October 1, 2021

Antibiotics Show Benefit in Pancreatic Cancer

Examining the link between antibiotics and survival
Some pancreatic cancer patients receiving gemcitabine treatment had improved progression-free survival when taking antibiotics.

This article is part of our October 2021 special issue. Download the full issue here.


Weniger M, Hank T, Qadan M, et al. Influence of Klebsiella pneumoniae and quinolone treatment on prognosis in patients with pancreatic cancer. Br J Surg. 2021;108(6):709-716.


A retrospective study of patients from the Massachusetts General Hospital (USA) and Ludwig-Maximilians-University (Germany)


Data were obtained for 211 patients who underwent preoperative treatment for borderline resectable pancreatic cancer (BRPC) or locally advanced (LAPC) pancreatic cancer followed by pancreatoduodenectomy with curative intent between January 2007 and December 2017, and for whom intraoperative bile cultures were available. Median age of patients was 65.9 years with a median follow up time of 18 months; 108 of these patients were women (51.2%) and mean BMI was 24.8.

Study Medication and Dosage

Patients were treated with a range of different protocols during the decade these data were collected, including FOLFIRINOX alone and with radiation, proton-beam therapy and capecitabine, and gemcitabine in combination with various other chemotherapy drugs.

Patient records were screened for postoperative treatment with quinolone antibiotics, either intravenous or oral. Patients who received any dose for any duration at any time between surgery and death were considered to have had quinolone treatment. About half of the patients (n=104) had been treated with quinolones.

Associations between tumor characteristics, survival data, antibiotic use, and results of intraoperative bile cultures were investigated. Survival was analyzed using Kaplan-Meier curves and Cox regression analysis.

Outcome Measures

The primary outcomes examined were overall survival (OS) and progression-free survival (PFS). These measures were examined in light of the patients’ demographic data and preoperative treatments, plus additional adjuvant treatments. Bile microbiota were assessed using intraoperative cultures, and corresponding resistance patterns were analyzed. These outcomes were compared between those who had received quinolone antibiotics and those who had not.

Key Findings

An increasing number of pathogen species found in intraoperative bile cultures was associated with a decrease in PFS (-1.9 months per species found; P=0.009).

Overall, 48 different pathogens were cultured and identified from the bile samples obtained during surgery. Of these, only Klebsiella pneumoniae, which was cultured in 73 patients, was associated with reduced PFS (16.5 vs 20.7 months in patients who tested positive and negative for K. pneumoniae respectively; P=0.032). Patients with K. pneumoniae had larger tumors than patients without (mean 29.9 mm vs 23.7 mm; P=0.003).

Gut microbiota play a role in the antitumor response and influence long-term survival.

Adjuvant treatment with gemcitabine improved PFS in patients who were negative for K. pneumoniae (26.2 vs 15.3 months; P=0.039), but not in those who tested positive (19.5 vs 13.2 months; P=0.137). Quinolone treatment was associated with improved median overall survival (OS) independent of K. pneumoniae status (48.8 vs 26.2 months; P=0.006) and among those who tested positive for K. pneumoniae (median not reached versus 18.8 months; P=0.028). Patients with quinolone-resistant K. pneumoniae had shorter PFS than those with quinolone-sensitive K. pneumoniae (9.1 vs 18.8 months; P=0.001).

K. pneumoniae appears to promote chemoresistance to adjuvant gemcitabine, and quinolone treatment is associated with improved survival.

Practice Implications

Before we consider this current research by Weniger et al, we should step back and review an earlier study for context—a paper by Leore Geller and colleagues from the Weizmann Institute, which was published in Science in September 2017.1 Geller et al reported that certain bacteria make an enzyme that inactivates the chemotherapy drug gemcitabine (Gemzar™). Gemcitabine is used to treat patients with pancreatic, lung, breast, and bladder cancers.

It seems bacteria, particularly gammaproteobacteria, may produce an enzyme called cytidine deaminase (CDD) that inactivates gemcitabine. Tumor cells normally sensitive to gemcitabine are resistant to treatment when grown with bacteria that produce this enzyme. Geller demonstrated this both in vitro and ex vivo. In mice infected with CDD-producing bacteria, the quinolone antibiotic ciprofloxacin both eliminated the bacteria and ensured a marked antitumor effect from gemcitabine. Tumors in control-mice untreated with antibiotics continued to grow, unhindered by gemcitabine.

Geller turned from mice to humans and questioned how often similar bacteria might pose a problem in cancer treatment. Samples from 113 patients with pancreatic ductal adenocarcinoma (PDAC) were tested using bacterial DNA to see how many tumors contained CDD-producing bacteria. Of the 113 samples, 86 (76%) did. Of 20 samples taken from healthy patients, only 3 (15%) produced CDD.

This new study by Wenger advances our knowledge a few steps.

Protocols for treating pancreatic cancer have shifted in recent years with the publication of 2 studies, a 2020 Dutch study by Versteijne et al and a 2018 Korean study by Jang et al.2,3 It is now standard for chemotherapy and radiation to precede surgery. Such presurgical treatment often shifts disease status to allow potentially curative surgery afterwards. It does often require biliary drainage and stenting, and the combination of stenting and chemotherapy alters the bile microbiome, increasing likelihood of bacterial growth.4 Goel reported in 2019 that when comparing 83 patients who received neoadjuvant treatment with 89 patients who only underwent surgery, the neoadjuvant group were almost twice as likely to have Enterococci and Klebsiella growth in their bile (Enterococci 45 vs 22%, P<0.01; Klebsiella 37 vs 19%, P<0.01).5 Gut microbiota play a role in the antitumor response and influence long-term survival.

Fecal transplants from humans into mice have shown that modulation of the tumor biome affects tumor growth and the natural history of this disease.6

There are 3 take homes from this study that add to our understanding:

  1. Increasing biodiversity of bile pathogens correlates with reduced PFS.
  2. K. pneumoniae decreases the benefit gained from gemcitabine treatment.
  3. Pre-gemcitabine quinolone therapy may restore benefit from gemcitabine and prolong survival.

Bile bacterial diversity

The bile culture findings were surprising. Only 10% of the patients (n=21) had sterile bile. The remaining patients had positive bile cultures and the median number of bacteria found was 3. For each additional species found, there was nearly a 2-month decrease in PFS (-1.9% months per species; P=0.009). The more biodiversity found in the bile, the worse the outcome. This is different than we might have guessed, as greater diversity within most systems, including tumors of the pancreas, is considered desirable.

Overall, 48 different pathogens were identified in the bile, but only K. pneumoniae, which was found in 73 patients, was associated with reduced PFS. Patients with K. pneumoniae had larger tumors than patients without. No differences were found in nodal (N) status, perineural invasion, vascular invasion, ratio of patients with borderline resectable and locally advanced disease, tumor stage, or margin status. There were also no differences in morbidity or mortality.

While K. pneumonia status did not predict OS or PFS in patients treated with FOLFIRINOX or proton beam therapy and capecitabine, it did make a significant difference in those treated with gemcitabine. Gemcitabine treatment did not improve PFS in patients who tested positive for K. pneumoniae.

However, in the K. pneumoniae–negative patients, treatment with gemcitabine improved PFS. No effect was seen for OS.

Bottom line: Postoperative quinolone is associated with improved postoperative survival in both the overall population and patients positive for Klebsiella pneumoniae.

Of the patients in this study, 104 received quinolones and 106 did not. Treatment with quinolones was associated with improved OS and PFS. In patients who were positive for K. pneumoniae, quinolone therapy was associated with improved OS but not PFS. In the K. pneumoniae-negative group, mean survival was nearly twice as long in the patients who received quinolones, but this fell short of statistical significance. This might hint that the antibiotics provided benefits in addition to blocking K. pneumoniae interference with gemcitabine’s efficacy. Previous evidence suggests that quinolones may have an independent anticancer effect.7-9

While gemcitabine has in recent years been a mainstay in the treatment of pancreatic cancer, it is also used to treat non-small cell lung, bladder, sarcoma, breast, and ovarian cancers. There is little reason to think that this same relationship between K. pneumoniae and the drug’s efficacy will not also hold true for these cancers.

Many of us have seen K. pneumoniae reported present on stool microbiology test results. These bacteria vary widely in virulence and antibiotic sensitivity.10 It is unclear how predictive stool cultures are of bile infection with K. pneumoniae, although the idea of substituting stool testing is tempting. Although Weniger et al used bile samples obtained during surgery, identifying K. pneumoniae in the stool may be equally predictive or it may have little correlation. The risk of false negatives might also suggest that it is more efficacious to assume all patients are positive for K. pneumoniae and treat them with quinolones prior to gemcitabine. Time might also favor such an approach as gemcitabine treatment might be initiated quickly after diagnosis—sooner than a stool test result could be obtained.

It may well be that in the near future it will become common practice for at least some medical oncologists to prescribe a course of antibiotics prior to a treatment course of gemcitabine based on these findings. In such a situation we might consider the addition of the botanical extract berberine into the treatment plan. Berberine has been reported to have a synergistic effect with quinolone antibiotics against drug-resistant K. pneumoniae.11 The knowledge that berberine may also act against pancreatic cancer cells12,13 and may sensitize these cells to gemcitabine14 only adds encouragement to incorporate it into the protocols for these patients. Although some patients may want to use berberine in place of quinolones, it is important that they understand berberine acts as an adjuvant, not as a substitute.

This discussion has focused on one specific aspect of how the microbiome impacts treatment of pancreatic cancer. Evidence continues to accumulate that pancreatic cancer is greatly impacted by microbiota far more than was once assumed. There are multiple other interactions documented between gut microbiota and adjuvant effectiveness in treating PDAC.15 Further developments in understanding about these interactions should be expected in the future.16

Categorized Under


  1. Geller LT, Barzily-Rokni M, Danino T, et al. Potential role of intratumor bacteria in mediating tumor resistance to the chemotherapeutic drug gemcitabine. Science. 2017;357(6356):1156-1160.
  2. Versteijne E, Suker M, Groothuis K, et al. Preoperative chemoradiotherapy versus immediate surgery for resectable and borderline resectable pancreatic cancer: results of the Dutch Randomized Phase III PREOPANC Trial. J Clin Oncol. 2020;38(16):1763-1773.
  3. Jang JY, Han Y, Lee H, et al. Oncological benefits of neoadjuvant chemoradiation with gemcitabine versus upfront surgery in patients with borderline resectable pancreatic cancer: a prospective, randomized, open-label, multicenter phase 2/3 trial. Ann Surg. 2018;268(2):215-222.
  4. Scheufele F, Aichinger L, Jäger C, et al. Effect of preoperative biliary drainage on bacterial flora in bile of patients with periampullary cancer. Br J Surg. 2017;104(2):e182-e188.
  5. Goel N, Nadler A, Reddy S, Hoffman JP, Pitt HA. Biliary microbiome in pancreatic cancer: alterations with neoadjuvant therapy. HPB (Oxford). 2019;21(12):1753-1760.
  6. Riquelme E, Zhang Y, Zhang L, et al. Tumor microbiome diversity and composition influence pancreatic cancer outcomes. Cell. 2019;178(4):795-806.e12.
  7. Aranha O, Wood DP Jr, Sarkar FH. Ciprofloxacin mediated cell growth inhibition, S/G2-M cell cycle arrest, and apoptosis in a human transitional cell carcinoma of the bladder cell line. Clin Cancer Res. 2000;6(3):891-900.
  8. Herold C, Ocker M, Ganslmayer M, Gerauer H, Hahn EG, Schuppan D. Ciprofloxacin induces apoptosis and inhibits proliferation of human colorectal carcinoma cells. Br J Cancer. 2002;86(3):443-448.
  9. El-Rayes BF, Grignon R, Aslam N, Aranha O, Sarkar FH. Ciprofloxacin inhibits cell growth and synergises the effect of etoposide in hormone resistant prostate cancer cells. Int J Oncol. 2002;21(1):207-211.
  10. El Fertas-Aissani R, Messai Y, Alouache S, Bakour R. Virulence profiles and antibiotic susceptibility patterns of Klebsiella pneumoniae strains isolated from different clinical specimens. Pathol Biol (Paris). 2013;61(5):209-216.
  11. Zhou XY, Ye XG, He LT, et al. In vitro characterization and inhibition of the interaction between ciprofloxacin and berberine against multidrug-resistant Klebsiella pneumoniae. J Antibiot (Tokyo). 2016;69(10):741-746.
  12. Park SH, Sung JH, Kim EJ, Chung N. Berberine induces apoptosis via ROS generation in PANC-1 and MIA-PaCa2 pancreatic cell lines. Braz J Med Biol Res. 2015;48(2):111-119.
  13. Pinto-Garcia L, Efferth T, Torres A, Hoheisel JD, Youns M. Berberine inhibits cell growth and mediates caspase-independent cell death in human pancreatic cancer cells. Planta Med. 2010;76(11):1155-1161.
  14. Abrams SL, Lertpiriyapong K, Yang LV, et al. Introduction of WT-TP53 into pancreatic cancer cells alters sensitivity to chemotherapeutic drugs, targeted therapeutics and nutraceuticals. Adv Biol Regul. 2018;69:16-34.
  15. Zhang X, Liu Q, Liao Q, Zhao Y. Pancreatic cancer, gut microbiota, and therapeutic efficacy. J Cancer. 2020;11(10):2749-2758.
  16. Wei MY, Shi S, Liang C, et al. The microbiota and microbiome in pancreatic cancer: more influential than expected. Mol Cancer. 2019;18(1):97.