Combined Chemoradiotherapy in Small Cell Lung Cancer

Injectable (-)-gossypol-loaded Pluronic P85 micelles for cancer chemoradiotherapy

PURPOSE

The aim of tumor-specific chemoradiotherapy is to achieve synergistic anticancer effects with clinically acceptable toxicity. Our previous studies showed that Pluronic P85 augments radiation cancer cell killing of (±)-gossypol in vitro. In this study, the radiosensitizing effect of (-)-gossypol, more potent Bcl protein inhibitor, with Pluronic P85 was investigated.

MATERIALS AND METHODS

The inhibitory effect of (-)-gossypol solubilized Pluronic P85 with 0-8 Gy of radiation on clonogenic survival rate of A549 human lung adenocarcinoma cells was investigated in vitro. The anticancer effect of (-)-gossypol-solubilized Pluronic P85 with fractionated radiation of 15 Gy was assessed by A549 tumor-bearing mice.

RESULTS

(-)-Gossypol-loaded Pluronic P85 was found to be a more potent radiosensitizer in vitro. Pluronic P85 increased the anti-proliferative activity of (-)-gossypol against A549 cells (82 ± 42 versus 190 ± 60 nM). In addition, the combination of P85 and (-)-gossypol effectively reduced clonogenic survival of A549 cells: (11 ± 5%) compared to (-)-gossypol and P85 alone (62 ± 27% and 93 ± 13%, respectively), and enhanced radiation cancer cell killing. In vivo, P85 (200 mg/kg/day) and (-)-gossypol (15 mg/kg/day) could be safely injected intravenously over 5 days and enhanced radiation-related tumor control in an A549 xenograft model.

CONCLUSION

Pluronic P85 and (-)-gossypol act as a novel dual agent radiosensitizer and holds promise as a chemoradiotherapeutic strategy.

Small cell lung cancer: treatment review

Lung cancer was relatively uncommon at the turn of the 20th century, and has increased in prevalence at alarming rates, particularly because of the augmented trend in smoking, so that it is now the most common cause of cancer death in the world. As almost a quarter of these cancers are of small cell in origin, it seems only appropriate that small cell lung cancer receives ample attention, rather than seemingly to have been overlooked over the last 10-15 years. Despite its generally late presentation and high risk of dissemination, it is exceptionally sensitive to chemo-radiotherapy. This review looks at the diverse options of treatment that have been used over the last few years and tries to highlight the best available. As more than 50% of patients diagnosed with lung cancer are over 70 years of age and various studies have shown that older people respond just as well as their younger counterparts, with similar results in response rates, toxicity and outcomes, it is imperative that the older generation are not disregarded in terms of age being a contraindication to therapy.

Small cell lung cancer

Small cell lung cancer accounts for 13-15% of all lung cancer worldwide. There has been a decrease in the number of cases, with no clear explanation, except probably to changing in smoking habits in the last two decades. In the early eighties, it became clear that SCLC was an extremely sensitive tumor as to radiation as to chemotheraputic agents. With cisplatinum etoposide combinations or cyclophosphamide, anthracycline and vincristine/etyoposide regimens responses were observed in 50-70%, with 20-30% complete remissions in extensive disease. For limited stage patients chemotherapy associated with thoracic radiation was able to produce a cure rate of 10-20%. The addition of prophylactic brain irradiation to limited stage cases has reduced mortality by a factor of nearly 5%. But despite these early good results no breakthrough came later on, and in the last decade or so, we are still facing this plateau. New agents have recently been included in the therapeutic armamentarium, such as gemcitabine, irinotecan, paclitaxel. This fact has allowed many patients to receive a relatively active second line therapy, but the overall survival remains unchanged. Targeted therapies are undergoing some evaluations, but the data are too premature and so far quite discouraging. At the present time there is a urgent need to improve clinical research in this somehow forgotten disease.