Several authors have addressed the role of HE4 during treatment and follow-up. The preoperative level of HE4 has been advocated to be a predictor of the possibility of performing radical debulking surgery with reported cut-off values varying between 154 - 262 pmol/L [7, 10, 13, 14]. A preoperative level of HE4 above a median level of 394 pmol/L has been reported to be significantly associated with progression and mortality [15]. We could not corroborate these results as we found no significant differences in preoperative levels of neither HE4 nor CA125 in the group that was radically debulked compared to the group left with macroscopic disease. Our lack of corroboration could partly be due to limitations in our sample size with only a small number of patients with both pre- and postoperative tumor markers samples.
The result of the surgical intervention is assessed by the surgeon at the end of operation and currently there are no objective variables indicating radicality. It is therefore interesting to note that we found significantly lower median levels of HE4 and CA125 in patients where complete cytoreduction was achieved compared to the group left with minimal or bulky disease. Although CA125 also decreased after a successful cytoreduction, a majority of these patients still had elevated CA125 values. The levels of CA125 may be elevated postoperatively due to a peritoneal reaction after the surgical procedure. Hence, a postoperative elevation of CA125 has to be considered in relation to the time between surgery and blood sampling as well as the clinical condition of the patient. The median time from surgery to start of chemotherapy in our study was 42 days (range 13–92). It would therefore seem reasonable to conclude that surgical trauma has no impact on the CA125 levels prior to start of chemotherapy. However, as HE4 is reported to be independent of peritoneal reactions [16], and as the half time clearance is less than 4 hours [17], we would like to postulate that a normalized HE4 value postoperatively is a promising marker to evaluate the result of surgery and merits further investigation.
Chemotherapy, PFS and OS
The role of HE4 in monitoring chemotherapy has been evaluated regarding prognosis and prediction of platinum resistance. The serum levels of HE4 were under URL in 86% of patients reported as optimally tumor reduced. The median levels of HE4 in patients with normal values at the start of chemotherapy remained below URL during treatment whereas elevated HE4 levels at start of treatment decreased significantly. A similar result was seen for CA125 (Fig.5). Based on our data, we suggest that HE4 and CA125 are valid markers to monitor the response to chemotherapy, but only when the markers are above the normal range prior to start of chemotherapy. As a majority of patients (68 %) had elevated CA125 levels when treatment was started and only 42% had elevated HE4 levels, the role of CA125 as the most important marker for monitoring chemotherapy is thereby further confirmed and in line with Ferraro [18].
We found significantly prolonged PFS and OS in patients with HE4 levels under URL 82 pmol/L at the start of chemotherapy. Further, PFS was significantly shorter even when HE4 values were above the URL at start of chemotherapy but dropped to normal range after three and six cycles of chemotherapy. These results are in concordance with Steffensen et al. [6] who found a significant shorter PFS in 139 patients with high levels of HE4 just before start of chemotherapy. Also Kong et al. [9] described that the pretreatment HE4 level was a predictor of prognosis. On the other hand, in our study the level of CA125 was not predictive of either PFS or OS. Our results are in contrast to Rocconi et al. [19], who showed that both PFS and OS were significantly longer if CA125 was normalized after three cycles of chemotherapy regardless of the initial value.
Relapse and Platinum resistance
It is well known that the majority of patients treated for advanced EOC will have a relapse within few years after end of treatment. Definition of recurrence in the case of CA125 is as defined by the Gynecologic Cancer Intergroup [20].
The question about monitoring CA125 levels after adjuvant treatment for EOS in patients in complete remission has been intensively debated [21, 22, 23, 24]. Diagnosis of recurrent disease is often preceded by an increase of CA125, roughly two to six months before clinical symptoms, raising the possibility of starting chemotherapy based solely on increasing CA125 levels.
Rustin et al. [22] demonstrated no improved survival but decreased quality of life in a group with early re-treatment compared to a group with start of treatment first after subjective symptoms. His study has been subject to criticism as the re-treatment regimens were very diverse and no patient underwent surgical intervention. On the other hand Fleming et al. [25] showed that delayed re-treatment, after an obvious increase in CA125 levels, decreased the possibility of achieving optimal tumor resection by a second surgical effort. To monitor and react on a rise in tumor markers could be further advocated by the DESKTOP III study that concluded that surgery in a situation of relapse affected prognosis but only when complete resection of all macroscopic tumor lesions could be attained and only in platinum-sensitive patients [26].
Reports concerning the role of HE4 during follow-up have suggested that HE4 is a more sensitive marker for diagnosis of recurrent EOC than CA125 [27, 28]. Most of these studies are small, but Steffensen et al. [11] demonstrated in a material of 88 patients that HE4 is a highly sensitive marker for relapsed disease. Anastasi et al. [29] observed an earlier increase of HE4 than CA125 in a very small group of eight patients with recurrence. In our material 21 recurrences were observed during the observation time of up to 68 months. Unfortunately, we did not succeed in obtaining samples from all planned visits as many dropped out due to practical difficulties. Despite this we can still conclude that both HE4 or CA125 alone or even better both together, indicate a recurrence with elevations occurring most often in parallel, roughly three to four months before confirmed recurrence (Fig. 5). Further research is needed to address the implications of increasing tumor markers.
It has been suggested that HE4 levels are a predictor of platinum resistance [30, 31].
Due to limited number of patients we have not investigated the role of HE4 in predicting the possibility of performing complete tumor resection after NACT. This is important for prognosis as a surgical intervention without complete tumor resection is of no benefit for the patient and in addition the interval to next chemotherapy might be prolonged. HE4 has been described as a useful tool in this question [27, 32].
In summary we can conclude that the levels of tumor markers at start of chemotherapy seem to be the most important factors for PFS and OS and also a predictor of platinum resistance. HE4 does not signal a recurrence earlier than CA125. We find the role of HE4 after surgical intervention to be of importance and suggest future studies of HE4 levels before and shortly after primary surgery for an objective evaluation of the surgical outcome and thereby also as a predictor of prognosis.