Validating fPSA Glycoprofile as a Prostate Cancer Biomarker to Avoid Unnecessary Biopsies and Re-Biopsies

Round 1

Reviewer 1 Report

The paper describes that in PSA grey zone the combination of free PSA glycan information obtained using lectin-ELISA which the authors have developed with other clinical parameters improves detection of prostate cancer. Combining different data generally improves the accuracy of the diagnosis. However, for that purpose, it is necessary to make various measurements using different devices, which is not practical. This paper is excellent in that it shows the possibility that the PSA glycoprofiling can be applied to the current automatic measuring instrument in addition to free PSA and total PSA.

 

The authors should explain the following.

Line 72 and Line 162-164 (Supplementary Materials)

Fig. S1 in Line 72 does not show mass spectrometry.  The results from MALDI-MS are not shown anywhere.  The authors seem to analyze only normal fPSA.  It is unknown from which experiment by the authors the structure in figure S2 (B) was obtained.

Author Response

We thank the reviewer for his time spent reviewing our manuscript and his valuable advice for improvement. We have thoroughly revised our manuscript considering all the points rose as follows:

The paper describes that in PSA grey zone the combination of free PSA glycan information obtained using lectin-ELISA which the authors have developed with other clinical parameters improves detection of prostate cancer. Combining different data generally improves the accuracy of the diagnosis. However, for that purpose, it is necessary to make various measurements using different devices, which is not practical. This paper is excellent in that it shows the possibility that the PSA glycoprofiling can be applied to the current automatic measuring instrument in addition to free PSA and total PSA.

 

The authors should explain the following.

Line 72 and Line 162-164 (Supplementary Materials)

Fig. S1 in Line 72 does not show mass spectrometry. The results from MALDI-MS are not shown anywhere.  The authors seem to analyze only normal fPSA.  It is unknown from which experiment by the authors the structure in figure S2 (B) was obtained.

The result from the mass spectrometry experiment is now part of the Supplementary material file (see below, showing only the most abundant form of glycan detected besides the other ones).

 

At the same time, we now provide text showing that glycans structures shown in Fig. S3 were elucidated using mass spectrometry and SPR experiments together with extracting literature data.  

Author Response File: Author Response.pdf

Reviewer 2 Report

The authors performed a study on the role of fPSA glycoprofiling (PGI) on the diagnosis of prostate cancer. They concluded that Compared to PSA on its own, or fPSA% and the PHI, PGI showed improved discrimination between presence and absence of PCa and also in predicting clinically significant PCa.
the topic is interesting but has some limitations. 

Comments

 

- In the materials and methods the population studied is not very clear. I think a table with the clinical characteristics of the patients would help to better understand the results. how many patients had already done a biopsy?

 

-Also in the methods section you reported that the patients did a biopsy with 10 samples plus 5 targets. what does target mean? the patients had done a multiparametric magnetic resonance? this is not very clear. please specify

 

-what definition of clinically significant tumor did you use? please specify in the methods section.

 

-in your methodology, the patients performed an ultrasound-guided biopsy. since guidelines recommend the use of mMRI even in biopsy naive patients. I think this point should be reported as limit of your study.  

 

-Previous experiences have shown the use of mMRI increases the accuracy of markers such as PCA3, -2proPSA but also of total PSA. The accuracy of the MRI for primary diagnosis range between 0.80 and 0.90 in the various experiences. What can be the additional value of a marker such as the PGI. I think this is a crucial point of your experience and should be discussed.

 

-What about cost of PGI?

 

 

 

 

 

 

 

Author Response

We thank the reviewer for his time spent reviewing our manuscript and his valuable advice for improvement. We have thoroughly revised our manuscript considering all the points rose as follows:

 

The authors performed a study on the role of fPSA glycoprofiling (PGI) on the diagnosis of prostate cancer. They concluded that Compared to PSA on its own, or fPSA% and the PHI, PGI showed improved discrimination between presence and absence of PCa and also in predicting clinically significant PCa. The topic is interesting but has some limitations.

- In the materials and methods the population studied is not very clear. I think a table with the clinical characteristics of the patients would help to better understand the results. how many patients had already done a biopsy?

A: The cohort description has been extended and improved to improve clarity and understandability. The clinical data are summarized in the Table 1. Three non-cancer and 11 cancer patients had undergone previous biopsies with a non-cancer result. For all other patients it was the first prostate biopsy. This information is now also included in Table 1.

Lines 187-201:

“4.1. Clinical cohorts

Archived serum samples from 140 males who participated in the Tyrolean prostate cancer early detection program of the Department of Urology, Medical University Innsbruck, Austria, between 2013 and 2015 were used. All men underwent prostate transrectal ultrasound-guided prostate biopsy after presenting with elevated serum PSA. Clinical characteristics of study participants are summarized in Table 1.  The study was approval by the Ethics Committee of the Medical University Innsbruck, Austria (EK Nr: 1257/2017). Ten to 15 transrectal prostate core biopsies (10 systematic, up to five targeted by contrast-enhanced colour Doppler ultrasound and/or real-time sono-elastography [DOI: 10.1007/s00345-011-0809-6, 10.1111/j.1464-410X.2009.08963.x]) were sampled from each patient and analysed using standard histopathological procedures. Based on the biopsy results a cancer and a non-cancer cohort were chosen to fulfil the criteria of a “grey zone” serum PSA [7], while being age and tPSA level matched (Table 1). The level of PSA in the samples was within the range of 2-10 ng/mL (except for 1 sample in the non-cancer cohort, tPSA = 10.7 ng/mL). On the basis of prostate biopsy tumor grades the prostate cancer cohort was subdivided into low grade (low risk tumours, Gleason score 6) and significant, (high risk tumours, Gleason score ≥ 7) cancer sub-groups.”

 

-Also in the methods section you reported that the patients did a biopsy with 10 samples plus 5 targets. what does target mean? the patients had done a multiparametric magnetic resonance? this is not very clear. please specify.

A: Up to 5 targeted biopsies were taken on the basis of new ultrasound technologies, particularly contrast-enhanced colour Doppler ultrasound and real-time sono-elastography. This information is now also included in M&M. See above.

 

-what definition of clinically significant tumor did you use? please specify in the methods section.

A: Done: On the basis of prostate biopsy tumor grades the prostate cancer cohort was subdivided into low grade (low risk tumours, Gleason score 6) and significant, (high risk tumours, Gleason score ≥ 7) cancer sub-groups. Also included in Table 1.

 

-in your methodology, the patients performed an ultrasound-guided biopsy. since guidelines recommend the use of mMRI even in biopsy naive patients. I think this point should be reported as limit of your study. 

A: Indeed, we agree with the reviewer that this is a limitation of the study. Since this is a retrospective study using archived serum samples, no complete MRI data were available.  This is now included in the discussion.

Lines 180-182: “Recent guidelines for prostate biopsy recommend multi-parametric magnetic resonance imaging (mpMRI) also for biopsy naïve patients. In this retrospective study mpMRI data were not available for all subjects and were not considered, which is a limitation.”

 

-Previous experiences have shown the use of mMRI increases the accuracy of markers such as PCA3, -2proPSA but also of total PSA. The accuracy of the MRI for primary diagnosis range between 0.80 and 0.90 in the various experiences. What can be the additional value of a marker such as the PGI. I think this is a crucial point of your experience and should be discussed.

A: We see a value for the preselection of patients presenting with elevated serum PSA who will have to undergo mpMRI and biopsy. Prospective studies to test the PGI in a setting including mpMRI are requested to address this marker application. Lines 182 – 187: “In the current clinical setting for biopsy decision the ability of the PSA glycoprofile to identify significant cancer could improve accuracy of preselection of men who have to undergo expensive imaging and subsequent biopsy, thus reducing costs and the number of negative biopsies without loss of significant tumour cases. The results presented here encourage prospective studies to test positioning of the PGI prior to mpMRI in prostate biopsy decision making.”

 

-What about cost of PGI?

A: The cost of PGI test is not yet determined and it will be done in the future by a discussion with experts.

 

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Thank you for the changes made to the manuscript. Congratulations for this interesting study