Timing Liposomal Irinotecan in Advanced Pancreatic Cancer

Prior exposure to conventional irinotecan does not affect survival in patients with advanced pancreatic ductal adenocarcinoma (PDAC) who are subsequently treated with the liposomal formulation nanoliposomal irinotecan (nal‐IRI), according to a meta-analysis of real-world studies.

“The selection of later lines of chemotherapy regimens should be based on the differential safety profile, patient status, the cost of treatment, and health‐related quality of life,” reported lead author Amol Gupta, MD, from the Sidney Kimmel Comprehensive Cancer Center at the Johns Hopkins Hospital in Baltimore.

The findings, reported in Cancer on July 10, 2024, are “noteworthy with respect to calling attention to this important situation and the role of a new drug in the PDAC pharmacologic armamentarium,” commented Vincent J. Picozzi, MD from the Division of Hematology‐Oncology, Virginia Mason Medical Center, in Seattle, in an accompanying editorial.

Treatment of PDAC remains a challenge, the authors noted, as most diagnoses occur at a metastatic or locally advanced stage at which treatments provide only modest benefits and significant toxicities.

The introduction of the first‐line FOLFIRINOX regimen (fluorouracil [5‐FU], leucovorin [LV], irinotecan [IRI], and oxaliplatin) and gemcitabine plus nanoparticle albumin‐bound (nab)‐paclitaxel “has improved the survival of patients with advanced PDAC and increased the number of patients eligible for subsequent therapies” beyond the first-line setting, according to the authors. But survival benefits with FOLFIRINOX and gemcitabine‐based therapy remain poor, with median overall survival (OS) of 6 and 7.6 months, respectively, they noted.

Timing Liposomal Irinotecan

The liposomal formulation of IRI has resulted in improved pharmacokinetics and decreased toxicity, but use of this new formulation in later lines of therapy is sometimes limited by concerns that prior exposure to conventional IRI in FOLFIRINOX might produce cross-resistance and reduce the benefit of nal-IRI, the authors explained.

To examine this question, the researchers included eight retrospective chart reviews published up until April 2023 that included a total of 1368 patients who were treated with nal-IRI for locally advanced or metastatic PDAC (five studies) or locally advanced or metastatic PDAC (three studies). Patients ranged in age from 57.8 to 65 years, with the proportion of male patients ranging from 45.7% to 68.6%. The sample sizes of the studies ranged from 29 to 675 patients, with a follow-up range of 6-12.9 months.

Between 84.5% and 100% of patients had received two or more prior lines of therapy, with prior IRI exposure ranging from 20.9% to 100%. In total, 499 patients had prior IRI exposure, mostly in the first-line setting. When reported, most patients gave the reason for IRI discontinuation as disease progression.

Across all patients, the pooled progression-free survival (PFS) and OS were 2.02 months and 4.26 months, respectively, with comparable outcomes in patients with prior IRI exposure compared with those without: PFS (hazard ratio [HR], 1.17; 95% CI, 0.94-1.47; P = .17) and OS (HR, 1.16; 95% CI, 0.95-1.42; P = .16), respectively. This held true regardless of whether patients had experienced progressive disease on conventional IRI. Specifically, the PFS and OS of patients who discontinued conventional IRI because of progressive disease were comparable (HR, 1.50 and HR, 1.70) with those of patients who did not have progressive disease.

The authors reported there was substantial variation in predictors of nal-IRI outcomes among the studies examined. One study reported a numerical but not statistically significant better PFS and OS associated with longer IRI exposure and a higher cumulative dose of prior IRI. Two studies suggested worse PFS and OS associated with later treatment lines of nal-IRI, although adjusted HR did not reflect this. Sequence of treatment was a significant predictor of outcome, as were surgery and metastatic disease, bone and liver metastases, serum albumin < 40 g/L, a neutrophil‐to-lymphocyte ratio > 5, and an elevated baseline carbohydrate antigen 19‐9 level.

“There are several reasons to consider why nal‐IRI may be effective after standard IRI has failed to be so,” commented Picozzi, suggesting pharmacokinetics or an improved tumor tissue/normal tissue exposure ratio as possible explanations. “However, as the authors point out, the results from this pooled, retrospective review could also simply be the result of methodological bias (eg, selection bias) or patient selection,” he added.

“Perhaps the best way of considering the results of the analysis (remembering that the median PFS was essentially the same as the first restaging visit) is that nal‐IRI may be just another in a list of suboptimal treatment options in this situation, he wrote. “If its inherent activity is very low in third‐line treatment (like all other agents to date), the use and response to prior standard IRI may be largely irrelevant.”

Consequently, he concurs with the authors that the selection of third-line treatment options and beyond for advanced APDAC should not be influenced by prior IRI exposure.

First-Line Liposomal Irinotecan Approved

In February, the US Food and Drug Administration (FDA) approved nal-IRI (Onivyde) as part of a new first-line regimen for first-line metastatic PDAC. In the new regimen (NALIRIFOX), nal-IRI is substituted for the conventional IRI found in FOLFIRINOX, boosting the cost more than 15-fold from around $500-$7800 per cycle.

The FDA approval was based on the results of the NAPOLI-3 study, which did not compare outcomes of NALIRIFOX with FOLFIRINOX, but rather, compared first-line nal-IRI with the combination of nab‐paclitaxel and gemcitabine. The study showed longer OS (HR, 0.83; 95% CI, 0.70-0.99; P = .04) and PFS (HR, 0.69; 95% CI, 0.58-0.83; P < .001), with first-line nal-IRI.

The absence of a head-to-head comparison has some oncologists debating whether the new regimen is a potential new standard first-line treatment or whether the cost outweighs the potential benefits.

One study author Dung Le reported grants/contracts from AbbVie, Bristol Myers Squibb, Curegenix, Medivir, Merck, and Nouscom; personal/consulting fees from Bayer, Catenion, G1 Therapeutics, Janssen Pharmaceuticals, Merck, Merus, Nouscom, Regeneron, Sirtex Medical Inc., Tango Therapeutics, and Tavotek Biotherapeutics; and support for other professional activities from Bristol Myers Squibb and Merck outside the submitted work.

Another study author Michael Pishvaian reported personal/consulting fees from Astellas Pharma, AstraZeneca, IDEAYA Biosciences, Inc., Merck, Merus, Moderna, RenovoRx, Seattle Genetics, Inc., and TriSalus Life Sciences outside the submitted work.

The remaining authors and Picozzi disclosed no conflicts of interest.