How to prevent cervical cancer?

In patients with cervical cancer, lymph node metastases represent the most important prognostic factor for recurrence and poor survival. Metastases or micrometastases remained in lymph nodes are the explanation for development of secondary tumours and bad disease outcome. However, 15% of patients suffer from recurrent disease although their lymph nodes were free from histologically evident metastases (pN0). The presence in lymph nodes of patients with cervical cancer of occult tumour cells or tumour cell clusters smaller than micrometastases (<0,2mm) could be the reason of bad prognosis. Their role in cervical lymph nodes is still unknown and is currently being addressed in several studies. We have assessed an immunohistochemical approach and reverse transcription nested PCR (RT-PCR) for the detection of metastatic tumour cells in sentinel lymph nodes (SLN). IHC was done with a pan-reactive antibody against cytokeratines (AE1/3), an antibody against CK19 and an antibody against p16INK4A. The latter protein is invariably upregulatd in cervical cancers and is a surrogate marker of viral oncogene activity. Viral oncogene activity (HPVmRNA) was also directly detected by RT-PCR. A total of 120 SLN from 48 patients were analysed. There was a perfect agreement among all IHC markers, except CK19, for the detection of metastases and micrometastases. To differentiate micrometastases and metastases from tumour cells we set up a classification based on the size and number of detected tumour cells or clusters and micrometastases. Groups A, B, C, D were assigned as positive; respectively under Group A were included SLN with presence of micrometastases or metastases and under Group B, C and D were included SLN with present occult tumour clusters or cells smaller then micrometastases (<0,2 mm). Considerable discordance was observed for all markers for the detection of tumour cells clusters, multiple- and isolated tumour cells that respectively were classified under group B, C and D. There was no obvious differentiation between an artefact and an isolated tumour cell (Group D). Therefore, as expected, disagreement between the three markers was most evident at the single cell level (Group D). Discordance was also observed when comparing IHC with the RT-PCR. As expected, the best agreement of HPV mRNA (Fair Agreement: 0,009) was with the HPV surrogate marker p16INK4a. All results were influenced from usage of different parts of the LN tissue for the IHC and RT-PCR analyses; as a result sometimes tumour was present either in the part used for RT-PCR or in the one used for IHC staining. This pilot study clearly shows that a single marker is not specific enough for the reliable detection of occult tumour cells. Moreover, the non-random distribution of tumour cells in lymph nodes requires multiplesectioning to achieve higher sensitivity. In this regard molecular markers detected at the RNA level provide an obvious advantage.

Instructions

Difficulty: Challenging

1. Prognostic large clinical trials are needed to confirm the role of tumour cells or clusters smaller then 0,2 mm in cervical cancer outcome.
2. Subsequently, reliable tumour markers that are able to identify even isolated and sporadic occult tumour cells and clusters 0,2 mm could replace the markers that are currently being used in the routine for detection of LN micrometastases (H-E).
3. The “sentinel lymph node” concept for cervical cancer is still being researched.If this concept is valid for the CCa, then the cancer cells may appear in the SLN before spreading to other LNs, subsequently pelvine SLNs would be the ones that need to be examined for the presence of distant metastases, micrometastasis or tumor cells.