PLD has its unique mechanism[7–10]: 1, low immunogenicity, little side effects, phospholipid molecules are amphiphilic molecules, improve solubility; 2, almost 100% of liposomes exist in the form of liposomes in the blood circulation; 3, after liposomes are biodegraded, the drug is released slowly, and the circulation time of the drug in the body(T1/2 55–70 h); 4, reasonable liposome size-the average particle size is about 90 nm. 5.EPR effect, tumor vascular permeability increases, and liposomes are smaller, which can pass through defective blood vessels, thus increasing the local drug concentration in tumor tissue about 20 times that of common doxorubicin.
The toxicity and side effects, especially cardiotoxicity, have been significantly reduced, which may be due to the low peak concentration of free doxorubicin in plasma after administration of PLD and the trend of accumulation of liposome drugs in the myocardium[8]. It was not until a significantly higher lifetime dose was reached that the cardiotoxicity of the nanoparticle preparation PLD was observed[11, 12]. However, Sarah E. Gill [13] pointed out that PLD has no obvious cardiotoxicity, which is proved by the stability of LVEF even after high cumulative dose treatment. In the absence of other risk factors, routine monitoring of LVEF does not seem to be necessary or cost-effective.
However, PLD has its unique side effects, especially mucositis and palmar-plantar erythrodysesthesia (PPE). Besides, some patients may have hypersensitivity reaction(HSR), that is, acute hypersensitivity (infusion) reactions referred to as complement activation-related pseudoallergy (CARPA)[14–16], To minimize HSR to PLD, an initial reduced rate of infusion of 0.1–0.2 mg/min of PLD is warranted. In the event of HSR, alternative therapy must be privileged, and if necessary, careful rechallenge with PLD may be attempted, however, relapse of HSR may occur[17].
The tolerance of the drug has been increased, and the mechanism of action has been improved. what about the curative effect? At present, there is no clear evidence that PLD has a better curative effect than traditional doxorubicin. Meta-analysis showed [18] that in the case of ovarian cancer, the PFS benefit of the PLD-based regimen was significant, although the OS did not improve. Another meta-analysis[19] showed that the efficacy of liposome (liposome anthracyclines, liposome cisplatin, etc.) was not different from that of conventional chemotherapy, and even the subgroup of liposome doxorubicin did not show an obvious advantage. At the same time, this article conducted a meta-analysis of 11 preclinical studies of liposome anthracyclines. In contrast to the clinical results, animal studies showed that the survival rate of mice treated with PLD was significantly higher than that of traditional anthracyclines (HR0.39; 95%CI 0.27–0.56). It seems that the potential of PLD has not been fully exploited.
At present, it has been widely used in hematological tumors, ovarian cancer, and breast cancer[12, 20–23]. However, PLD has not been widely used in the treatment of gastric cancer. A phase II clinical trial in 2001[24] suggested that liposome doxorubicin alone had no significant antineoplastic activity in gastric cancer. Recchia[25] et al used PLD combined with oxaliplatin in the salvage treatment of gastric cancer, median PFS 5.8 months, OS 9.2 months. In 2005, the phase II clinical trial of Gnad-Vogt et al[5] proved that PLD combined with mitomycin and fluorouracil achieved a response rate of 47% in the first-line treatment of gastric cancer, with a median PFS of 8.4 months and an OS 14.7 months. In 2011, Cascinu et al[6] conducted a phase II clinical trial in which PLD, cisplatin, and 5-FU were used in the first-line treatment of gastric cancer, compared with mitomycin C, cisplatin, and 5-Fu. ORR, TPP, and OS were superior to the control group. This trial was once cited by NCCN guidelines and later deleted. In the past nine years, there has been no further clinical study, and the treatment of gastric cancer has been developed. At present, XELOX or SOX regimen is the first choice, while the DCF regimen is recommended in NCCN guidelines for patients with the good general condition and frequent monitoring of side effects. Thus, is there a regimen that is safe and more effective than XELOX or SOX?
In the D-SOX group,we reduced the dose of oxaliplatin regimen from 130 mg/m2 to 85 mg / m2, plus pegylated liposome doxorubicin, 25 mg/m2, thus reducing the cumulative dose of oxaliplatin, thus reducing the possibility of peripheral neurotoxicity. At the same time, the cumulative dose of PLD, even after six standard cycles of chemotherapy, was only 150 mg/ m2. At this dose level, no serious adverse reactions were observed, including cardiotoxicity, mucositis, etc., and the incidence of alopecia was rare. There are statistical differences in PFS and OS between the two groups, the root cause of which lies in the chemotherapy regimen, but it may also be related to the better economic conditions of patients in the D-SOX group and better palliative treatment (PLD is not included in medical insurance). In previous years, targeted therapy was not widely used, and only 2 cases in each group received targeted therapy. There was no significant difference in ORR and DCR between the two groups, which was related to the small sample size and the termination of treatment without evaluating the curative effect of some patients. On the other hand, the lack of follow-up treatment also reduces the impact of differences in follow-up treatment on OS.
With the development of molecular targeted therapy and immunotherapy, there is a significant decrease in the number of patients with chemotherapy exceeding the second line in clinical practice, so the use of as many effective drugs as possible in first-line and second-line therapy may benefit patients to the greatest extent. Of course, side effects must be considered. Therefore, the low-dose combination of the three drugs may be one of the options.
Of course, this article is only a retrospective study and the number of cases is relatively small. The selection of cases does not strictly follow the principle of randomization, so there may be bias. It is hoped that there will be well-designed clinical trials to verify the effectiveness of the D-SOX regimen in the future.
In conclusion, pegylated liposomal doxorubicin combined with S-1 and low-dose oxaliplatin might be a safe and more effective treatment for advanced gastric cancer