The survival period of patients with MPC remains very short because this disease is resistant to chemotherapy and progresses rapidly. The sequencing of therapeutic options in the second-line setting for patients with MPC remains a significant unfulfilled need. We examined the outcomes of second-line treatment using the cohort of patients who received FFX or GnP as a first-line therapy. First, we conducted a study that focused on comparing survival with chemotherapy versus BSC. Second, we compared survival following second-line combination chemotherapy or mono chemotherapy.
Most prior randomized control trials (RCT) did not compare active treatment with BSC. The first and only phase III RCT compared BSC to oxaliplatin, fluoropyrimidine (5-FU), and folic acid (FA) (OFF regimen) in 46 patients [9]. Although this study ended prematurely due to low enrollment, the OFF regimen was associated with significantly higher survival after second-line treatment compared with BSC (4.8 versus 2.3 months, p = 0.008).
In our study, 77 patients received BSC after FFX and GnP failed. There is no data comparing chemotherapy to BSC in the second-line treatment setting after refractory response to intensive chemotherapy regimens such as FFX and GnP. Survival of the second-line chemotherapy group was considerably longer than the BSC’s (mOS 5.2 versus 2.7 months, HR:0.42 (95% CI: 0.31–0.57), P < 0.01). However, because these two groups may differ in terms of background factors after first-line treatment failure, a propensity score-adjustment analysis was performed before second-line treatment by selecting clinically meaningful variables. The adjusted results also revealed a statistically significant increase in mOS for patients receiving second-line chemotherapy versus those that chose the second-line BSC group (mOS 5.2 versus 2.6 months, HR:0.38 (95% CI: 0.27–0.54), P < 0.01). These findings suggest that administering any second-line chemotherapy to patients who are considered chemotherapy tolerant will help to prolong survival.
As a criterion for selecting a regimen for second-line treatment, we confirmed the correlation between the adverse events that occurred during first-line treatment (Table 3). Analysis 1 showed that the BSC group had a higher incidence of grade 3 or higher anemia than did the second-line chemotherapy group (P = 0.04). In contrast, no differences in the frequency of neutropenia, febrile neutropenia, or gastrointestinal toxicity were observed between the groups, all of which had no impact on the transition to second-line treatment or BSC. Reports have shown that anemia is associated with chemotherapy resistance, with our study showing a similar trend [10]. For cases with grade 3 or higher anemia, depending on the situation after first-line treatment failure, BSC may be considered as a necessary option. In Analysis 2, no differences in adverse events occurring during first-line treatment were observed between the combination and monotherapy groups. For patients who exhibited severe peripheral neuropathy during first-line treatment, avoiding regimens that may cause peripheral neuropathy during second-line treatment may not decrease their QOL.
Patient background data for Analysis 1 showed that the BSC group had a higher proportion of patients with a history of resection than did the chemotherapy group. We believe that there are two reasons for such a finding. The first reason for this is that in Japan, S-1, a fluoropyrimidine-based agent, is the standard of care for adjuvant chemotherapy, whereas gemcitabine-based regimens are selected for recurrence. When this regimen becomes ineffective, treatment options are limited and BSC may be considered. The second reason is that this study used a database from a period wherein the safety of FFX in second-line therapy was not well established. Therefore, FFX may have been less commonly selected among patients refractory to gemcitabine-based regimen.
The validity of second-line therapy for recurrent cases after surgery remains controversial. However, given that it is being carried out in clinical practice, we conducted an adjusted analysis. Regarding the validity of chemotherapy for postoperative cases, we are currently conducting a prospective investigation on the matter (NAPOLEON2 study).
In recurrent or advanced pancreatic cancer, the prognostic difference based on the background cannot be ignored. In a sub-analysis of the main study, survival data for metastatic PC (mPC) and recurrent (rPC) treated with FFX or GnP therapy as first-line treatment were analyzed, with our findings showing that rPC had a favorable prognosis. However, propensity score-matched analysis revealed no difference in prognosis between the two groups with chemotherapy [11]. However, the possibility that mPC and rPC contribute to prognosis cannot be ruled out in second-line treatment; hence, additional prognostic analyses were conducted. Notably, Analysis 1 showed no significant difference between the two groups, with mPC (n = 196) and rPC (n = 37) at 4.0 and 4.9 months, respectively (HR 0.78; 95% CI, 0.52–1.16; P = 0.21). Similarly, Analysis 2 showed no significant difference between the two groups, with mPC (n = 137) and rPC (n = 19) at 5.1 and 8.9 months, respectively (HR 0.65; 95% CI, 0.36–1.15; P = 0.14). In both Analysis 1 and Analysis 2, no significant differences were observed between the two groups.
Although nal-IRI and 5-FU/FA combination therapy is recommended for second-line treatment after a gemcitabine-based regimen fails, data regarding the efficacy of other combination regimens are lacking. A few pivotal phase III trials have been conducted. In a phase III RCT, the OFF regimen significantly improved survival in patients with gemcitabine refractory pancreatic cancer compared with a 5-FU/FA regimen; the benefit of additional oxaliplatin was also demonstrated (mOS 5.9 versus 3.3 months, p = 0.01, median time to progression 2.9 versus 2.0 months, p = 0.019) [12]. On the other hand, FOLFOX has been observed to be subordinate to 5-FU/FA for OS (median 6.1 versus 9.9 months, p = 0.02), but no difference was observed in PFS (median, 3.1 versus 2.9 months, p = 0.02) [16]; thus, leaving the significance of oxaliplatin in second-line therapy unclear. The NAPOLI-1 study, a pivotal phase III RCT, found that nal-IRI plus 5-FU/FA significantly improved survival compared with 5-FU/FA (median: 6.1 versus 4.2 months, p = 0.0012) and PFS (median, 3.1 versus 1.5 months, p = 0.00001) in patients previously treated with a gemcitabine-based regimen [13]. The mOS and mPFS in various phase III RCTs of second-line pancreatic cancer treatment is inconsistent, ranging from about 3.3 to 9.9 months and 1.5 to 3.1 months [9, 12, 13, 16]. Most studies to date have evaluated second-line regimens following gemcitabine-based therapy failure. Furthermore, there is little evidence supporting the choice between combination chemotherapy or mono chemotherapy for patients who are refractory to FFX or GnP treatment.
We compared the survival of the second-line combination chemotherapy group with the second-line mono chemotherapy group. Remarkably, the combination chemotherapy group did not exert substantial variations in OS (median 5.5 versus 4.4 months, p = 0.48) or PFS (median 3.0 versus 2.5 months, p = 0.49) as compared to the mono chemotherapy group. Propensity score-adjustment analysis did exert significant differences in OS (median 5.5 versus 4.8 months, p = 0.53) or PFS (median 2.6 versus 3.0 months, p = 0.92). Significant differences in patients’ backgrounds between the two groups were reported in age, ECOG-PS, and LDH. Patients in the mono chemotherapy group were inclined to be older and had lower ECOG-PS. Although second-line chemotherapy for MPC is expected to prolong survival, increasing the intensity may not necessarily result in increased longevity. Patients with MPC who have exerted poor response to first-line chemotherapy frequently present with poor ECOG-PS and a high symptom burden; thus, a combination chemotherapeutic approach may not be appropriate for patients in the salvage setting. Patients with a poor response, worsened ECOG-PS, and a high tumor burden is unlikely to benefit from intensive chemotherapy, and they may suffer more harm than benefit [17].
In the current study, the survival period in patients receiving combination chemotherapy was comparable to that of patients receiving mono chemotherapy; however, there were some limitations. First, while we performed a propensity score-adjustment analysis, this is a retrospective study, which requires consideration of selection bias in treatment decisions. Second, we have not investigated the role of the induction dose of the second-line regimens, the response rate, or adverse events that may have influenced the choice of mono chemotherapy or combination chemotherapy as the second-line regimen. Third, this study did not include a nal-IRI-based regimen as a second-line treatment, because it was not endorsed for use in Japan during the survey period. The NAPOLEON-2 is a prospective trial currently ongoing, which seeks to investigate the efficacy of combination chemotherapy (nal-IRI plus 5-FU/FA) as compared to mono chemotherapy (S-1); the results are currently awaited (UMIN000043939).
Conclusively, after comparing chemotherapy versus BSC, if the patient’s tolerability is tolerable, second-line chemotherapy for patients with MPC can be expected to prolong survival. Regarding the treatment options, combination chemotherapy does not always contribute to longer survival and that mono chemotherapy should also be considered a viable option.