Clinical significance of germline breast cancer susceptibility gene (gBRCA) testing and olaparib as maintenance therapy for patients with pancreatic cancer

Background Germline breast cancer susceptibility gene (gBRCA) mutation in patients with pancreatic cancer (PC) is not common in clinical practice. Therefore, factors that efficiently show gBRCA mutations and the real-world outcomes of olaparib maintenance therapy have not been fully established. In the present study, we clarified the indicators for the effective detection of gBRCA mutation and the efficacy and safety of olaparib as maintenance therapy. Methods We retrospectively analyzed 84 patients with PC who underwent gBRCA testing (BRACAnalysis, Myriad Genetics, Salt Lake City, UT, USA) at our institute between January 2021 and March 2022. For each patient, clinical data were extracted from medical records. Results The median patient age was 64 y (29–85 y), and 41 patients (48.8%) were male. The gBRCA mutations were identified in 10 (11.9%) patients; two patients had BRCA1 mutation and eight had BRCA2 mutation. All patients with gBRCA mutation had a family history of any cancer, and eight of them had a family history of Hereditary Breast and Ovarian Cancer syndrome (HBOC)-related cancer. The gBRCA mutation rate was higher for patients with PC with a family history of HBOC-related cancer compared to that in patients with PC having a family history of other cancers and no family history of cancer (22.9% vs. 4.1%; P = 0.014). In our study, eight out of 10 patients with gBRCA-positive PC received olaparib after platinum-based chemotherapy. The best responses to platinum-based chemotherapy included a complete response in one patient (12.5%) and a partial response in seven patients (87.5%). The median duration of treatment with platinum-based chemotherapy plus olaparib was 17.5 months (8–87 months), and the duration of treatment with olaparib maintenance therapy was 11 months (1–30 months). During olaparib maintenance therapy, three patients showed no disease progression. One of these three patients underwent conversion surgery after receiving olaparib for 12 months. Conclusions The gBRCA testing should be considered proactively, especially in patients with PC with a family history of HBOC-related cancer.


Background
Pancreatic cancer (PC) has the worst prognosis of all solid cancers [1].Both the incidence and mortality of PC are increasing worldwide, including in the United States, Europe, and Japan, making it the third-most prevalent cause of cancer-related death in the United States [2].Development of further treatment modalities is needed to improve prognosis [3][4][5].PC has familial accumulation, and familial PC, defined as having two or more first-degree relatives (parents, siblings, or children) with PC, has been proposed [6].There is increasing evidence for the genomic analysis of PC [7][8][9][10].Germline pathological variants, such as ATM, BRCA1, BRCA2, CHEK2, and PALB2, which are known to cause homologous recombination deficiency (HRD), have been reported to be present in 10-20% of patients with PC [11][12][13].Germline BRCA1/2 (gBRCA) mutation is found in 4-7% of PC patients, occurring more frequently than other genes associated with HRD, such as ATM, CHEK2, and PALB2 [14][15][16][17][18][19].BRCA1/2 encodes a tumor suppressor protein involved in the repair of double-stranded DNA breaks caused by homologous recombination defects [20,21].Mutations in gBRCA are associated with the risk of developing breast, ovarian, prostate, and pancreatic cancers [17,22,23].Germline BRCA mutation, currently examined using BRACAnalysis (Myriad Genetics, Salt Lake City, UT, USA) in Japan, is principally implicated in Hereditary Breast and Ovarian Cancer syndrome (HBOC) [24,25].Once diagnosed with HBOC, regular screening for HBOC-related cancers can lead to early detection and treatment; risk-reducing surgeries are considered to be important treatment options [26][27][28].
The search for gBRCA as a biomarker for PC therapy is important in clinical practice.The prognosis of patients with gBRCA-positive PC is favorable, with 67.4-76.3% of these patients responding well to platinum-based chemotherapy [29,30].This is because gBRCA-mutant tumor cells assume that double-stranded DNA damage caused by platinum-based regimens could not be repaired due to HRD [31,32].The POLO study in 2019 investigated the efficacy of olaparib, a poly-ADP ribose polymerase (PARP) inhibitor, as maintenance therapy and indicated an improvement in median progression-free survival with olaparib maintenance therapy after platinum-based chemotherapy (7.4 months in the olaparib group vs. 3.8 months in the placebo group; hazard ratio for disease progression or death, 0.53; 95% confidence interval, 0.35-0.82;P = 0.004) [33].Based on these results, olaparib as maintenance chemotherapy after platinum-based chemotherapy for patients with gBRCA-positive unresectable PC was covered by insurance in Japan in December 2020.BRACAnalysis was also approved by national insurance in Japan as a companion diagnostic test for PARP inhibitors in patients with PC [24].The frequency of gBRCA mutation in patients with PC is uncommon in clinical practice.Hence, the factors that were associated with gBRCA mutation and the real-world outcomes of olaparib maintenance therapy have not been fully elucidated.The current study examined the indicators for the detection of gBRCA mutation and the efficacy and safety of olaparib maintenance therapy.

Patient identification and data collection
We conducted a retrospective, observational study of 84 patients with PC who underwent germline BRCA1/2 genetic testing (BRACAnalysis) in a Japanese cancer referral center (Osaka International Cancer Institute) between January 2021 and March 2022.For each patient, clinical data were extracted from medical records.Follow-up data from the patients were censored on August 31, 2023.The following clinical parameters were obtained: age, sex, histological diagnosis, resectability (disease status) at the initiation of treatment for PC, and family history of any cancer.Resectability was discussed by the Cancer Board of our facility before initiating treatment and was classified as resectable (R), borderlineresectable (BR), locally-advanced unresectable (UR-LA), metastatic unresectable (UR-M), and postoperative recurrence according to the National Comprehensive Cancer Network guidelines [34].The submission for BRACAnalysis was at the discretion of the physicians and the results were shown as either BRCA1 or BRCA2 mutations, variants of unknown significance, or no mutation.
Olaparib was used as maintenance therapy for patients without disease progression after platinum-based chemotherapy (≥ 16 weeks).Tumor responses were graded according to the Response Evaluation Criteria in Solid Tumor (RECIST) ver.1.1 [35].Treatment outcomes with olaparib as maintenance therapy were evaluated for the duration of olaparib treatment and the occurrence of adverse events (AEs).AEs were graded according to the National Cancer Institute Common Terminology Criteria for Adverse Events, version 5.0.
This study was conducted in accordance with the Declaration of Helsinki.Ethical approval was obtained from the Ethical Review Committee of the Osaka International Cancer Institute (20148-3).The requirement for informed consent was waived by the opt-out method of our hospital's website.

Statistical analysis
The relation between gBRCA mutation and family history was assessed using Fisher's exact test.The duration of platinum-based chemotherapy plus olaparib and the duration of olaparib maintenance therapy were compared using Student's t-test.Differences were considered statistically significant if P values were < 0.05.Statistical analysis was performed using EZR (Saitama Medical Center, Jichi Medical University, Saitama, Japan), a graphical interface for R, and the R Commander software package for Mac (version 1.61; R Foundation for Statistical Computing, Vienna, Austria) [36].

Patient characteristics
The patient characteristics are summarized in

Results of gBRCA testing
The results of gBRCA testing (BRACAnalysis) are summarized in Table 2.The timing of undergoing gBRCA testing was: 12 patients (14.3%) underwent gBRCA testing before the initiation of chemotherapy, 50 patients (59.5%) during first line treatment, 18 patients (21.4%) during second line treatment, and four patients (4.8%) after third line treatment.Germline BRCA mutation was identified in 10 patients (11.9%).Two of them had germline BRCA1 mutation and eight had germline BRCA2 mutation.All patients with gBRCA-positive PC had a family history of any cancer, and eight of them had a family history of HBOC-related cancer.The gBRCA mutation rate was higher for patients with PC with a family history

Treatment outcomes in patients with gBRCA-positive PC
In this study, all ten patients with gBRCA-positive PC received platinum-based chemotherapy.Among them, eight patients switched to olaparib maintenance therapy, one patient experienced tumor progression before switching to olaparib, and one underwent conversion surgery due to excellent response to FOLFIRINOX.The treatment outcomes of patients who underwent platinum-based chemotherapy and olaparib maintenance therapy are shown in Table 3.The number of chemotherapeutic regimens before initiating platinum-based chemotherapy was zero in five patients (62.5%), one in two patients (25.0%), and two in one patient (12.5%).The median duration of platinum-based chemotherapy was 9 months (4-57 months).Of the eight patients who underwent olaparib maintenance therapy, the best responses to platinum-based chemotherapy included a complete response in one patient (12.5%) and a partial response in seven patients (87.5%).The median duration of treatment with platinum-based chemotherapy plus olaparib was 17.5 months (8-87 months), and the duration of treatment with olaparib maintenance therapy was 11 months (1-30 months).Between five patients who underwent BRACAnalysis at an earlier timing (before the initiation of chemotherapy and during first line) and three patients at a later timing (during second line or later), there was no significant difference between the duration of platinum-based chemotherapy plus olaparib (median (range); 14 months (8-37 months) vs. 28 months (15-87 months); P = 0.49), and the duration of olaparib maintenance therapy (median (range); 9 months (1-30 months) vs. 12 months (10-12 months); P = 0.46).
During olaparib maintenance therapy, five out of eight patients were judged to have progressive disease, leading to the discontinuation of olaparib.Four of these five patients subsequently underwent different chemotherapeutic regimens, while the other patient chose not to continue further chemotherapy due to advanced age.The remaining three of the eight patients were free from disease progression.One of these three patients underwent conversion surgery after receiving olaparib for 12 months and the other two patients continued to receive olaparib at the end of follow-up.
The AEs during the entire period of olaparib maintenance therapy are shown in Table 4.The most common AEs (all grades) were fatigue, nausea, and anemia.Grade 3 or higher AEs were anemia and thrombocytopenia in one patient, and AEs were managed by dose modification.
The frequency of the gBRCA mutation and gBRCApositive rates in the current study were higher than that in previous reports.The selection of patients for gBRCA testing was done at the discretion of each physician, which may have strongly influenced the high positive rate.Furthermore, gBRCA mutation was detected in 22.9% of patients with PC with a family history of HBOC-related cancer, compared to only 4.1% of patients with PC with no family history of HBOC-related cancer.
A family history of any cancer has been reported in 94.4% of patients with gBRCA-positive PC, of which 79.6% had a family history of HBOC-related cancer [37].A substantial difference in the frequency of a family history of HBOC-related cancer has been clarified between patient groups with gBRCA mutation-positive and -negative PC [19].Taken together with these previous results, a family history of HBOC-related cancer could be an indicator for the detection of gBRCA mutation.Since approximately 4% of patients without a family history of HBOC-related cancer were gBRCA-positive, gBRCA testing should also be considered for these patients as well.
The timing for undergoing gBRCA testing in this study (before the initiation of chemotherapy, 14.3%; during first line chemotherapy, 59.5%) was earlier than that in a previous report (before the initiation of chemotherapy, 17.6%; during first line chemotherapy, 36.8%)[19].The results of gBRCA testing could play an important role in the selection of a second-line chemotherapeutic regimen because platinum-based chemotherapy, such as FOLFIRINOX, is preferred because it shows favorable treatment outcomes in patients with gBRCA-positive PC [38][39][40][41].This preference may influence physicians' decisions regarding the timing of gBRCA testing.Early submission of gBRCA testing before the end of first-line chemotherapy is considered important, especially when gemcitabine and nab-paclitaxel combination therapy is chosen as the first-line chemotherapy.
In the current study, the median duration of olaparib maintenance therapy was 11 months, including the case in which conversion surgery was performed.Longterm combination chemotherapy for patients with unresectable PC has been reported to endorse eligibility for conversion surgery [42][43][44].In a study of patients with unresectable PC treated with combination chemotherapy, chemotherapy for > 8 months was reported to be an independent prognostic factor [45].Therefore, long-term continuation of chemotherapy with tolerable toxicity is important for patients with unresectable PC.However, long-term administration of FOLFIRINOX can cause various AEs, including chemotherapy-induced peripheral neuropathy (CIPN), which is primarily caused by oxaliplatin [46][47][48].Severe CIPN can affect the continuation of chemotherapy and patient prognosis [49].Olaparib maintenance therapy can be a useful treatment option with manageable toxicity, especially in patients with severe CIPN [50].Recently, Stossel et al. reported that patients with gBRCA-positive PC had a favorable response to platinum-based chemotherapy and PARP inhibitors, but most patients experienced resistance [51].Homologous recombination proficiency and secondary mutations restoring partial functionality have been identified as the dominant mechanisms of resistance.Further research is required to address the treatment strategies for patients who develop resistance.
This study had some limitations.First, this was a singlecenter, retrospective, observational study.Second, the selection of patients for whom gBRCA testing was performed, the timing of gBRCA testing, and the timing of transition to olaparib maintenance therapy in patients with gBRCA-positive PC were at the discretion of each physician.The limited number of patients may have introduced selection bias.

Conclusion
In our single-center, retrospective study, gBRCA mutation was particularly high in patients with PC with a family history of HBOC-related cancer.Platinum-based chemotherapy and olaparib maintenance therapy for patients with gBRCA-positive PC can be expected to prolong the prognosis; therefore, gBRCA testing should be considered proactively, especially for patients with PC with a family history of HBOC-related cancer.

Table 1
Characteristics of 84 patients with pancreatic cancer (PC) who underwent gBRCA testing (BRACAnalysis) at the Osaka International Cancer Institute between January 2021 and March 2022 BR, borderline-resectable; UR-LA, locally-advanced unresectable; UR-M, metastatic unresectable; HBOC, hereditary breast and ovarian cancer syndrome

Table 2
Results of gBRCA testing * Fisher's exact test BRCA, breast cancer susceptibility gene; HBOC, Hereditary Breast and Ovarian Cancer of HBOC-related cancer than in patients with PC with a family history of other cancer or no family history of cancer (22.9% vs. 4.1%; P = 0.014).Genetic counseling was recommended to all patients with gBRCA-positive PC and eight received counseling.

Table 4
Summary of adverse events during the entire period of olaparib maintenance therapy draft.YS, KW, TH, MU, YKai, RT, TY, KM, TN, HU, TI and FF contributed to investigation and writing review and editing.KO contributed to investigation, supervision, and writing review and editing.