LUAD patients ≥ 60 years of age have now become the type of lung malignancy with the highest proportion of lung malignancies(2, 3).However, there are few previous studies on this group of patients, and 33% of the 248 phase III clinical trials on non-small cell lung cancer from 1980–2010 excluded patients > 65 years of age, so older patients with LUAD are missing both in terms of treatment and prediction of prognosis(15).We hope that by using the huge data in the SEER data to construct an accurate prognostic model for this group of patients, we can better help patients and clinicians make the right choices.Gender, race, marital status, AJCC stage, surgery, radiotherapy, chemotherapy, and distant metastases (bone, brain, liver, and lung) were found to be significant prognostic factors for OS and CSS in this study we conducted by using the COX multifactorial regression model, and a Nomogram was constructed using these prognostic factors.
It has been previously believed that men are more likely than women to have a higher mortality rate from pulmonary malignancies, and in our present study, men had an approximately 30% increased risk of disease progression and death compared to women.A cohort study in Sweden by Cecilia Radkiewicz et al(16).showed that among lung adenocarcinoma subtypes, male patients had a worse prognosis and shorter survival, which is the same result as in our study.An analysis of five phase III clinical trials on chemotherapy for non-small cell lung cancer found that in platinum-based chemotherapy regimens, female patients with lung adenocarcinoma achieved higher ORR and longer survival, as the prognosis of lung adenocarcinoma in females was better than that of males, but this gender difference was not reflected in squamous carcinoma(17).In addition, Carmen Behrens et al(18).pointed out that the number of tumor-associated immune-infiltrating cells in female lung adenocarcinoma patients was higher than that in male lung adenocarcinoma patients, and that such tumor-associated immune-infiltrating cells could bring about better efficacy of treatment with immune checkpoint inhibitors. These two points may be the reason why the prognosis of female lung adenocarcinoma patients is better than that of male patients, and the prognostic differences between genders can be further verified by grouping and comparing the variable of gender using the SEER database.Race is also an important indicator of lung cancer prognosis, and some previous studies have concluded that there is no effect of different races on the prognosis of lung cancer, although the multivariate Cox proportional risk model has been used in most of the previous studies, which ignores the existence of competing risks, thus resulting in unexpected results(19, 20).Whereas the same multivariate Cox proportional risk model was used to construct the Nomogram in our study, we found that there was a difference in survival between races, which is different from previous studies.Differences in marital status among demographic indicators also affect the prognosis of patients with lung adenocarcinoma, and many previous studies have been conducted in this regard.A study based on the SEER database by Dechang Zhao et al(21).showed that single and unmarried patients may have a worse prognosis compared to married individuals and still obtained the same results after correcting for baseline information using the propensity to match score.Another study, also based on the SEER database, on the effect of marital status on survival in lung cancer patients also showed that married patients can have higher cancer-specific survival rates(22).The two studies mentioned above have the same results as those conducted by us, and we speculate that the main reason for this is that married patients may receive more support and care from their family members to help them have a more optimistic mindset, and these may affect the immune microenvironment, which may reduce the mortality rate of the patients(23, 24).
In our modeling, I also incorporated some of the more common clinical factors that affect prognosis. These factors mainly include AJCC staging, surgery, radiotherapy, chemotherapy, and distant metastasis.First of all, the AJCC staging has been revised many times to predict the prognosis of lung malignancies very accurately(25).However, this staging system is not perfect, and the advances in genetic testing and molecularly targeted drug therapy for lung adenocarcinoma in recent years have led to a better prognosis for lung adenocarcinoma than for other types of tumors, which is not taken into account in the AJCC staging system, and the same stage of lung malignant tumors may result in a different prognosis due to different pathologic types(26, 27).That is why we developed this prognostic prediction model. But we still incorporate the AJCC staging system in our model because it still has good prognostic predictive power in the same type of pathology, so we incorporate it.The second independent influencing factor included in our model that affects the prognosis of LUAD in the elderly is the treatment-related factors; current treatments for lung adenocarcinoma include surgery, chemotherapy, radiotherapy, targeted therapy, and immunotherapy, but unfortunately only surgery, chemotherapy, and radiotherapy are available in the SEER database.It is clear that surgery improves the prognosis of patients with lung adenocarcinoma, but the risk of surgery increases significantly in the elderly, so many clinicians try to avoid surgical operations in this group of patients, but with the improvement of surgical operation techniques and anesthesia techniques, the mortality rate due to surgery has been reduced to an acceptable range, so that surgery also improves the patient's prognosis in the elderly(28).A retrospective study on the benefit of surgery for lung cancer in the elderly by Hideomi Ichinokawa(29) and others showed that surgery can be equally beneficial in the elderly, and that differences in staging may lead to a different prognosis in the elderly, which also applies in middle-aged lung cancer and is not unique to elderly patients.When lung adenocarcinoma develops to middle or late stage, only chemotherapy and radiotherapy can be used to prolong the survival of patients in previous treatments. There have been many previous clinical trials showing that platinum-based chemotherapy regimens are more effective in prolonging patient survival and improving survival treatments relative to supportive care, and with the development of third-generation chemotherapeutic agents, such as paclitaxel and gemcitabine, many patients can still benefit from chemotherapy in second- and third-line treatments(30).Radiotherapy, on the other hand, plays a great role in both radical and palliative treatment of non-small cell lung cancer, and can be used for postoperative adjuvant therapy and palliative treatment of advanced metastases, all of which can prolong the overall survival of patients(31).These are also consistent with our model, which is unfortunately a shortcoming given that non-small cell lung cancer has now entered to the era of immunotherapy and targeted therapies, and has even reached the stage of removing chemotherapy from the first line of treatment in intermediate to advanced LUAD, which is missing from the SEER data.Finally, data related to distant metastasis of LUAD were included in our model, and it is well known that patients with metastatic LUAD have a worse prognosis compared to those without metastasis(32).In an observational study conducted in Sweden, a total of 17,431 patients who died of lung cancer were included, and the data showed that brain metastasis (47%), bone metastasis (39%), liver metastasis (35%), and respiratory metastasis (22%) were common sites of metastasis from pulmonary malignancies, and that the median survival after diagnosis of non-metastatic lung cancer was 13 months compared with 5 months for metastatic lung cancer, with only 3 months for patients with hepatic metastases(33).In our study although the baseline baseline material showed a low percentage of patients with metastases, distant metastases were found to be an independent influence on the prognosis of elderly patients with LUAD after screening by COX regression modeling, which is in line with the above retrospective study.
We constructed a predictive model that is more consistent with the prognosis of elderly lung adenocarcinoma patients by using information from the SEER data, and our model is significantly superior to AJCC staging.But this model still has some shortcomings:First, because of missing data within the SEER database, we excluded a portion of the data, which could lead to biased results;Second, our model is missing some factors that are readily available and may be associated with the prognosis of LUAD in the elderly, such as family history, tumor markers, driver mutation status, immunotherapy and targeted therapy information, which we were not able to incorporate because they are not recorded in the SEER database;Finally, the data for this study were all from the SEER database and were not validated against an external population. Therefore a subsequent validation with external data from multiple centers is needed.