New methods and strategies for the diagnosis and treatment of pelvic lymph node metastasis of prostate cancer

The pelvic lymph nodes are a common site of prostate cancer spread. Unlike metastases to distant organs such as bones, lungs, and liver, prostate cancer with pelvic lymph node metastasis is still classified as regional lesions, which is between local and distant disseminated lesions.

1. Should local treatment be added to prostate cancer with pelvic lymph node metastasis?

Previous randomized controlled studies have confirmed that local treatment should be added to endocrine therapy for locally advanced prostate cancer. However, there are no data for prostate cancer with pelvic lymph node metastasis. In 2015, data from the National Cancer Database of the United States filled this gap. The authors divided the cases in the database into two groups: those receiving endocrine therapy alone and those receiving endocrine therapy plus local radiotherapy. The study showed that the 5-year overall survival rate was significantly improved in the endocrine therapy plus local radiotherapy group vs. the endocrine therapy alone group (71.5% vs. 53.2%).

At the same time, the authors conducted subgroup analysis based on age, tumor stage, Gleason score, and PSA to explore which group of patients would benefit more from the addition of local treatment. The results showed that the addition of local treatment significantly improved the survival of patients aged <65 years, T1~T2 stage, Gleason score 8~10 or PSA ≥20 ng/ml. For example, for patients with Gleason scores of 8 to 10, the 5-year survival rate was only 6% when receiving endocrine therapy alone, but it increased to 37% after adding local treatment, a difference of 31% (P=0.001).

Data from another population database also confirmed that patients with prostate cancer and pelvic lymph node metastasis had a better survival rate after radical prostatectomy, and the risk of death was reduced by 50% compared with endocrine therapy alone. Although there is still a lack of data from randomized controlled clinical studies, preliminary retrospective study data suggest that local treatment is the preferred option for prostate cancer with pelvic lymph node metastasis.

2. How to accurately detect pelvic lymph node micrometastasis?

Local treatment can improve the prognosis of prostate cancer with pelvic lymph node metastasis. However, not all prostate cancer patients have lymph node metastasis, so the formulation of local treatment plans depends on accurate pelvic lymph node assessment - confirming whether the lymph nodes have cancer metastasis before treatment.

Currently, the evaluation methods of pelvic lymph nodes are divided into three levels: conventional CT scan or MRI, tumor functional imaging choline PET/CT, and prostate cancer-specific imaging PSMA PET/CT. First, in terms of sensitivity, that is, the ability to accurately identify lymph node metastasis: the sensitivity of conventional CT or MRI is only 42%, and the addition of diffusion imaging can only increase the sensitivity to 57%; the sensitivity of choline PET/CT is slightly improved to 60%; and the latest PSMA PET/CT can be increased to 66%. This means that one-third of lymph node metastases are still missed. Secondly, the specificity of these examinations has increased from 82% for CT/MRI to 99% for PSMA PET/CT, which means that the probability of misdiagnosing lymph node metastasis is significantly reduced. Therefore, in terms of examination methods, although the diagnostic effectiveness of PSMA PET/CT is significantly improved compared to CT/MRI, its sensitivity still needs to be improved and it cannot replace the staging role of surgery.