SBOT-MP was described nearly 10 years ago. Few specific papers have been devoted to the study of the prognosis of patients with such tumors and many questions remain unanswered about this disease. Different reports suggest that the prognosis for patients with early-stage disease (without peritoneal implants) seems to be similar in SBOTs with and without an MP pattern [3
]. Nevertheless, this entity is considered as having a higher risk for extraovarian disease. Interest in complete peritoneal staging surgery is currently debated in BOTs but, given the higher rate of extraovarian disease from lesions displaying an MP pattern, the use of complete staging surgery remains the rule in MP disease [12
]. Very few series have specifically been devoted to evaluating the survival of patients with SBOT-MP and peritoneal implants. Those that have are summarized in . The present study includes the largest number of patients with stage II and stage III SBOT-MP (). Several papers describing the clinical behavior of SBOT-MP claimed that these tumors have a higher rate of invasive implants than with typical SBOT [3
]. These rates were similar in our study (16% versus 10%; p
= .3). Other series have reported similar findings. In a study by Slomovitz et al. [10
], including six patients with stage II/III SBOT-MP, none of them had invasive implants. In a series by Deavers et al. [5
], the difference in the percentages of patients with invasive implants did not reach statistical significance (three of 18 [18%] SBOT-MP patients versus five of 81 [6%] typical SBOT patients). One explanation for such results in the study by Deavers et al. [5
], as well as in ours, is that the rates were different but failed to reach statistical significance because the number of patients was too small. Nevertheless, in other series in which the type of implant (invasive versus noninvasive) had a significant prognostic value, the number of patients studied was smaller than in ours. Another explanation is perhaps that, finally, no statistical difference can be demonstrated between SBOT-MP and typical SBOT in terms of the type of implant. In contrast, the rate of invasive implants was lower in the SBOT-MP group (8% [one of 13 patients] versus 17% [four of 24 patients]) in the series reported by Prat and de Nictolis [13
Literature review of series reporting advanced-stage serous borderline tumor of the ovary with a micropapillary pattern (only patients followed up were reported)
In our study, two characteristics were statistically different between the two groups. The first concerned disease extension, which seemed to be greater in the SBOT-MP group—the percentage of patients with more than three different involved peritoneal sites was significantly higher and the rate of stage III disease (versus stage II) was also higher and almost of borderline statistical significance in the SBOT-MP group. Nevertheless, although this difference could have a potential impact on prognosis, the overall survival and recurrence-free survival times were similar in the two groups of patients.
This is a major point because it suggests that the overall prognosis for patients with SBOT, with or without a MP pattern, may be similar. It is essential to review the literature regarding this question because the crucial question behind the description of a new pathological entity is whether this new lesion will exert a different impact on survival (and, if so, whether it should be treated in a different way). Having examined different series that reported on SBOT-MP with peritoneal implants, we found two different “groups” of papers in terms of prognosis (). In three series that (taken together) reported on 71 patients, 21 deaths or persistent/progressive disease were observed [4
]. In the series reported by Smith Sehdev et al. [6
], among 12 patients with persistent/progressive disease, 11 initially had invasive implants. Similarly, in the series by Longacre et al. [4
], three of four patients who died as a result of the disease also had invasive implants. Such poor results would logically lead to a modification of the current classification of serous tumors of the ovary, as suggested by Kurman et al. [14
]. In his new classification, SBOT-MP is considered as a “non-invasive micropapillary (or intraepithelial) low-grade serous carcinoma,” an intermediate form between an atypical serous tumor (typical SBOT for other authors) and low-grade carcinoma, so-called “invasive micropapillary serous carcinoma” (which exhibits stromal infiltration). Recent molecular genetic studies (particularly BRAF
mutations) provide cogent evidence to support this new classification. Such a classification is logical if the prognosis for patients with SBOT-MP is considered to be clearly different from that of patients with non-MP forms.
On the other hand, five other series published—reporting, respectively, six, 12 (in two series), 15 and 53 cases with follow-up—reported an overall “good” prognosis in SBOT-MP patients. Of a total of 98 cases reported in those different publications, only nine deaths or persistent/progressive disease were reported [3
]. It is interesting to note that, in three of these series, patients with persistent/progressive disease or who had died initially had invasive implants. Such was the case for both deaths in the series reported by Eichhorn et al. [3
] and the only death in the series reported by Prat et al. [13
] and Gilks et al. [3
]. In our series, among the nine patients with invasive implants during initial management in the SBOT-MP group, only one relapsed in the form of noninvasive disease and is currently disease free. In the present series, the 5-year rates of recurrent invasive disease in the SBOT-MP and typical SBOT groups were, respectively, 18% and 4%. This difference was not statistically significant, perhaps because the number of patients with invasive disease was too small throughout the series. Nevertheless, this (nonsignificant) difference had no effect on survival.
How can one explain such differences among the results in the literature? The first explanation concerns the histological interpretation of an MP pattern. It is not always easy to characterize SBOT in terms of the pathological analysis. Nonetheless, the results in were reported by experienced teams in expert centers who were well-versed in the histological analysis of ovarian tumors in their country. This is therefore unlikely to be the explanation. As pointed out by Prat [16
], a plausible explanation for such differences is the way in which the analyzed cases were recruited in these different series. Some of the published series were obtained from consultation or referral material (inevitably increasing the rate of patients with “ambiguous lesions” akin to carcinoma, i.e., patients with invasive implants). Other series were based on the analysis of records of cases treated in a single institution [16
Another potential explanation is the follow-up duration. Two recent series highlighted the time dependence of the recurrence rate in SBOT [4
]. Recurrences are not uncommon after 5 years for patients with this tumor [4
]. Nevertheless, the duration of follow-up reported in the current series is similar to, or longer than, that of other series that reported a clear difference in terms of prognosis between SBOT-MP and typical SBOT patients ().
The only factor identified as a risk factor for recurrence in the SBOT-MP group in this series was the use of conservative surgery (). However, the rate of conservative treatment was lower in the SBOT-MP group than in their typical SBOT counterparts. Less recourse to conservative surgery in the SBOT-MP group could have been a result of the fact that, in most published series on SBOT-MP (including early- and advanced-stage disease), the tumors were more frequently bilateral than in typical SBOT [3
]. If tumors with an MP pattern are more frequently bilateral, the use of conservative surgery decreases. In our review of the literature concerning the conservative management of SBOT-MP patients, only one series was published by our group on this topic (15 cases including early- and advanced-stage disease). New cases of advanced-stage disease have since been included in the current series. In other series, conservative treatments were described in case reports and were more frequently used in early-stage disease [18
]. These different data (concerning a few cases) suggest that conservative surgery could be safely proposed, at least for early-stage SBOT-MP patients, but a high rate of recurrence is expected [18
]. Among the eight patients treated conservatively in the current series, five relapsed, three in the form of noninvasive disease and two in the form of invasive carcinoma at least on the remaining ovary. One of these latter patients died as a result of the disease. Here, we have probably reached one of the limits of conservative surgery in borderline ovarian disease. In patients with SBOT-MP and peritoneal implants, the results of conservative surgery (five of eight patients relapsed, two of them in the form of invasive carcinoma, and one of them succumbed to the disease) were not good, and suggest that, in cases of bilateral ovarian involvement during initial management, bilateral salpingo-oophorectomy should be preferred to conservative surgery in such patients.
In the present series, the rates of invasive implants were similar in patients with an SBOT with peritoneal implants, with and without an MP pattern. The presence of an MP pattern does not appear to portend a worse prognosis than in patients whose tumor is devoid of this feature. The only prognostic factor for recurrence in such patients was the use of conservative surgery. Further studies are needed to evaluate the results of conservative surgery in this context and to evaluate the prognosis of patients with an MP pattern.