Current perspectives in the treatment of small cell lung cancer

DNA-dependent protein kinase content and activity in lung carcinoma cell lines: correlation with intrinsic radiosensitivity

Intrinsic radiosensitivity and rejoining of radiation-induced DNA double-strand breaks (DNA-dsb) were analysed in five lung carcinoma cell lines: U-1285, U-1906, H-69, H-82 and U-1810. RS correlated with both the initial phase of DNA-dsb rejoining, at 15 min (r2 = 0.818) and the late phase, at 120 min postirradiation (r2 = 0.774), the most sensitive cell line (U-1285) showing least dsb rejoining and the most resistant (U-1810) showing most dsb rejoining of all five cell lines studied. As DNA-PK has been recognised as an important molecular component involved in DNA-dsb repair, we analysed content and activity of this kinase. We found that DNA-PK content and activity correlated with RS (r2 = 0.941 and r2 = 0.944, respectively). The lowest DNA-dependent content/activity was found in the most radiosensitive cells, U-1285 and H-69, whilst the highest content/activity was found in the most radioresistant cells U-1810. These results suggest a correlation between RS and DNA-PK content/activity in lung carcinoma cell lines.

Interdigitating versus concurrent chemotherapy and radiotherapy for limited small cell lung cancer

PURPOSE

Sequencing and timing of chemotherapy and radiotherapy for limited small-cell lung cancer (LSCLC) was studied in two consecutive trials.

METHODS AND MATERIALS

In the interdigitating (IDG) trial, three cycles of COPE (cyclophosphamide 750 mg/M2 i.v. Day 1, vincristine 2 mg i.v. Day 8, cisplatin [DDP] 20 mg/M2 Days 1-3, etoposide 100 mg/M2 i.v. Days 1-3), were followed by thoracic radiation therapy (1.5 Gy bid 5-6 h apart, repeated twice at 3-week intervals) to give 45 Gy in 9 weeks; COPE was given during the intervals and for two more cycles. Operable patients had thoracotomy followed by IDG. Prophylactic cranial irradiation (PCI), 2.0 Gy x 15 fractions with a total dose of 30 Gy in 3 weeks, was given to the complete responders (CR) after completion of chemotherapy. In the concurrent (CON) trial, patients received DDP 60 mg/M2 i.v. Day 1, and etoposide 120 mg/M2 i.v. Days 1-3 for four cycles, every 3 weeks, and concurrent thoracic radiation therapy to 45 Gy with either 1.8 Gy daily, for 5 weeks or 1.5 Gy bid for 3 weeks. Prophylactic cranial irradiation (PCI) was given to the complete responders, 2.5 Gy daily for 2 weeks (25 Gy) (approximately 3 months after the initiation of treatment).

RESULTS

The IDG group had 28 evaluable patients with median follow-up of 17.5 months. The CON group had 33 evaluable patients with median follow-up of 21 months. Overall survival rates for IDG patients were 79% at 1 year, 39% at 2 years, 30% at 3 years, and 27% at 4 years compared to 93%, 70%, 51%, and 46%, respectively, for the patients treated with CON (p = 0.01). Loco-regional recurrence (44%) and distant metastasis (48%) was more frequent as the first site of failure in the IDG group compared to the CON group (30% and 30%, respectively). Brain metastases constituted 30% of first metastases with IDG compared to none with CON. Esophagitis was significantly greater with CON. Hematologic and pulmonary toxicity were similar with IDG and CON. One death due to infection was seen in each treatment group.

CONCLUSION

Concurrent chemoradiotherapy appears to be more effective than IDG. Earlier administration of PCI with concurrent chemotherapy and thoracic irradiation may reduce the risk of brain metastasis.