Clinical Management of Obese Cancer Patients: New Ideas for Conventional Treatment and Comprehensive Weight Loss

III. Treatment and Prognosis 1. Conventional Treatment of Tumors Common tumor treatment methods include surgery, chemotherapy, radiotherapy, and interventional therapy. Early-stage tumors are mostly treatable surgically, with different treatment methods depending on the location of the tumor. Treatment for advanced-stage tumors includes: local surgical resection to relieve compression, obstruction, and tracheal obstruction; chemotherapy and targeted therapy (different targeted drugs are used for different tumor systems); radiotherapy (radiotherapy can be radical, palliative, adjuvant, and prophylactic); interventional therapy, immunotherapy, and traditional Chinese medicine. Interventional therapy includes bronchial or hepatic artery perfusion therapy, transbronchial or arteriovenous intervention; immunotherapy drugs are used for different tumor systems. 2. New ideas for the treatment of obese patients with tumors (1) Surgical treatment of obesity and tumors: There is disagreement about the role of obesity in the long-term and long-term outcomes of surgery for tumor patients undergoing surgery. However, maintaining a normal BMI, choosing less invasive surgical methods such as laparoscopy, and strict postoperative monitoring and complication management are all effective ways to reduce the postoperative mortality and complication risk of obese tumor patients. (2) Chemotherapy of obesity and tumors: The dosage of cytotoxic chemotherapy drugs is calculated based on body surface area (BSA). BSA is calculated based on height and weight. Therefore, the BSA of obese patients is often larger. It is recommended to use the ideal BSA calculated based on ideal weight for drug administration. Studies have found that receiving full dose of chemotherapy based on actual BSA in obese tumor patients does not lead to greater adverse reactions. Therefore, it is recommended to administer full dose of cytotoxic chemotherapy drugs to obese tumor patients. However, in clinical practice in my country, when the actual BSA is ≥2.0m², it is still uniformly calculated as 2.0m² due to concerns about adverse reactions. However, some studies have also shown that obese patients' tumor cells are less responsive to chemotherapy and have higher drug resistance. The mechanism is mostly related to changes in pharmacokinetics, chronic inflammation, and dysregulation of tumor-associated adipokines. For cancer patients receiving chemotherapy, fat can act as a protective factor to accumulate energy and improve tolerance, but it can also induce and weaken the responsiveness of tumor cells to chemotherapy drugs, resulting in drug resistance. In recent years, many studies have shown that reduced muscle mass is associated with poor prognosis in cancer patients receiving chemotherapy. For obese cancer patients, the tumor-specific response should not be considered alone, but the patient's underlying diseases and overall prognosis should be comprehensively assessed to provide reasonable suggestions for their weight management. For patients with normal or underweight weight, moderate weight gain can ensure chemotherapy tolerance; for obese patients, moderate weight loss and appropriate exercise can reduce drug resistance induced by adipose tissue, enhance muscle strength, reduce muscle loss, and improve prognosis. (3) Obesity and targeted therapy and immunotherapy for tumors: Targeted therapy seems to have different situations in the treatment of different tumors. The relationship between targeted therapy efficacy and obesity varies among different populations, different tumors, different subtypes and stages of the same tumor, and different treatments for the same tumor. This may be related to hormone levels, treatment methods, BMI, BM cut-off values, and other mechanisms, and further exploration is needed. Some studies have found that metformin can significantly inhibit tumor growth when used in a fasting state, and proposed that the PP2A-GSK3β-MCL-1 pathway may be a new target for tumor treatment. Energy restriction leads to insufficient energy supply, thereby reducing the body's metabolism and playing an anti-cancer role. This study found that intermittent fasting can not only regulate metabolism in the body and increase the effect of chemotherapy, but also protect patients from the toxic side effects of chemotherapy, which is helpful for clinical treatment. Therefore, the combined use of intermittent fasting and metformin can be used to explore the therapeutic potential of tumors. (4) Complex effects of obesity on tumor treatment outcomes: Obesity has different effects on tumor treatment and prognosis in different tumors, different subtypes and stages of the same tumor, different treatment methods, different races, and different genders/ages. Some studies have shown that obesity is associated with higher complication rates, all-cause mortality, tumor-specific mortality, shorter survival, and poorer drug response rates. Paradoxically, some studies have shown that overweight or obese individuals often achieve better survival benefits compared to those of normal weight-this is the "obesity paradox" in oncology. It is important to note that conclusions regarding the effects of obesity on cancer treatment and prognosis do not apply to healthy individuals. Obesity remains a risk factor for cancer development, and proper weight management remains an effective way to mitigate the risk. With the rapid advancements in early cancer screening methods and increased awareness of primary prevention, the detection rate of early-stage cancer will rise, making research on the relationship between obesity and cancer prognosis in early-stage cancer patients significant. Furthermore, weight management for obese patients should be based on the patient's baseline condition, considering not only cancer treatment efficacy but also the impact of obesity on all-cause prognosis.