In this study, we assessed the usefulness of early PSA change after ADT administration as a predictive marker for mHSPC patients treated with ADT. We found that a PSA ≥ 1% after 3 months of ADT was a strong predictive factor of OS. In addition, a Gleason score of 8 or more, an EOD ≥ 2, and a PSA ≥ 1% after 3 months of ADT were significantly associated with shorter time to CRPC.
In previous studies, serum bone markers (15), circulating tumor cells (CTC), (16) and single nucleotide polymorphisms (17) were identified as potential prognostic markers for patients with mHSPC who were administered ADT treatments. Goodman et al. assessed the prognostic factors in 33 mHSPC patients treated with ADT and found that initial CTC values predict the duration and magnitude of response to hormonal therapy. CTC enumeration may identify patients at risk of progression to CRPC before initiation of androgen deprivation therapy (16).
Conversely, other reports focus on the PSA value. PSA-related variables, including initial PSA levels and PSA kinetics, have been the most frequently assessed biomarkers in mHSPC (18). Among the PSA kinetic variables, PSA nadir and time to PSA nadir are promising biomarkers for mHSPC (19, 20). However, previous studies reported that the median time to PSA nadir was 6–10 months (19, 20), which means that the prognosis was predictable more than half a year after the initiation of ADT. Guangiie et al. reported that a PSA velocity’s decline of > 11 ng/mL per month was significantly associated with an increased risk of progression to CRPC after initial ADT (21). Although further studies are needed to identify the best marker among PSA-related variables to predict the outcome of mHSPC patients, PSA change at 3 months is a simple and convenient indicator for the prediction of clinical outcomes. Sato et al. (22) also reported that in the study of ADT for mHSPC, the group with a PSA decreased by 98.5% at 12 weeks after the initiation of treatment had significantly increased PSA progression-free survival and OS. In our study, a PSA ≥ 1% after 3 months of ADT was an independent predictive marker. In their report, patients with visceral metastases were relatively low at 3.3%. On the other hand, in our report, 24% of patients had visceral metastases, which have relatively poor prognoses. It is very interesting to note that, even in such patients, an early PSA decline contributed to significant prolongation of OS. It is suggested that the group with a significant decrease in PSA in the early stage of treatment may have a better prognosis.
The independent factors affecting the time to CRPC in our study were: I) a Gleason score of 8 or more, II) an EOD ≥ 2, and III) PSA ≥ 1% after 3 months of ADT. In the LATITUDE trial (6), visceral metastasis was listed as an item of high risk, but in our study, visceral metastasis was not an independent predictor of poor prognosis. Distant metastasis, particularly visceral metastasis, represents an important negative prognostic factor in prostate cancers (3, 23–26). Peng-Fei et al. investigated the OS of 1358 prostate cancer patients with visceral metastasis and reported that lung metastasis had a better prognosis than brain or liver metastasis (27). In our study, 11 out of 17 patients (65%) with visceral metastasis only had lung metastasis. This might be one of the reasons that visceral metastasis was not shown to be a high-risk factor in our study.
The present study reported that the group with PSA ≥ 1% after 3 months of ADT had a poor prognosis. Based on this result, PSA ≥ 1% after 3 months of ADT may become one of the high-risk factors in mHSPC. However, there are no prospective reports observing a decline in PSA levels in the early stage. Nevertheless, more cases and prospective studies are required in the future for conclusive evidence.
A limitation of the present study is that it is a retrospective analysis performed at two hospitals. As such, the number of cases is small, and there is a possibility that patient and treatment selections might have been biased. In addition, the judgment of the attending physician is adopted as one of the definitions of CRPC, and there is a possibility of the data being affected by the difference in judgments of the attending physicians. However, this study points out the possibility that PSA ≥ 1% after 3 months of ADT correlates with a poor prognosis, which has significant importance.