Lomustine vs Temozolomide: Comprehensive Comparison of Efficacy and Safety in Glioma Treatment

　　Lomustine and temozolomide belong to the alkylating agent class of antineoplastic drugs,classified as nitrosoureas and imidazotetrazines respectively.Both can be metabolized in the body to generate cytotoxic active alkylating groups,which induce DNA cross-linking and strand breaks,interfere with DNA replication and transcription in tumor cells,and ultimately exert anti-tumor effects.As a first-generation oral nitrosourea,lomustine is highly lipophilic and can effectively cross the blood-brain barrier,mainly used for the treatment of gliomas and Hodgkin lymphoma.Temozolomide,as a second-generation oral alkylating agent,also has excellent blood-brain barrier penetration and is currently the standard first-line treatment for glioblastoma.Although their mechanisms of action are similar,there are significant differences in clinical efficacy,side effect profiles,and application scopes.

　　In the treatment of newly diagnosed glioblastoma,temozolomide combined with radiotherapy followed by sequential single-agent adjuvant therapy is the globally recognized standard regimen.Data from a landmark large phase III clinical trial(EORTC 26981)showed that patients receiving temozolomide plus radiotherapy had a median overall survival of 14.6 months,compared with 12.1 months in the radiotherapy alone group;the 2-year survival rates were 26%and 10%respectively,with a statistically significant difference.Although lomustine was once used in glioma treatment,it lacks high-quality evidence-based medical support of the same level.In a randomized controlled trial,the median survival of lomustine combined with radiotherapy was 12.5 months,which was not superior to temozolomide.For recurrent glioblastoma,the progression-free survival of both drugs as monotherapy is similar,approximately 2-3 months,but temozolomide shows better efficacy in patients with MGMT promoter methylation,with an objective response rate of about 20%compared to about 10%for lomustine.Overall,temozolomide is superior or equivalent to lomustine in both newly diagnosed and recurrent glioblastoma.

　　In the treatment of other tumor types,the clinical positioning of the two drugs differs.In the field of Hodgkin lymphoma,lomustine occupies an irreplaceable position as an important component of the BEAM conditioning regimen before hematopoietic stem cell transplantation,while temozolomide has relatively limited applications in lymphoma treatment.In the treatment of melanoma brain metastases,both drugs show certain anti-tumor activity,but the intracranial objective response rate of temozolomide is about 15%,slightly higher than that of lomustine at 10%.Overall,temozolomide has a wider range of clinical applications and more sufficient evidence-based medical evidence.

　　In terms of tolerability and safety,the side effects of lomustine are more severe and some are irreversible.The main differences between the two are reflected in the following aspects.First,myelosuppression:lomustine can cause delayed and cumulative thrombocytopenia and neutropenia,with the nadir usually occurring 4-6 weeks after administration,lasting up to 2 weeks,and the recovery rate of bone marrow function gradually slows down with increasing treatment cycles;while temozolomide causes milder myelosuppression,with the nadir occurring 3-4 weeks after administration and usually recovering within 1 week.Second,pulmonary toxicity:approximately 10%of patients receiving long-term lomustine develop interstitial pneumonitis or pulmonary fibrosis,which can be fatal;while temozolomide has almost no significant pulmonary toxicity.Third,hepatotoxicity:lomustine can occasionally cause severe liver injury such as sinusoidal obstruction syndrome;temozolomide-induced liver enzyme elevation is relatively rare and mostly transient.Fourth,gastrointestinal reactions:both are highly emetogenic drugs,but lomustine has a stronger emetic effect and usually requires a potent antiemetic regimen of aprepitant combined with 5-HT3 antagonists.Fifth,nephrotoxicity:when the cumulative dose of lomustine exceeds 1500mg/m²,it may lead to chronic renal insufficiency;while temozolomide has no significant nephrotoxicity.

　　Based on the above efficacy and safety comparisons,temozolomide has become the first-choice drug for glioma treatment due to its better tolerability and more definite survival benefits.Lomustine is currently mainly used in the following specific clinical scenarios:recurrent glioblastoma after temozolomide resistance,especially in patients with unmethylated MGMT promoter;conditioning regimens before hematopoietic stem cell transplantation;and as an alternative treatment option in regions where temozolomide is not accessible.Clinicians should avoid long-term cumulative use of lomustine,generally not exceeding 6 treatment cycles,and regularly monitor pulmonary function every 3 months.For elderly patients or those with combined renal insufficiency,temozolomide should be preferred.In terms of administration,both are oral preparations,but lomustine should be taken on an empty stomach in a single dose,while temozolomide can be taken on an empty stomach or at bedtime.

　　In summary,in terms of efficacy,temozolomide is significantly superior to lomustine in glioblastoma treatment;in terms of tolerability,temozolomide also has obvious advantages with extremely low incidence of pulmonary and renal toxicity;in terms of side effect profile,lomustine carries special risks of delayed and cumulative hematological toxicity as well as irreversible pulmonary fibrosis.Therefore,in current clinical practice,temozolomide should be preferred,and lomustine should only be considered in the specific clinical situations mentioned above.