literature.

RESULTS

Dynamic sentinel node techniques using both radioactive and optical (hybrid) tracers have been proven effective in penile cancer. For prostate cancer, SNB added to extended nodal dissection may further tailor dissection to the highly variable lymphatic drainage patterns in the pelvis. The sensitivity of SNB was found to be superior to conventional imaging methods; however, false-negative SNB procedures can occur and a complementary extensive lymphadenectomy is required to remove additional positive nodes that were not detected in the SNB template.

CONCLUSION

SNB is a standard method for early detection of nodal metastases in penile cancer and provides superior diagnostic accuracy to conventional imaging modalities in prostate cancer.

Preclinical evaluation of robotic-assisted sentinel lymph node fluorescence imaging

An ideal substance to provide convenient and accurate targeting for sentinel lymph node (SLN) mapping during robotic-assisted surgery has yet to be found. We used an animal model to determine the ability of the FireFly camera system to detect fluorescent SLNs after administration of a dual-labeled molecular imaging agent.

METHODS

We injected the footpads of New Zealand White rabbits with 1.7 or 8.4 nmol of tilmanocept labeled with (99m)Tc and a near-infrared fluorophore, IRDye800CW. One and 36 h after injection, popliteal lymph nodes, representing the SLNs, were dissected with the assistance of the FireFly camera system, a fluorescence-capable endoscopic imaging system. After excision of the paraaortic lymph nodes, which represented non-SLNs, we assayed all lymph nodes for radioactivity and fluorescence intensity.

RESULTS

Fluorescence within all popliteal lymph nodes was easily detected by the FireFly camera system. Fluorescence within the lymph channel could be imaged during the 1-h studies. When compared with the paraaortic lymph nodes, the popliteal lymph nodes retain greater than 95% of the radioactivity at both 1 and 36 h after injection. At both doses (1.7 and 8.4 nmol), the popliteal nodes had higher (P < 0.050) optical fluorescence intensity than the paraaortic nodes at the 1- and 36-h time points.

CONCLUSION

The FireFly camera system can easily detect tilmanocept labeled with a near-infrared fluorophore at least 36 h after administration. This ability will permit image acquisition and subsequent verification of fluorescence-labeled SLNs during robotic-assisted surgery.

A comprehensive overview of radioguided surgery using gamma detection probe technology

The concept of radioguided surgery, which was first developed some 60 years ago, involves the use of a radiation detection probe system for the intraoperative detection of radionuclides. The use of gamma detection probe technology in radioguided surgery has tremendously expanded and has evolved into what is now considered an established discipline within the practice of surgery, revolutionizing the surgical management of many malignancies, including breast cancer, melanoma, and colorectal cancer, as well as the surgical management of parathyroid disease. The impact of radioguided surgery on the surgical management of cancer patients includes providing vital and real-time information to the surgeon regarding the location and extent of disease, as well as regarding the assessment of surgical resection margins. Additionally, it has allowed the surgeon to minimize the surgical invasiveness of many diagnostic and therapeutic procedures, while still maintaining maximum benefit to the cancer patient. In the current review, we have attempted to comprehensively evaluate the history, technical aspects, and clinical applications of radioguided surgery using gamma detection probe technology.

Does intensity modulated radiation therapy (IMRT) prevent additional toxicity of treating the pelvic lymph nodes compared to treatment of the prostate only?

BACKGROUND

To evaluate the risk of rectal, bladder and small bowel toxicity in intensity modulated radiation therapy (IMRT) of the prostate only compared to additional irradiation of the pelvic lymphatic region.

METHODS

For ten patients with localized prostate cancer, IMRT plans with a simultaneous integrated boost (SIB) were generated for treatment of the prostate only (plan-PO) and for additional treatment of the pelvic lymph nodes (plan-WP). In plan-PO, doses of 60 Gy and 74 Gy (33 fractions) were prescribed to the seminal vesicles and to the prostate, respectively. Three plans-WP were generated with prescription doses of 46 Gy, 50.4 Gy and 54 Gy to the pelvic target volume; doses to the prostate and seminal vesicles were identical to plan-PO. The risk of rectal, bladder and small bowel toxicity was estimated based on NTCP calculations.

RESULTS

Doses to the prostate were not significantly different between plan-PO and plan-WP and doses to the pelvic lymph nodes were as planned. Plan-WP resulted in increased doses to the rectum in the low-dose region </= 30 Gy, only, no difference was observed in the mid and high-dose region. Normal tissue complication probability (NTCP) for late rectal toxicity ranged between 5% and 8% with no significant difference between plan-PO and plan-WP. NTCP for late bladder toxicity was less than 1% for both plan-PO and plan-WP. The risk of small bowel toxicity was moderately increased for plan-WP.

DISCUSSION

This retrospective planning study predicted similar risks of rectal, bladder and small bowel toxicity for IMRT treatment of the prostate only and for additional treatment of the pelvic lymph nodes.

Reliability of preoperative diagnostics and location of lymph node metastases in presumed unilateral prostate cancer

OBJECTIVE

To investigate the reliability of preoperative diagnostics in predicting the true histopathological stage and grade of prostate cancer, and to examine whether lymph node (LN) metastases in unilateral prostate cancer are located unilaterally and therefore whether it is justified to dissect only the ipsilateral LNs in presumed unilateral disease.

PATIENTS AND METHODS

LN metastases in clinically localized prostate cancer are often located near the internal iliac vessels. They will be detected by extended or sentinel pelvic LN dissection (PLND). Both techniques might be time-consuming and require extensive surgical experience. In all, 564 men with impalpable or unilateral palpable prostate cancer and positive biopsy cores only in one prostate lobe had a radical prostatectomy (RP) combined with radio-guided PLND and in some cases an extended PLND.

RESULTS

A median of six sentinel LNs (mean, seven) and six non-sentinel LNs (mean, seven) were dissected per patient; 52 of 564 men (9.2%) had positive LNs. Most men with unilateral disease had LN metastases on the same side of the pelvis. Comparing the clinical stage and grade with the tumour stage and grade of the RP specimen, there was a high percentage of upstaging and upgrading even in men with only one positive biopsy core.

CONCLUSION

Unilateral prostate cancer preferentially metastasizes to the ipsilateral pelvic LNs. Because there are a few cases of bilateral LN metastases even in unilateral disease, and as it is not possible to reliably predict unilateral disease on the basis of biopsy features, PLND only on the tumour-bearing side has a high risk of understaging, and would possibly leave LN metastases behind.

Optimized coverage of high-risk adjuvant lymph node areas in prostate cancer using a sentinel node–based, intensity-modulated radiation therapy technique

PURPOSE

Irradiation of adjuvant lymph nodes in high-risk prostate cancer was shown to be associated with improved rates of biochemical nonevidence of disease in the Radiation Therapy Oncology Group trial (RTOG 94-13). To account for the highly individual lymphatic drainage pattern we tested an intensity-modulated radiation therapy (IMRT) approach based on the determination of pelvic sentinel lymph nodes (SN).

METHODS AND MATERIALS

Patients with a risk of more than 15% lymph node involvement were included. For treatment planning, SN localizations were included into the pelvic clinical target volume. Dose prescriptions were 50.4 Gy to the adjuvant area and 70.0 Gy to the prostate. All treatment plans were generated using equivalent uniform dose (EUD)-based optimization algorithms and Monte Carlo dose calculations and compared with 3D conventional plans.

RESULTS

A total of 25 patients were treated and 142 SN were detectable (mean: n = 5.7; range, 0-13). Most SN were found in the external iliac (35%), the internal iliac (18.3%), and the iliac commune (11.3%) regions. Using a standard CT-based planning target volume, relevant SN would have been missed in 19 of 25 patients, mostly in the presacral/perirectal area (22 SN in 12 patients). The comparison of conventional 3D plans with the respective IMRT plans revealed a clear superiority of the IMRT plans. No gastrointestinal or genitourinary acute toxicity Grade 3 or 4 (RTOG criteria) occurred.

CONCLUSIONS

Distributions of SN are highly variable. Data for SN derived from single photon emission computed tomography are easily integrated into an IMRT-based treatment strategy. By using SN data the probability of a geographic miss is reduced. The use of IMRT allows sparing of normal tissue irradiation.