Combining polyamine depletion with radiation therapy for rapidly dividing head and neck tumors: strategies for improved locoregional control

PURPOSE

Locoregional control is adversely affected as clonogens from rapidly proliferating tumors repopulate during a course of radiation therapy. The cytostatic agent alpha-difluoromethylornithine (DFMO) was investigated for its capacity to slow proliferation kinetics in human squamous cell carcinomas (SCC) of the head and neck (H&N), with the ultimate objective of improving locoregional control in rapidly dividing tumors treated with radiation therapy.

METHODS AND MATERIALS

Three human SCC cell lines established from primary H&N tumors were evaluated in vitro (cell culture) and in vivo (SCC tumor xenografts in athymic mice) for the capacity of DFMO to induce growth inhibition. Flow cytometry analysis of SCC tumor growth kinetics and quantitative assessment of polyamine biosynthesis inhibition was performed to verify DFMO activity. DFMO effects on in vitro SCC radiosensitivity using clonogenic survival were also studied.

RESULTS

A noncytotoxic exposure to DFMO (5mM x 72 hours) induced pronounced growth inhibition in all three SCC cell lines (70-90% at 7 days), and induced a 2-3 fold delay in volume doubling time for SCC tumor xenografts when administered orally in the drinking water (1.5%) to athymic mice. Kinetic analysis via flow cytometry confirmed that DFMO produced a lengthening of SCC cell cycle times, but did not alter in vitro radiosensitivity. Inhibition of ornithine decarboxylase (ODC) activity and depletion of endogenous polyamines (putrescine and spermidine), were confirmed in normal tissue (mouse skin) and in human SCC tumor xenografts of athymic mice receiving continuous oral DFMO.

CONCLUSION

These data indicate that antiproliferative agents, such as DFMO, are capable of altering human SCC growth kinetics without altering intrinsic radiosensitivity. Such kinetic modulation may therefore provide a strategy to reduce the adverse impact of tumor cell proliferation during a radiotherapy treatment course for rapidly dividing tumors such as those in the H&N.

Inguinofemoral radiation of N0,N1 vulvar cancer may be equivalent to lymphadenectomy if proper radiation technique is used

PURPOSE

To update a previous retrospective study that compared inguinofemoral irradiation (N = 23) to lymphadenectomy (N = 25) for N0,N1 vulvar carcinoma with more patients and longer follow-up. These results, unlike the recent randomized Gynecologic Oncology Group (GOG study), suggest that radiation is a viable alternative to groin dissection, and the differences may be explained on the basis of irradiation technique.

METHODS AND MATERIALS

Based on a growing body of data supporting control of subclinical nodal disease with irradiation in vulvar cancer, the decision was made to offer patients with squamous cell carcinoma of the vulva and clinically negative groins (N0,N1), either lymphadenectomy or inguinofemoral irradiation based on clinical factors. Because of the acute skin reaction and possible underdosing of deep femoral nodes with electrons as used in the GOG study, opposed photon fields to 50 Gy were used. From 1983 to 1991, 48 patients underwent a radical vulvectomy followed by either lymphadenectomy (Group I, n = 25) or inguinofemoral irradiation (Group II, n = 23).

RESULTS

The actuarial nodal control was 100% in Group I and 91% in Group II (p = 0.14). In addition, there was no difference in cause specific survival at 3 years (96% and 90%, respectively, p = 0.47). The morbidity of lymphadenectomy (Group I) included: 16% lymphedema, 16% seromas, 44% infection, and 68% wound separation. In the irradiated patients (Group II), 16% developed lymphedema and only 9% had a significant skin reaction.

CONCLUSION

Based on this analysis of local control and survival with longer follow-up and more patients, irradiation of the N0, N1 inguinofemoral nodes may be a viable alternative to lymphadenectomy for squamous cell carcinoma of the vulva if proper radiation technique and dose are used. In addition, the acute and delayed morbidity of lymphadenectomy exceeds that of irradiation.

A retrospective review of nodal treatment for vulvar cancer

From 1983 to 1990, 42 clinical N0, N1 patients with invasive squamous cell carcinoma of the vulva underwent surgery for the primary cancer, followed by nonrandomized assignment to either surgery or radiation therapy for nodal management. This is a retrospective analysis reviewing treatment outcome and complications of inguinofemoral dissection versus photon irradiation. Group I (N = 24) underwent either bilateral or unilateral inguinofemoral dissection; Group II (N = 18) underwent bilateral groin irradiation. The 3-year disease-free survival was 84.5% and 79.7% for Group I and II (p = 0.74). The nodal failure rate at 3 years was not significantly different. The postoperative complications in the surgically treated nodes were: 17% seromas, 46% wound infection, and 71% wound separation. Of those patients developing either an infection or wound separation, 41% required daily wound care for more than 2 weeks by a visiting nurse after discharge. Only 1 of 18 (6%) irradiated patients developed a clinically significant skin reaction. The median time for complete skin/wound healing was 8 weeks (range 4-24 weeks) in Group I and 2 weeks (range 2-6 weeks) in Group II. Late postoperative complications in the surgically treated patients included meralgia paresthetica (8%) and lymphedema (12%); 1 (6%) Group II patient developed lymphedema. Based on this limited retrospective review, we conclude that inguinofemoral radiation achieves reasonable local control and may represent an alternative to surgery in selected patients. The acute and delayed morbidity of lymphadenectomy exceeds that of irradiation.